refactor: finish refactor of kernel

- use sorted lut and bisect to optimize lut resolver
- add circuit decuper
- add signed diff for response item

README.md

@@ -1,3 +1,17 @@
 # LCR Connector
 
-TODO
+Get the resistor, capacitor, or inductor circuit which has the closest value for your given value within at most 3 devices.
+
+This project is coming from HFUT experiment class where I need to build an active low-pass filter with limited laboratory components.
+So I create this project to help me to find the closest circuit for my given value.
+After a couple of years, I still find it useful, so I decide to refactor it.
+And make it available for everyone in a more convenient way, like GUI and mobile app.
+
+# Todos
+
+- [x] Refactor the legacy version.
+- [x] Add BFS resolver in legacy version to replace LUT resolver.
+- [ ] Use Rust to fully rewrite the legacy version as a library.
+- [ ] Use Rust to create a CLI based on the library created at previous step.
+- [ ] Utilize FLTK to create a GUI in desktop operating system.
+- [ ] Utilize Flutter to create a GUI in mobile operating system.

kernel/.gitignore

@@ -0,0 +1 @@
+/target

kernel/Cargo.lock

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kernel/Cargo.toml

@@ -0,0 +1,6 @@
+[workspace]
+resolver = "3"
+members = ["lcrconn", "lcrconn-cli"]
+
+[workspace.dependencies]
+

kernel/lcrconn-cli/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "lcrconn-cli"
+version = "1.0.0"
+edition = "2024"
+
+[dependencies]
+anyhow = "1.0.103"
+lcrconn = { path="../lcrconn" }
+clap = { version="4.5.48", features=["derive"]}
+strum = "=0.28.0"
+strum_macros = "=0.28.0"

kernel/lcrconn-cli/src/app.rs

@@ -0,0 +1,541 @@
+use crate::cli::{AppConfig, AppResolver};
+use anyhow::Result;
+use lcrconn::{
+    BfsResolver, DeviceKind, LutResolver, Request, Resolver, Response, ResponsePriority,
+    common::{Circuit, CircuitDeviceScale, JointKind, validate_device_value, validate_floating_point},
+    spec::{SpecCatalog, from_human_readable_value, to_human_readable_value},
+    query::MAX_RESPONSE_CNT,
+};
+use std::io::Write;
+use std::str::FromStr;
+use strum_macros::EnumString;
+
+// region: App Utility Enums
+
+/// The command for the main menu.
+#[derive(Debug, Clone, Copy, EnumString)]
+enum MainCmd {
+    #[strum(serialize = "query")]
+    Query,
+    #[strum(serialize = "help")]
+    Help,
+    #[strum(serialize = "exit")]
+    Exit,
+}
+
+/// The device choice for query.
+#[derive(Debug, Clone, Copy, EnumString)]
+enum QueryDeviceChoice {
+    #[strum(serialize = "r")]
+    Resistor,
+    #[strum(serialize = "c")]
+    Capacitor,
+    #[strum(serialize = "l")]
+    Inductor,
+}
+
+impl QueryDeviceChoice {
+    fn to_device_kind(self) -> DeviceKind {
+        match self {
+            Self::Resistor => DeviceKind::Resistor,
+            Self::Capacitor => DeviceKind::Capacitor,
+            Self::Inductor => DeviceKind::Inductor,
+        }
+    }
+}
+
+/// The sort priority for query results.
+#[derive(Debug, Clone, Copy, EnumString)]
+enum QuerySortPriority {
+    #[strum(serialize = "l")]
+    LessDevices,
+    #[strum(serialize = "a")]
+    MoreAccuracy,
+}
+
+impl QuerySortPriority {
+    fn to_response_priority(self) -> ResponsePriority {
+        match self {
+            Self::LessDevices => ResponsePriority::LessDevices,
+            Self::MoreAccuracy => ResponsePriority::MoreAccuracy,
+        }
+    }
+}
+
+/// The command for the page viewer.
+#[derive(Debug, Clone, Copy, EnumString)]
+enum PageViewerCmd {
+    #[strum(serialize = "f")]
+    PreviousPage,
+    #[strum(serialize = "b")]
+    NextPage,
+    #[strum(serialize = "q")]
+    Quit,
+}
+
+// endregion
+
+// region: App Utility Functions
+
+/// Read a single line from stdin, trimmed of surrounding whitespace.
+fn read_line() -> Result<String> {
+    let mut line = String::new();
+    std::io::stdin().read_line(&mut line)?;
+    Ok(line.trim().to_string())
+}
+
+/// Get the unit string for a device kind.
+fn get_device_unit(device_kind: DeviceKind) -> &'static str {
+    match device_kind {
+        // YYC MARK: This is ohm char.
+        DeviceKind::Resistor => "\u{2126}",
+        DeviceKind::Capacitor => "F",
+        DeviceKind::Inductor => "H",
+    }
+}
+
+// endregion
+
+/// The app.
+pub struct App {
+    /// The resolver for the app.
+    resolver: Box<dyn Resolver>,
+}
+
+impl App {
+    /// Create a new app with the given configuration.
+    pub fn new(config: AppConfig) -> Result<Self> {
+        let sepcs = SpecCatalog::from_file(
+            config.get_resistor_spec(),
+            config.get_capacitor_specs(),
+            config.get_inductor_specs(),
+        )?;
+
+        let resolver: Box<dyn Resolver> = match config.get_resolver() {
+            AppResolver::Lut => Box::new(LutResolver::new(&sepcs)?),
+            AppResolver::Bfs => Box::new(BfsResolver::new(sepcs)),
+        };
+
+        Ok(Self { resolver })
+    }
+
+    /// Run the app.
+    pub fn run(&self) -> Result<()> {
+        println!("LCR Connector");
+        println!(r#"Type "help" for more info. Type "exit" to quit."#);
+        self.op_main()?;
+        Ok(())
+    }
+
+    // region: Subcommand Processors
+
+    fn op_main(&self) -> Result<()> {
+        loop {
+            match self.accept_command::<MainCmd>()? {
+                MainCmd::Query => self.op_query()?,
+                MainCmd::Help => {
+                    println!("LCR Connector Help:");
+                    println!();
+                    println!("query: do a query.");
+                    println!("help: show all command.");
+                    println!("exit: exit this app.");
+                }
+                MainCmd::Exit => break,
+            }
+        }
+        Ok(())
+    }
+
+    fn op_query(&self) -> Result<()> {
+        // collecting request infos
+        println!("What are you connecting?");
+        println!("r: resistor");
+        println!("l: inductor");
+        println!("c: capacitor");
+        let device_kind = self.accept_command::<QueryDeviceChoice>()?.to_device_kind();
+
+        println!("Your target value?");
+        println!(r#"Example: "2.1k", "0.75m", "3.2M" and etc."#);
+        let target_value = self.accept_device_value()?;
+
+        println!("Your tolerance?");
+        println!(r#"It can be absolute value like "2.1k"."#);
+        println!(r#"Or relative value to your target value like "19.5%"."#);
+        let tolerance = self.accept_device_value_tolerance(target_value)?;
+
+        println!("How to sort result?");
+        println!("a: more accuracy");
+        println!("l: less component");
+        let response_priority = self
+            .accept_command::<QuerySortPriority>()?
+            .to_response_priority();
+
+        println!("How may result are you expected?");
+        let count_limit = self.accept_count_value()?;
+
+        // build request and ask resolver
+        let request = Request::new(
+            device_kind,
+            target_value,
+            tolerance,
+            response_priority,
+            count_limit,
+        )?;
+        let response = self.resolver.resolve(&request)?;
+
+        // use page viewer to show result
+        self.op_page_viewer(&response)?;
+
+        Ok(())
+    }
+
+    fn op_page_viewer(&self, response: &Response) -> Result<()> {
+        let cnt = response.len();
+        if cnt == 0 {
+            println!("Sorry, no result!");
+            println!("Please consider adjusting your requirements and try again.");
+            return Ok(());
+        }
+
+        const ITEMS_PER_PAGE: usize = 10;
+        let all_page = cnt / ITEMS_PER_PAGE;
+        let mut current_page = 0usize;
+
+        loop {
+            // print list
+            for i in 0..ITEMS_PER_PAGE - 1 {
+                // build index and check it
+                let index = current_page * (ITEMS_PER_PAGE - 1) + i;
+                if index >= cnt {
+                    continue;
+                }
+                // and print it
+                self.illustrate_response(response, index)?;
+            }
+
+            // print page footer
+            println!();
+            println!("Page {} of {}.", current_page + 1, all_page + 1);
+            println!("f: previous page. b: next page. q: quit this viewer.");
+            // check command
+            match self.accept_command::<PageViewerCmd>()? {
+                PageViewerCmd::PreviousPage => current_page = current_page.saturating_sub(1),
+                PageViewerCmd::NextPage => current_page = all_page.min(current_page + 1),
+                PageViewerCmd::Quit => break,
+            }
+        }
+
+        Ok(())
+    }
+
+    // endregion
+
+    // region: Command Utilities
+
+    /// Accept a command from the user.
+    ///
+    /// Loops until a valid command is entered.
+    fn accept_command<T>(&self) -> Result<T>
+    where
+        T: FromStr,
+    {
+        loop {
+            self.show_prompt_arrow()?;
+            let words = read_line()?;
+            if words.is_empty() {
+                continue;
+            }
+
+            match words.parse::<T>() {
+                Ok(cmd) => return Ok(cmd),
+                Err(_) => println!("Unknown command, please try again."),
+            }
+        }
+    }
+
+    /// Accept a count value from the user.
+    fn accept_count_value(&self) -> Result<usize> {
+        loop {
+            self.show_prompt_arrow()?;
+            let words = read_line()?;
+            if words.is_empty() {
+                continue;
+            }
+
+            match words.parse::<usize>() {
+                Ok(value) => {
+                    if value > MAX_RESPONSE_CNT || value == 0 {
+                        println!("Wrong value, please try again.");
+                    } else {
+                        return Ok(value);
+                    }
+                }
+                Err(_) => {
+                    println!("Wrong value, please try again.");
+                }
+            }
+        }
+    }
+
+    /// Accept a device value from the user.
+    fn accept_device_value(&self) -> Result<f64> {
+        loop {
+            self.show_prompt_arrow()?;
+            let words = read_line()?;
+            if words.is_empty() {
+                continue;
+            }
+
+            let value = self.parse_human_readable_value(&words);
+            match value {
+                Some(v) => return Ok(v),
+                None => println!("Wrong value, please try again."),
+            }
+        }
+    }
+
+    /// Accept a tolerance value from the user.
+    ///
+    /// The tolerance can be an absolute value (like "2.1k") or a percentage
+    /// relative to the target value (like "19.5%").
+    fn accept_device_value_tolerance(&self, target_value: f64) -> Result<f64> {
+        loop {
+            self.show_prompt_arrow()?;
+            let words = read_line()?;
+            if words.is_empty() {
+                continue;
+            }
+
+            let value: Option<f64> = if let Some(pct_str) = words.strip_suffix('%') {
+                let value = self.parse_plain_float(pct_str, |x| *x >= 0.0 && *x <= 100.0);
+                value
+                    .map(|v| v / 100.0 * target_value)
+                    .map(|v| validate_device_value(v))
+                    .transpose()
+                    .ok()
+                    .flatten()
+            } else {
+                self.parse_human_readable_value(&words)
+            };
+
+            match value {
+                Some(v) => return Ok(v),
+                None => println!("Wrong value, please try again."),
+            }
+        }
+    }
+
+    fn show_prompt_arrow(&self) -> Result<()> {
+        print!("> ");
+        std::io::stdout().flush()?;
+        Ok(())
+    }
+
+    /// Parse a plain float value.
+    ///
+    /// # Arguments
+    ///
+    /// * `user_value` - The value to parse.
+    /// * `checker` - A function that checks if the input is valid.
+    ///   It takes a float as input and returns a bool. True means the input is valid,
+    ///   otherwise False.
+    ///
+    /// # Returns
+    ///
+    /// The parsed value if it is valid, otherwise `None`.
+    fn parse_plain_float(&self, user_value: &str, checker: impl Fn(&f64) -> bool) -> Option<f64> {
+        // try parsing it first then check it by checker
+        let value = match user_value.parse::<f64>() {
+            Ok(value) => value,
+            Err(_) => return None,
+        };
+        let value = validate_floating_point(value).ok()?;
+        if checker(&value) { Some(value) } else { None }
+    }
+
+    /// Parse a human-readable device value.
+    ///
+    /// # Arguments
+    ///
+    /// * `user_value` - The value to parse.
+    ///
+    /// # Returns
+    ///
+    /// The parsed value if it is valid and positive, otherwise `None`.
+    fn parse_human_readable_value(&self, user_value: &str) -> Option<f64> {
+        // parse it
+        let value = from_human_readable_value(user_value).ok()?;
+        // then check its range
+        if value > 0.0 { Some(value) } else { None }
+    }
+
+    // endregion
+
+    // region: Response Display Utilities
+
+    /// Format a device value for display in the circuit graph.
+    fn to_circuit_graph_value(&self, value: f64, device_kind: DeviceKind) -> String {
+        // Remove sign and append device unit
+        let hr = to_human_readable_value(value);
+        let without_sign = &hr[1..];
+        format!("{}{}", without_sign, get_device_unit(device_kind))
+    }
+
+    /// Format a device value for the plan header.
+    fn to_plan_head_value(&self, value: f64, device_kind: DeviceKind) -> String {
+        // Remove sign and append device unit
+        let hr = to_human_readable_value(value);
+        let without_sign = &hr[1..];
+        format!("{}{}", without_sign, get_device_unit(device_kind))
+    }
+
+    /// Format a difference value for the plan header.
+    fn to_plan_head_diff(&self, value: f64, device_kind: DeviceKind) -> String {
+        // Keep the sign and append device unit
+        format!(
+            "{}{}",
+            to_human_readable_value(value),
+            get_device_unit(device_kind)
+        )
+    }
+
+    /// Format a relative difference as percentage.
+    fn to_plan_head_diff_pct(&self, value: f64) -> String {
+        // Keep the sign and format it as percentage style without trailing device unit
+        format!("{:.2}%", value * 100.0)
+    }
+
+    // YYC MARK:
+    // The function showing circuit graph should be maintained carefully.
+    // First, we want they are show in console properly,
+    // And we also want they have good code view.
+    //
+    // I notices that the number part of the output of `to_human_readable_value` will only be
+    // "+999.9999" or "+9.9999e+00". So its maximum of its length is 11, considering the possibility,
+    // that the absolute value of exponential part is larger than 99, is close to zero.
+    // After putting the scale unit and device unit together like " nF",
+    // the whole maximum size of the built string is 14.
+    //
+    // So we need pick a larger number and odd number for the space for showing device value,
+    // because odd value can be divided by two so it can be split as two parts equally
+    // for the convenient alignment of some circuit graphs.
+    // My picked value is 16.
+    // So you will see that I use `:^16` for a center alignment to given string.
+    //
+    // After this, we also need set the padding value carefully.
+    // This value should consider the length of f-string syntax, pre-defined chars and required chars.
+    // To make sure a pretty showcase both in code and display.
+
+    /// Illustrate a response item.
+    fn illustrate_response(&self, response: &Response, index: usize) -> Result<()> {
+        let item = response.get(index).expect("unexpected invalid index");
+        let device_kind = response.device_kind();
+        // print header
+        println!(
+            "Plan {:<4} Value: {:<16} Diff: {} ({})",
+            index + 1,
+            self.to_plan_head_value(item.value(), device_kind),
+            self.to_plan_head_diff(item.difference(), device_kind),
+            self.to_plan_head_diff_pct(item.relative_difference()),
+        );
+        // print circuit graph
+        self.illustrate_circuit(item.circuit(), device_kind)?;
+        Ok(())
+    }
+
+    /// Illustrate a circuit based on its device scale.
+    fn illustrate_circuit(
+        &self,
+        circuit: &Circuit,
+        device_kind: DeviceKind,
+    ) -> Result<()> {
+        match circuit.device_scale() {
+            CircuitDeviceScale::One => {
+                self.illustrate_one_device_circuit(circuit, device_kind);
+            }
+            CircuitDeviceScale::Two => {
+                self.illustrate_two_device_circuit(circuit, device_kind)?;
+            }
+            CircuitDeviceScale::Three => {
+                self.illustrate_three_device_circuit(circuit, device_kind)?;
+            }
+        }
+        Ok(())
+    }
+
+    /// Illustrate a one-device circuit.
+    fn illustrate_one_device_circuit(&self, circuit: &Circuit, device_kind: DeviceKind) {
+        let dev1 = self.to_circuit_graph_value(circuit.first_device_value(), device_kind);
+        println!("──[{:^16}]──", dev1);
+    }
+
+    /// Illustrate a two-device circuit.
+    fn illustrate_two_device_circuit(
+        &self,
+        circuit: &Circuit,
+        device_kind: DeviceKind,
+    ) -> Result<()> {
+        let dev1 = self.to_circuit_graph_value(circuit.first_device_value(), device_kind);
+        let j2 = circuit.second_device_joint()?;
+        let dev2 = self.to_circuit_graph_value(circuit.second_device_value()?, device_kind);
+        match j2 {
+            JointKind::Series => {
+                println!("──[{:^16}]──[{:^16}]──", dev1, dev2);
+            }
+            JointKind::Parallel => {
+                let sep0 = " ".repeat(6 + (16 - 10));
+                println!("  ┌──[{:^16}]──┐  ", dev1);
+                println!("──┤   {}       ├──", sep0);
+                println!("  └──[{:^16}]──┘  ", dev2);
+            }
+        }
+        Ok(())
+    }
+
+    /// Illustrate a three-device circuit.
+    fn illustrate_three_device_circuit(
+        &self,
+        circuit: &Circuit,
+        device_kind: DeviceKind,
+    ) -> Result<()> {
+        let dev1 = self.to_circuit_graph_value(circuit.first_device_value(), device_kind);
+        let j2 = circuit.second_device_joint()?;
+        let dev2 = self.to_circuit_graph_value(circuit.second_device_value()?, device_kind);
+        let j3 = circuit.third_device_joint()?;
+        let dev3 = self.to_circuit_graph_value(circuit.third_device_value()?, device_kind);
+        match j2 {
+            JointKind::Series => match j3 {
+                JointKind::Series => {
+                    // All in series
+                    println!("──[{dev1:^16}]──[{dev2:^16}]──[{dev3:^16}]──");
+                }
+                JointKind::Parallel => {
+                    // First series then parallel
+                    let sep0 = "─".repeat(6 + ((16 - 10) / 2));
+                    let sep1 = " ".repeat(6 + 2 * (16 - 10));
+                    println!("  ┌──[{dev1:^16}]──[{dev2:^16}]──┐  ");
+                    println!("──┤   {sep1}                     ├──");
+                    println!("  └───{sep0}[{dev3:^16}]{sep0}───┘  ");
+                }
+            },
+            JointKind::Parallel => match j3 {
+                JointKind::Series => {
+                    // First parallel then series
+                    let sep0 = " ".repeat(6 + (16 - 10));
+                    println!("   {sep0}       ┌──[{dev1:^16}]──┐  ");
+                    println!("──[{dev3:^16}]──┤   {sep0}       ├──");
+                    println!("   {sep0}       └──[{dev2:^16}]──┘  ");
+                }
+                JointKind::Parallel => {
+                    // All in parallel
+                    println!("  ┌──[{dev1:^16}]──┐  ");
+                    println!("──┼──[{dev2:^16}]──┼──");
+                    println!("  └──[{dev3:^16}]──┘  ");
+                }
+            },
+        }
+        Ok(())
+    }
+
+    // endregion
+}

kernel/lcrconn-cli/src/cli.rs

@@ -0,0 +1,103 @@
+use std::path::{Path, PathBuf};
+
+use clap::{Parser, ValueEnum};
+
+/// The configuration for the app.
+pub struct AppConfig {
+    /// The resolver for the app.
+    resolver: AppResolver,
+    /// The path to the resistor specs file.
+    resistor_specs: PathBuf,
+    /// The path to the capacitor specs file.
+    capacitor_specs: PathBuf,
+    /// The path to the inductor specs file.
+    inductor_specs: PathBuf,
+}
+
+impl AppConfig {
+    /// Get the resolver.
+    pub fn get_resolver(&self) -> &AppResolver {
+        &self.resolver
+    }
+    /// Get the path to the resistor specs file.
+    pub fn get_resistor_spec(&self) -> &Path {
+        &self.resistor_specs
+    }
+    /// Get the path to the capacitor specs file.
+    pub fn get_capacitor_specs(&self) -> &Path {
+        &self.capacitor_specs
+    }
+    /// Get the path to the inductor specs file.
+    pub fn get_inductor_specs(&self) -> &Path {
+        &self.inductor_specs
+    }
+}
+
+/// The resolver for the app.
+#[derive(Debug, Clone, ValueEnum)]
+pub enum AppResolver {
+    /// The look-up table resolver.
+    #[value(name = "lut")]
+    Lut,
+    /// The BFS resolver.
+    #[value(name = "bfs")]
+    Bfs,
+}
+
+/// Get the resistor, capacitor, or inductor circuit which has the closest value
+/// for your given value within at most 3 devices.
+#[derive(Parser)]
+#[command(
+    name = "LCR Connector",
+    version,
+    about = "Get the resistor, capacitor, or inductor circuit which has the closest value for your given value within at most 3 devices."
+)]
+struct Cli {
+    /// The resolver you want to use.
+    #[arg(short = 's', long = "resolver", required = true, value_enum)]
+    resolver: AppResolver,
+
+    /// The path to the resistor specs file.
+    #[arg(
+        short = 'r',
+        long = "resistor",
+        required = true,
+        value_name = "RESISTOR.TXT"
+    )]
+    resistor_specs: PathBuf,
+
+    /// The path to the inductor specs file.
+    #[arg(
+        short = 'l',
+        long = "inductor",
+        required = true,
+        value_name = "INDUCTOR.TXT"
+    )]
+    inductor_specs: PathBuf,
+
+    /// The path to the capacitor specs file.
+    #[arg(
+        short = 'c',
+        long = "capacitor",
+        required = true,
+        value_name = "CAPACITOR.TXT"
+    )]
+    capacitor_specs: PathBuf,
+}
+
+impl From<Cli> for AppConfig {
+    fn from(args: Cli) -> Self {
+        Self {
+            resolver: args.resolver,
+            resistor_specs: args.resistor_specs,
+            capacitor_specs: args.capacitor_specs,
+            inductor_specs: args.inductor_specs,
+        }
+    }
+}
+
+pub fn parse_args() -> AppConfig {
+    let args = Cli::parse();
+    let config = AppConfig::from(args);
+    config
+}

kernel/lcrconn-cli/src/main.rs

@@ -0,0 +1,15 @@
+mod app;
+mod cli;
+
+fn main() {
+    let config = cli::parse_args();
+
+    let app = app::App::new(config).unwrap_or_else(|err| {
+        eprintln!("Fail to initialize application: {}", err);
+        std::process::exit(1);
+    });
+    app.run().unwrap_or_else(|err| {
+        eprintln!("Runtime error: {}", err);
+        std::process::exit(1);
+    });
+}

kernel/lcrconn/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "lcrconn"
+version = "1.0.0"
+edition = "2024"
+
+[dependencies]
+thiserror = "2.0.12"
+ordered-float = "=5.3.0"
+itertools = "0.15.0"
+strum = "=0.28.0"
+strum_macros = "=0.28.0"

kernel/lcrconn/src/common.rs

@@ -0,0 +1,392 @@
+use strum_macros::EnumIter;
+use thiserror::Error as TeError;
+
+// region: Validator
+
+/// Error occurs when validating floating point value.
+#[derive(Debug, TeError)]
+#[error("given floating point value {0} is invalid")]
+pub struct FloatingPointError(f64);
+
+/// Check whether given floating point value is okey for arithmetic operation.
+pub fn validate_floating_point(f: f64) -> Result<f64, FloatingPointError> {
+    if f.is_finite() {
+        Ok(f)
+    } else {
+        Err(FloatingPointError(f))
+    }
+}
+
+/// Error occurs when validating device value.
+#[derive(Debug, TeError)]
+pub enum DeviceValueError {
+    #[error("given device value is bad floating point: {0}")]
+    BadFloatingPoint(#[from] FloatingPointError),
+    #[error("given device value {0} is out of range")]
+    OutOfRange(f64),
+}
+
+/// Check whether given value is good for device value.
+///
+/// A good device value should be finity floating point,
+/// and it should be greater than zero.
+pub fn validate_device_value(f: f64) -> Result<f64, DeviceValueError> {
+    let f = validate_floating_point(f)?;
+    if f > 0f64 {
+        Ok(f)
+    } else {
+        Err(DeviceValueError::OutOfRange(f))
+    }
+}
+
+// endregion
+
+// region: Circuit Utilities
+
+/// The kind of device.
+#[derive(Debug, Clone, Copy)]
+pub enum DeviceKind {
+    /// Resistor device.
+    Resistor,
+    /// Capacitor device.
+    Capacitor,
+    /// Inductor device.
+    Inductor,
+}
+
+/// The joint type between 2 devices.
+#[derive(Debug, Clone, Copy, EnumIter)]
+pub enum JointKind {
+    /// Series connection.
+    Series,
+    /// Parallel connection.
+    Parallel,
+}
+
+impl JointKind {
+    /// Flip the joint kind from series to parallel or vice versa.
+    ///
+    /// # Returns
+    ///
+    /// The flipped joint kind.
+    pub fn flip(self) -> Self {
+        match self {
+            JointKind::Series => JointKind::Parallel,
+            JointKind::Parallel => JointKind::Series,
+        }
+    }
+}
+
+/// The scale of devices in the circuit.
+#[derive(Debug, Clone, Copy)]
+pub enum CircuitDeviceScale {
+    /// One device.
+    One,
+    /// Two devices.
+    Two,
+    /// Three devices.
+    Three,
+}
+
+impl CircuitDeviceScale {
+    /// Convert circuit device scale to device count.
+    /// The return value only can be 1, 2, and 3.
+    pub fn to_device_count(self) -> usize {
+        match self {
+            CircuitDeviceScale::One => 1,
+            CircuitDeviceScale::Two => 2,
+            CircuitDeviceScale::Three => 3,
+        }
+    }
+}
+
+// endregion
+
+// region: Circuit Stuff
+
+/// Error occurs when manipulating [Circuit] and [SubCircuit].
+#[derive(Debug, TeError)]
+pub enum CircuitError {
+    #[error("invalid device value in circuit: {0}")]
+    BadDeviceValue(DeviceValueError),
+    #[error("third device cannot exist without second device when building circuit")]
+    InterleavedSubCircuit,
+    #[error("the joint or device with given index is not presented in circuit")]
+    NoSuchDevice,
+
+    #[error("invalid target value: {0}")]
+    BadTargetValue(DeviceValueError),
+    #[error("invalid pre-evaluated circuit value: {0}")]
+    BadCircuitValue(DeviceValueError),
+    #[error("bad previous evaluated joint value: {0}")]
+    BadPreviousValue(DeviceValueError),
+    #[error("floating point is invalid after arithmetic operation: {0}")]
+    BadArithmetic(FloatingPointError),
+}
+
+/// The part of circuit composed of two devices and the joint kind.
+#[derive(Debug, Clone)]
+pub struct SubCircuit {
+    /// The value of the device.
+    device_value: f64,
+    /// The joint kind between this device and the next device.
+    joint_kind: JointKind,
+}
+
+impl SubCircuit {
+    /// Initialize subcircuit with given device value and joint kind.
+    ///
+    /// The input device value should greater than zero,
+    /// otherwise an error will return.
+    pub fn new(device_value: f64, joint_kind: JointKind) -> Result<Self, CircuitError> {
+        let device_value =
+            validate_device_value(device_value).map_err(|err| CircuitError::BadDeviceValue(err))?;
+        Ok(Self {
+            device_value,
+            joint_kind,
+        })
+    }
+
+    /// Evaluate the joint value with given previous joint evaluated value and device kind.
+    ///
+    /// Parameter `value` should be the value evaluated from previous joint.
+    /// And it should greater than zero.
+    /// `device_kind` is the kind of the device.
+    pub fn evaluate(&self, value: f64, device_kind: DeviceKind) -> Result<f64, CircuitError> {
+        // Check the range of provided value for computing
+        let value =
+            validate_device_value(value).map_err(|err| CircuitError::BadPreviousValue(err))?;
+
+        // We perform series connect for: series resistor, series inductor and parallel capacitor.
+        // We perform parallel connect for: parallel resistor, parallel inductor and series capacitor.
+        let joint_kind = match device_kind {
+            DeviceKind::Capacitor => self.joint_kind.flip(),
+            _ => self.joint_kind,
+        };
+
+        validate_floating_point(match joint_kind {
+            JointKind::Series => self.device_value + value,
+            JointKind::Parallel => (self.device_value * value) / (self.device_value + value),
+        })
+        .map_err(|err| CircuitError::BadArithmetic(err))
+    }
+
+    /// Get the device value.
+    pub fn device_value(&self) -> f64 {
+        self.device_value
+    }
+
+    /// Get the joint kind.
+    pub fn joint_kind(&self) -> JointKind {
+        self.joint_kind
+    }
+}
+
+/// The circuit composed of multiple joints.
+#[derive(Clone, Debug)]
+pub struct Circuit {
+    /// The value of the first device.
+    first_device_value: f64,
+    /// The second device and its joint property.
+    second_device_subckt: Option<SubCircuit>,
+    /// The third device and its joint property.
+    third_device_subckt: Option<SubCircuit>,
+}
+
+impl Circuit {
+    /// Initialize the circuit with subcircuit.
+    ///
+    /// - `first_device_value`: The value of the first device.
+    /// - `second_device_subckt`: The second device and its joint property.
+    /// - `third_device_subckt`: The third device and its joint property.
+    fn new(
+        first_device_value: f64,
+        second_device_subckt: Option<SubCircuit>,
+        third_device_subckt: Option<SubCircuit>,
+    ) -> Result<Self, CircuitError> {
+        // Check the value of first device
+        let first_device_value = validate_device_value(first_device_value)
+            .map_err(|err| CircuitError::BadDeviceValue(err))?;
+        // Check impossible form
+        if second_device_subckt.is_none() && third_device_subckt.is_some() {
+            return Err(CircuitError::InterleavedSubCircuit);
+        }
+
+        // Everything is okey
+        Ok(Self {
+            first_device_value,
+            second_device_subckt,
+            third_device_subckt,
+        })
+    }
+
+    /// Create a circuit from a single device.
+    pub fn from_one_device(device1_value: f64) -> Result<Self, CircuitError> {
+        Self::new(device1_value, None, None)
+    }
+
+    /// Create a circuit from two devices.
+    pub fn from_two_devices(
+        device1_value: f64,
+        device2_value: f64,
+        device2_joint: JointKind,
+    ) -> Result<Self, CircuitError> {
+        Self::new(
+            device1_value,
+            Some(SubCircuit::new(device2_value, device2_joint)?),
+            None,
+        )
+    }
+
+    /// Create a circuit from three devices.
+    pub fn from_three_devices(
+        device1_value: f64,
+        device2_value: f64,
+        device2_joint: JointKind,
+        device3_value: f64,
+        device3_joint: JointKind,
+    ) -> Result<Self, CircuitError> {
+        Self::new(
+            device1_value,
+            Some(SubCircuit::new(device2_value, device2_joint)?),
+            Some(SubCircuit::new(device3_value, device3_joint)?),
+        )
+    }
+
+    /// Evaluate the circuit value with device kind
+    pub fn evaluate(&self, device_kind: DeviceKind) -> Result<f64, CircuitError> {
+        let mut value = self.first_device_value;
+
+        match &self.second_device_subckt {
+            Some(subckt) => value = subckt.evaluate(value, device_kind)?,
+            None => return Ok(value),
+        }
+
+        match &self.third_device_subckt {
+            Some(subckt) => value = subckt.evaluate(value, device_kind)?,
+            None => return Ok(value),
+        }
+
+        Ok(value)
+    }
+
+    /// Get the device scale.
+    ///
+    /// # Returns
+    ///
+    /// The device scale.
+    pub fn device_scale(&self) -> CircuitDeviceScale {
+        if self.third_device_subckt.is_some() {
+            CircuitDeviceScale::Three
+        } else if self.second_device_subckt.is_some() {
+            CircuitDeviceScale::Two
+        } else {
+            CircuitDeviceScale::One
+        }
+    }
+
+    /// Get the value of the first device.
+    pub fn first_device_value(&self) -> f64 {
+        self.first_device_value
+    }
+
+    /// Get the joint kind of the second device.
+    pub fn second_device_joint(&self) -> Result<JointKind, CircuitError> {
+        self.second_device_subckt
+            .as_ref()
+            .map(|s| s.joint_kind())
+            .ok_or(CircuitError::NoSuchDevice)
+    }
+
+    /// Get the value of the second device.
+    pub fn second_device_value(&self) -> Result<f64, CircuitError> {
+        self.second_device_subckt
+            .as_ref()
+            .map(|s| s.device_value())
+            .ok_or(CircuitError::NoSuchDevice)
+    }
+
+    /// Get the joint kind of the third device.
+    pub fn third_device_joint(&self) -> Result<JointKind, CircuitError> {
+        self.third_device_subckt
+            .as_ref()
+            .map(|s| s.joint_kind())
+            .ok_or(CircuitError::NoSuchDevice)
+    }
+
+    /// Get the value of the third device.
+    pub fn third_device_value(&self) -> Result<f64, CircuitError> {
+        self.third_device_subckt
+            .as_ref()
+            .map(|s| s.device_value())
+            .ok_or(CircuitError::NoSuchDevice)
+    }
+}
+
+/// The evaluation result of circuit with target value.
+#[derive(Debug, Clone)]
+pub struct CircuitEvaluation {
+    /// The value of this circuit.
+    pub value: f64,
+    /// The signed difference between the target value and the value of this circuit.
+    ///
+    /// Positive value indicates that the value of this circuit is greater than the target value.
+    /// Negative value indicates that the value of this circuit is less than the target value.
+    pub difference: f64,
+    /// The unsigned difference between the target value and the value of this circuit.
+    pub unsigned_difference: f64,
+    /// The signed relative difference between the target value and the value of this circuit.
+    ///
+    /// Positive value indicates that the value of this circuit is greater than the target value.
+    /// Negative value indicates that the value of this circuit is less than the target value.
+    pub relative_difference: f64,
+    /// The unsigned relative difference between the target value and the value of this circuit.
+    pub unsigned_relative_difference: f64,
+}
+
+impl CircuitEvaluation {
+    /// Internal used constructor. Passed circuit `value` must be checked before calling this.
+    fn new(value: f64, target_value: f64) -> Result<Self, CircuitError> {
+        // Check target value
+        let target_value =
+            validate_device_value(target_value).map_err(|err| CircuitError::BadTargetValue(err))?;
+        // Start evaluating
+        let difference = validate_floating_point(value - target_value)
+            .map_err(|err| CircuitError::BadArithmetic(err))?;
+        let unsigned_difference = validate_floating_point(difference.abs())
+            .map_err(|err| CircuitError::BadArithmetic(err))?;
+        let relative_difference = validate_floating_point(difference / target_value)
+            .map_err(|err| CircuitError::BadArithmetic(err))?;
+        let unsigned_relative_difference = validate_floating_point(relative_difference.abs())
+            .map_err(|err| CircuitError::BadArithmetic(err))?;
+        // Return evaluation result
+        Ok(CircuitEvaluation {
+            value,
+            difference,
+            unsigned_difference,
+            relative_difference,
+            unsigned_relative_difference,
+        })
+    }
+
+    /// Evaluate circuit with device kind and target value.
+    pub fn from_circuit(
+        circuit: &Circuit,
+        device_kind: DeviceKind,
+        target_value: f64,
+    ) -> Result<Self, CircuitError> {
+        // Fetch circuit value and evaluate it.
+        let value = circuit.evaluate(device_kind)?;
+        Self::new(value, target_value)
+    }
+
+    /// Evaluate circuit with pre-evaluated circuit value and target value.
+    pub fn from_circuit_value(value: f64, target_value: f64) -> Result<Self, CircuitError> {
+        // Check user given circuit value and evaluate it.
+        let value =
+            validate_device_value(value).map_err(|err| CircuitError::BadCircuitValue(err))?;
+        Self::new(value, target_value)
+    }
+}
+
+// endregion

kernel/lcrconn/src/lib.rs

@@ -0,0 +1,8 @@
+pub mod common;
+pub mod spec;
+pub mod query;
+pub mod resolver;
+
+pub use common::DeviceKind;
+pub use query::{Request, Response, ResponsePriority};
+pub use resolver::{Resolver, BfsResolver, LutResolver};

kernel/lcrconn/src/query.rs

@@ -0,0 +1,262 @@
+use crate::common::{
+    Circuit, CircuitError, CircuitEvaluation, DeviceKind, DeviceValueError, validate_device_value,
+};
+use ordered_float::OrderedFloat;
+use thiserror::Error as TeError;
+
+/// The priority of the result.
+#[derive(Debug, Clone, Copy)]
+pub enum ResponsePriority {
+    /// Less devices is the first priority.
+    LessDevices,
+    /// More accuracy is the first priority.
+    MoreAccuracy,
+}
+
+/// The maximum count for the response item count passed in request.
+pub const MAX_RESPONSE_CNT: usize = 50;
+
+/// The error occurs when building [Request].
+#[derive(Debug, TeError)]
+pub enum RequestError {
+    #[error("invalid target value in request: {0}")]
+    BadTargetValue(DeviceValueError),
+    #[error("invalid tolerance in request: {0}")]
+    BadTolerance(DeviceValueError),
+    #[error("invalid response count {0} limit in request")]
+    BadCountLimit(usize),
+}
+
+/// All request information for the resolver.
+#[derive(Clone, Debug)]
+pub struct Request {
+    /// The kind of device to resolve.
+    device_kind: DeviceKind,
+    /// The target value of the device.
+    target_value: f64,
+    /// The tolerance of the device in absolute value.
+    tolerance: f64,
+    /// The priority principle when sorting response items.
+    response_priority: ResponsePriority,
+    /// The limited count of results.
+    count_limit: usize,
+}
+
+impl Request {
+    /// Create a new request with validation.
+    pub fn new(
+        device_kind: DeviceKind,
+        target_value: f64,
+        tolerance: f64,
+        response_priority: ResponsePriority,
+        count_limit: usize,
+    ) -> Result<Self, RequestError> {
+        // Check arguments
+        let target_value =
+            validate_device_value(target_value).map_err(|err| RequestError::BadTargetValue(err))?;
+        let tolerance =
+            validate_device_value(tolerance).map_err(|err| RequestError::BadTolerance(err))?;
+        if count_limit == 0 || count_limit > MAX_RESPONSE_CNT {
+            return Err(RequestError::BadCountLimit(count_limit));
+        }
+        // Everything is okey.
+        Ok(Self {
+            device_kind,
+            target_value,
+            tolerance,
+            response_priority,
+            count_limit,
+        })
+    }
+
+    /// Get the kind of device of this request.
+    pub fn get_device_kind(&self) -> DeviceKind {
+        self.device_kind
+    }
+
+    /// Get the target value of this request.
+    ///
+    /// The return value was ensured that it must be valid device value.
+    pub fn get_target_value(&self) -> f64 {
+        self.target_value
+    }
+
+    /// Get the tolerance of this request.
+    ///
+    /// The return value was ensured that it must be unsigned non-relative valid device value.
+    pub fn get_tolerance(&self) -> f64 {
+        self.tolerance
+    }
+
+    /// Get the priority principle when sorting response items.
+    pub fn get_response_priority(&self) -> ResponsePriority {
+        self.response_priority
+    }
+
+    /// Get the limited count of results.
+    ///
+    /// The return value was ensured that it must >= 0 and < [`MAX_RESPONSE_CNT`].
+    pub fn get_count_limit(&self) -> usize {
+        self.count_limit
+    }
+}
+
+/// Error occurs when building [Response] and [ResponseItem].
+#[derive(Debug, TeError)]
+pub enum ResponseError {
+    #[error("failed on evaluating circuit: {0}")]
+    EvaluateCircuit(#[from] CircuitError),
+}
+
+/// The possible solution given by the resolver.
+#[derive(Clone, Debug)]
+pub struct ResponseItem {
+    /// The circuit of this response item.
+    circuit: Circuit,
+    /// The evaluation result of this circuit.
+    circuit_evaluation: CircuitEvaluation,
+}
+
+impl ResponseItem {
+    /// Create a new response item by computing all values eagerly.
+    fn new(circuit: Circuit, request: &Request) -> Result<Self, ResponseError> {
+        // YYC MARK:
+        // I can use OnceLock to implement the behavior closing to Python cached_property.
+        // But I didn't do that due to the increased size of this struct, and inviable error handling.
+        // So I decide to calculate all values in there.
+        let circuit_evaluation = CircuitEvaluation::from_circuit(
+            &circuit,
+            request.get_device_kind(),
+            request.get_target_value(),
+        )?;
+        // Build self and return
+        Ok(Self {
+            circuit,
+            circuit_evaluation,
+        })
+    }
+
+    /// The circuit of this response item.
+    pub fn circuit(&self) -> &Circuit {
+        &self.circuit
+    }
+
+    /// The device count of this circuit.
+    pub fn device_count(&self) -> usize {
+        self.circuit.device_scale().to_device_count()
+    }
+
+    /// The value of this circuit.
+    pub fn value(&self) -> f64 {
+        self.circuit_evaluation.value
+    }
+
+    /// The signed difference between the target value and the value of this circuit.
+    ///
+    /// Positive value indicates that the value of this circuit is greater than the target value.
+    /// Negative value indicates that the value of this circuit is less than the target value.
+    pub fn difference(&self) -> f64 {
+        self.circuit_evaluation.difference
+    }
+
+    /// The unsigned difference between the target value and the value of this circuit.
+    pub fn unsigned_difference(&self) -> f64 {
+        self.circuit_evaluation.unsigned_difference
+    }
+
+    /// The signed relative difference between the target value and the value of this circuit.
+    ///
+    /// Positive value indicates that the value of this circuit is greater than the target value.
+    /// Negative value indicates that the value of this circuit is less than the target value.
+    pub fn relative_difference(&self) -> f64 {
+        self.circuit_evaluation.relative_difference
+    }
+
+    /// The unsigned relative difference between the target value and the value of this circuit.
+    pub fn unsigned_relative_difference(&self) -> f64 {
+        self.circuit_evaluation.unsigned_relative_difference
+    }
+}
+
+/// The collection of possible solutions given by the resolver.
+///
+/// For getting the response items, please use `response[index]` or `response.get(index)`.
+/// For iterating the response items, please use the `into_iter()` method.
+/// For getting the count of response items, please use the `len()` method.
+pub struct Response {
+    /// The kind of device of this response.
+    device_kind: DeviceKind,
+    /// The sorted items by priority and difference.
+    sorted_items: Vec<ResponseItem>,
+}
+
+impl Response {
+    /// Create a new response from request and candidate circuits.
+    ///
+    /// The candidates are sorted by the priority specified in the request and then truncated
+    /// to the count limit.
+    ///
+    /// # Errors
+    ///
+    /// See [`ResponseItem::new`].
+    pub fn new<I>(request: &Request, candidates: I) -> Result<Self, ResponseError>
+    where
+        I: Iterator<Item = Circuit>,
+    {
+        let mut items: Vec<ResponseItem> = candidates
+            .into_iter()
+            .map(|c| ResponseItem::new(c, request))
+            .collect::<Result<_, _>>()?;
+
+        // Sort by different strategy
+        match request.response_priority {
+            ResponsePriority::LessDevices => {
+                items.sort_by(|a, b| {
+                    a.device_count().cmp(&b.device_count()).then_with(|| {
+                        OrderedFloat(a.unsigned_difference())
+                            .cmp(&OrderedFloat(b.unsigned_difference()))
+                    })
+                });
+            }
+            ResponsePriority::MoreAccuracy => {
+                items.sort_by(|a, b| {
+                    OrderedFloat(a.unsigned_difference())
+                        .cmp(&OrderedFloat(b.unsigned_difference()))
+                });
+            }
+        }
+
+        // Cut item by limit
+        items.truncate(request.count_limit);
+
+        Ok(Self {
+            device_kind: request.device_kind,
+            sorted_items: items,
+        })
+    }
+
+    /// The kind of device of this response.
+    pub fn device_kind(&self) -> DeviceKind {
+        self.device_kind
+    }
+
+    /// The number of response items.
+    pub fn len(&self) -> usize {
+        self.sorted_items.len()
+    }
+
+    /// Whether the response is empty.
+    pub fn is_empty(&self) -> bool {
+        self.sorted_items.is_empty()
+    }
+
+    /// Get a response item by index.
+    pub fn get(&self, index: usize) -> Option<&ResponseItem> {
+        self.sorted_items.get(index)
+    }
+
+    /// Iterate over response items by reference.
+    pub fn iter(&self) -> impl Iterator<Item = &ResponseItem> {
+        self.sorted_items.iter()
+    }
+}

kernel/lcrconn/src/resolver.rs

@@ -0,0 +1,26 @@
+pub mod bfs;
+pub mod lut;
+
+use crate::query::{Request, Response};
+use thiserror::Error as TeError;
+
+/// Aggregated error occurs in every resolvers.
+#[derive(Debug, TeError)]
+pub enum ResolverError {
+    #[error("{0}")]
+    BfsResolver(#[from] bfs::BfsResolverError),
+    #[error("{0}")]
+    LutResolver(#[from] lut::LutResolverError),
+}
+
+/// Abstract base trait for all resolvers.
+pub trait Resolver {
+    /// Resolve the request and return the response.
+    ///
+    /// `request` is the request to resolve.
+    /// The response containing the best matching circuits.
+    fn resolve(&self, request: &Request) -> Result<Response, ResolverError>;
+}
+
+pub use bfs::BfsResolver;
+pub use lut::LutResolver;

kernel/lcrconn/src/resolver/bfs.rs

@@ -0,0 +1,370 @@
+use super::{Resolver, ResolverError};
+use crate::common::{Circuit, CircuitError, CircuitEvaluation, DeviceKind, JointKind};
+use crate::query::{Request, Response, ResponseError};
+use crate::spec::{SpecCatalog, SpecGroup};
+use itertools::Itertools;
+use ordered_float::OrderedFloat;
+use std::cmp::Ordering;
+use std::collections::BinaryHeap;
+use strum::IntoEnumIterator;
+use thiserror::Error as TeError;
+
+// region: BFS Resolver Kernel
+
+/// Error occurs BFS resolver.
+#[derive(Debug, TeError)]
+pub enum BfsResolverError {
+    #[error("failed on evaluating circuit: {0}")]
+    EvaluateCircuit(#[from] CircuitError),
+    #[error("fail to build response: {0}")]
+    Response(#[from] ResponseError),
+}
+
+// region: BFS Item
+
+/// The entry used in BFS iteration storing circuit and value.
+pub struct BfsItem {
+    /// The circuit represented by this item.
+    circuit: Circuit,
+    /// The evaluated value of the circuit.
+    value: f64,
+    /// The unsigned difference between the target value and the value of this circuit.
+    unsigned_difference: f64,
+}
+
+impl BfsItem {
+    /// Create a new BFS item by computing values eagerly.
+    pub fn new(circuit: Circuit, request: &Request) -> Result<Self, BfsResolverError> {
+        // YYC MARK:
+        // The same reason for replacing cached_property like I done in `ResponseItem`.
+        let eval = CircuitEvaluation::from_circuit(
+            &circuit,
+            request.get_device_kind(),
+            request.get_target_value(),
+        )?;
+
+        Ok(Self {
+            circuit,
+            value: eval.value,
+            unsigned_difference: eval.unsigned_difference,
+        })
+    }
+
+    /// The circuit represented by this item.
+    pub fn circuit(&self) -> &Circuit {
+        &self.circuit
+    }
+
+    /// The evaluated value of the circuit.
+    pub fn value(&self) -> f64 {
+        self.value
+    }
+
+    /// The unsigned difference between the target value and the value of this circuit.
+    pub fn unsigned_difference(&self) -> f64 {
+        self.unsigned_difference
+    }
+
+    /// Consume this item and return the inner circuit.
+    pub fn into_circuit(self) -> Circuit {
+        self.circuit
+    }
+}
+
+// endregion
+
+// region: BFS Resolver
+
+/// A resolver that uses breadth first search to find the best matching circuits.
+pub struct BfsResolver {
+    /// The specs for all device kinds.
+    specs: SpecCatalog,
+}
+
+impl BfsResolver {
+    // YYC MARK:
+    // Some circuit are equivalent in topology.
+    // If we deduplicate these equaivalent circuit in building result, there are too complex works.
+    // So we should deduplicated these equivalent circuit at the beginning, i.e. when generating them.
+    // So following iterator functions are taking this job.
+    //
+    // Additionally, these device values are coming from `spec`.
+    // All values are verified so the building step must success.
+    // So we can safely unwrap them.
+
+    /// Iterate all possible circuits with one device without repeating equivalent topology.
+    pub fn iter_one_device_circuit(specs: &SpecGroup) -> impl Iterator<Item = Circuit> {
+        // Every single device is unique so we directly output them.
+        // This feature is insured by spec itself.
+        specs
+            .iter()
+            .map(|v1| Circuit::from_one_device(v1).expect("unexpected failure on building circuit"))
+    }
+
+    /// Iterate all possible circuits with two devices without repeating equivalent topology.
+    pub fn iter_two_devices_circuit(specs: &SpecGroup) -> impl Iterator<Item = Circuit> {
+        // The two devices in this circuit is always swapable,
+        // so we iterate them without repeating.
+        itertools::iproduct!(
+            specs.iter().array_combinations_with_replacement::<2>(),
+            JointKind::iter()
+        )
+        .map(|([v1, v2], j2)| {
+            Circuit::from_two_devices(v1, v2, j2).expect("unexpected failure on building circuit")
+        })
+    }
+
+    /// Iterate all possible circuits with three devices without repeating equivalent topology.
+    pub fn iter_three_devices_circuit(specs: &SpecGroup) -> impl Iterator<Item = Circuit> {
+        // For generating three devices circuit,
+        // it should be consisted by 2 parts.
+        itertools::chain!(
+            // First, the whole circuit has only one joint type.
+            // In this case, 3 devices are swapable and we should iterate them without repeating
+            itertools::iproduct!(
+                specs.iter().array_combinations_with_replacement::<3>(),
+                JointKind::iter()
+            )
+            .map(
+                |([v1, v2, v3], j)| Circuit::from_three_devices(v1, v2, j, v3, j)
+                    .expect("unexpected failure on building circuit")
+            ),
+            // Second, if the joint type is different, then the first 2 devices are swapable.
+            // So we need iterate them without repeating.
+            itertools::iproduct!(
+                specs.iter().array_combinations_with_replacement::<2>(),
+                specs.iter(),
+                JointKind::iter()
+            )
+            .map(|([v1, v2], v3, j)| Circuit::from_three_devices(
+                v1,
+                v2,
+                j,
+                v3,
+                j.flip()
+            )
+            .expect("unexpected failure on building circuit")),
+        )
+    }
+}
+
+impl BfsResolver {
+    /// Create a new BFS resolver with the given specs.
+    pub fn new(specs: SpecCatalog) -> Self {
+        Self { specs }
+    }
+
+    fn pick_specs(&self, device_kind: DeviceKind) -> &SpecGroup {
+        match device_kind {
+            DeviceKind::Resistor => self.specs.resistor_specs(),
+            DeviceKind::Capacitor => self.specs.capacitor_specs(),
+            DeviceKind::Inductor => self.specs.inductor_specs(),
+        }
+    }
+
+    fn bfs_iteration(
+        specs: &SpecGroup,
+        request: &Request,
+    ) -> impl Iterator<Item = Result<BfsItem, BfsResolverError>> {
+        itertools::chain!(
+            BfsResolver::iter_one_device_circuit(&specs),
+            BfsResolver::iter_two_devices_circuit(&specs),
+            BfsResolver::iter_three_devices_circuit(&specs)
+        )
+        .map(|circuit| BfsItem::new(circuit, request))
+    }
+
+    fn intern_resolve(&self, request: &Request) -> Result<Response, BfsResolverError> {
+        // Pick specs group from catalog
+        let specs = self.pick_specs(request.get_device_kind());
+
+        // Create the result bucket.
+        // The count limit held by request is must be greater than zero, so we can simply unwrap it.
+        let mut bucket =
+            ResultBucket::new(request.get_count_limit()).expect("unexpected blank result bucket");
+
+        // Iterate circuit item one by one
+        for item in BfsResolver::bfs_iteration(specs, request) {
+            let item = item?;
+            // If circuit absolute difference is out of tolerance, skip it directly.
+            if item.unsigned_difference() <= request.get_tolerance() {
+                // Put it into bucket
+                let score = item.unsigned_difference();
+                bucket.insert(item, score);
+            } else {
+                continue;
+            }
+        }
+
+        // Return result
+        let circuits = bucket.into_iter().map(|i| i.into_circuit());
+        Ok(Response::new(request, circuits)?)
+    }
+}
+
+impl Resolver for BfsResolver {
+    fn resolve(&self, request: &Request) -> Result<Response, ResolverError> {
+        Ok(self.intern_resolve(request)?)
+    }
+}
+
+// endregion
+
+// endregion
+
+// region: Result Bucket Helper
+
+/// The error occurs in [`ResultBucket`] and [`ResultBucketItem`].
+#[derive(Debug, TeError)]
+enum ResultBucketError {
+    #[error("the size of binary heap {0} is invalid")]
+    BadBinHeapSize(usize),
+}
+
+// region: Result Bucket Item
+
+/// An item stored in a [`ResultBucket`].
+struct ResultBucketItem {
+    /// The score associated with this item.
+    score: OrderedFloat<f64>,
+    /// The underlying [BfsItem].
+    item: BfsItem,
+    /// Monotonic counter used as a tiebreaker when scores are equal,
+    /// ensuring that BinaryHeap never compares [BfsItem] directly.
+    seq: usize,
+}
+
+impl ResultBucketItem {
+    pub fn new(score: f64, item: BfsItem, seq: usize) -> Self {
+        Self {
+            score: OrderedFloat(score),
+            item,
+            seq,
+        }
+    }
+
+    pub fn get_score(&self) -> f64 {
+        self.score.0
+    }
+
+    pub fn into_bfs_item(self) -> BfsItem {
+        self.item
+    }
+}
+
+impl PartialEq for ResultBucketItem {
+    fn eq(&self, other: &Self) -> bool {
+        self.score.eq(&other.score) && self.seq.eq(&other.seq)
+    }
+}
+
+impl Eq for ResultBucketItem {}
+
+impl PartialOrd for ResultBucketItem {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for ResultBucketItem {
+    fn cmp(&self, other: &Self) -> Ordering {
+        // BinaryHeap is a max-heap: the greatest element is at the top.
+        // We want the entry with the largest score at the top.
+        self.score
+            .cmp(&other.score)
+            .then_with(|| self.seq.cmp(&other.seq))
+    }
+}
+
+// endregion
+
+// region: Result Bucket
+
+/// A bounded bucket that keeps up to N entries with the smallest scores.
+///
+/// When the bucket is full, inserting a new item only succeeds if its score
+/// is less than the current maximum; the maximum is then evicted.
+struct ResultBucket {
+    /// Maximum number of items the bucket can hold.
+    n: usize,
+    /// Max-heap of [`ResultBucketItem`].
+    /// The entry with the largest score sits at index 0.
+    heap: BinaryHeap<ResultBucketItem>,
+    /// Monotonic counter fed to each [`ResultBucketItem`] as a tiebreaker,
+    /// preventing BinaryHeap from comparing BfsItem on score collisions.
+    counter: usize,
+}
+
+impl ResultBucket {
+    /// Create a new bucket that holds at most `n` items.
+    pub fn new(n: usize) -> Result<Self, ResultBucketError> {
+        // Check heap size
+        if n == 0 {
+            Err(ResultBucketError::BadBinHeapSize(n))
+        } else {
+            Ok(Self {
+                n,
+                heap: BinaryHeap::new(),
+                counter: 0,
+            })
+        }
+    }
+    
+    // YYC MARK:
+    // I want to preserve these 2 functions so I add `allow(dead_code)` to them.
+
+    /// The number of items currently in the bucket.
+    #[allow(dead_code)]
+    pub fn len(&self) -> usize {
+        self.heap.len()
+    }
+
+    /// Whether the bucket is empty.
+    #[allow(dead_code)]
+    pub fn is_empty(&self) -> bool {
+        self.heap.is_empty()
+    }
+
+    /// Consume the bucket and return all stored items.
+    pub fn into_iter(self) -> impl Iterator<Item = BfsItem> {
+        self.heap.into_iter().map(|entry| entry.into_bfs_item())
+    }
+
+    /// Insert a [`BfsItem`] with the given score.
+    ///
+    /// If the bucket is not yet full the item is always inserted.
+    /// Otherwise the item is only inserted when `score` is smaller
+    /// than the largest score currently in the bucket; the entry
+    /// with the largest score is then evicted.
+    ///
+    /// Returns `true` if the item was inserted, `false` otherwise.
+    pub fn insert(&mut self, item: BfsItem, score: f64) -> bool {
+        // YYC MARK:
+        // Because this struct stored `n` is must greater than zero,
+        // so after the first `if` branch, the length of this binary heap must be greater than zero.
+        // So there must be at least one item in binary heap.
+        // and we can safely use `expect()` to peek from binary heap.
+        let entry = ResultBucketItem::new(score, item, self.counter);
+        if self.heap.len() < self.n {
+            self.heap.push(entry);
+            self.counter += 1;
+            true
+        } else if score
+            >= self
+                .heap
+                .peek()
+                .expect("unexpected blank binary heap")
+                .get_score()
+        {
+            false
+        } else {
+            *self.heap.peek_mut().expect("unexpected blank binary heap") = entry;
+            self.counter += 1;
+            true
+        }
+    }
+}
+
+// endregion
+
+// endregion

kernel/lcrconn/src/resolver/lut.rs

@@ -0,0 +1,251 @@
+use super::bfs::BfsResolver;
+use super::{Resolver, ResolverError};
+use crate::common::{Circuit, CircuitError, CircuitEvaluation, DeviceKind};
+use crate::spec::{SpecGroup, SpecCatalog};
+use crate::query::{Request, Response, ResponseError};
+use ordered_float::OrderedFloat;
+use thiserror::Error as TeError;
+
+// region: LUT Resolver Kernel
+
+/// Errors occurs in LUT resolver.
+#[derive(Debug, TeError)]
+pub enum LutResolverError {
+    #[error("failed on evaluating circuit: {0}")]
+    CircuitCalculator(#[from] CircuitError),
+    #[error("fail to build response: {0}")]
+    Response(#[from] ResponseError),
+}
+
+// region: LUT Item
+
+/// An item in the lookup table.
+pub struct LutItem {
+    /// The circuit represented by this item.
+    circuit: Circuit,
+    /// The value of this circuit.
+    value: OrderedFloat<f64>,
+}
+
+impl LutItem {
+    /// Create a new LUT item by computing the circuit value.
+    pub fn new(circuit: Circuit, device_kind: DeviceKind) -> Result<Self, LutResolverError> {
+        let value = circuit.evaluate(device_kind)?;
+        Ok(Self {
+            circuit,
+            value: OrderedFloat(value),
+        })
+    }
+
+    /// The circuit represented by this item.
+    pub fn circuit(&self) -> &Circuit {
+        &self.circuit
+    }
+
+    /// The value of this circuit.
+    pub fn value(&self) -> f64 {
+        self.value.0
+    }
+}
+
+// endregion
+
+// region: LUT Resolver
+
+/// A resolver that uses a lookup table to find the best matching circuit.
+pub struct LutResolver {
+    /// The lookup table for resistors.
+    resistor_lut: Vec<LutItem>,
+    /// The lookup table for capacitors.
+    capacitor_lut: Vec<LutItem>,
+    /// The lookup table for inductors.
+    inductor_lut: Vec<LutItem>,
+}
+
+impl LutResolver {
+    /// Create a new LUT resolver by building lookup tables from the given specs.
+    pub fn new(specs: &SpecCatalog) -> Result<Self, LutResolverError> {
+        Ok(Self {
+            resistor_lut: Self::build_lut(specs.resistor_specs(), DeviceKind::Resistor)?,
+            capacitor_lut: Self::build_lut(specs.capacitor_specs(), DeviceKind::Capacitor)?,
+            inductor_lut: Self::build_lut(specs.inductor_specs(), DeviceKind::Inductor)?,
+        })
+    }
+
+    fn build_lut(
+        specs: &SpecGroup,
+        device_kind: DeviceKind,
+    ) -> Result<Vec<LutItem>, LutResolverError> {
+        // Fetch all items
+        let mut lut = itertools::chain!(
+            BfsResolver::iter_one_device_circuit(&specs),
+            BfsResolver::iter_two_devices_circuit(&specs),
+            BfsResolver::iter_three_devices_circuit(&specs)
+        )
+        .map(|circuit| -> Result<LutItem, LutResolverError> { LutItem::new(circuit, device_kind) })
+        .collect::<Result<Vec<_>, _>>()?;
+        // Sort them and return
+        lut.sort_by(|a, b| a.value.cmp(&b.value));
+        Ok(lut)
+    }
+
+    fn pick_lut(&self, device_kind: DeviceKind) -> &[LutItem] {
+        match device_kind {
+            DeviceKind::Resistor => &self.resistor_lut,
+            DeviceKind::Capacitor => &self.capacitor_lut,
+            DeviceKind::Inductor => &self.inductor_lut,
+        }
+    }
+
+    fn intern_resolve(&self, request: &Request) -> Result<Response, LutResolverError> {
+        let lut = self.pick_lut(request.get_device_kind());
+        let target_value = request.get_target_value();
+        let count_limit = request.get_count_limit();
+        let mut bucket: Vec<Circuit> = Vec::new();
+
+        // Locate the insertion point of target in the sorted LUT.
+        // left/right start at the two nearest neighbours and expand outward.
+        let lower_bound = 0;
+        let upper_bound = lut.len() - 1;
+        let target = OrderedFloat(target_value);
+        let idx = lut.partition_point(|item| item.value < target);
+        let mut left = RangedIndex::new(idx, lower_bound, upper_bound);
+        let mut right = left.clone();
+        left.dec();
+
+        // Expand outward non-symmetrically: at each step compare the two
+        // candidates on each side and advance the one that is closer to the target.  
+        // This guarantees items are visited in strictly increasing
+        // difference order, so the first N items within tolerance are exactly
+        // the N best matches.
+        loop {
+            // Check result count
+            if bucket.len() >= count_limit {
+                break;
+            }
+
+            let go_left = if left.in_range() {
+                if right.in_range() {
+                    let left_item = &lut[left.position()];
+                    let left_diff = CircuitEvaluation::from_circuit_value(left_item.value(),target_value)?.unsigned_difference;
+                    let right_item = &lut[right.position()];
+                    let right_diff = CircuitEvaluation::from_circuit_value(right_item.value(), target_value)?.unsigned_difference;
+                    left_diff <= right_diff
+                } else {
+                    true
+                }
+            } else {
+                if right.in_range() {
+                    false
+                } else {
+                    break;
+                }
+            };
+
+            let item = if go_left {
+                let item = &lut[left.position()];
+                left.dec();
+                item
+            } else {
+                let item = &lut[right.position()];
+                right.inc();
+                item
+            };
+
+            let diff = CircuitEvaluation::from_circuit_value(item.value(), target_value)?.unsigned_difference;
+            // Since the LUT is sorted, values on each side only move further
+            // from target as we advance.  Once one side exceeds tolerance,
+            // the rest of that side is guaranteed out of range.
+            if diff > request.get_tolerance() {
+                break;
+            }
+
+            bucket.push(item.circuit().clone());
+        }
+
+        Ok(Response::new(request, bucket.into_iter())?)
+    }
+}
+
+impl Resolver for LutResolver {
+    fn resolve(&self, request: &Request) -> Result<Response, ResolverError> {
+        Ok(self.intern_resolve(request)?)
+    }
+}
+
+// endregion
+
+// endregion
+
+// region: Ranged Index Helper
+
+/// The ranged index for bisect LUT finding in resolver.
+#[derive(Debug, Clone)]
+pub struct RangedIndex {
+    pos: Option<usize>,
+    lower_bound: usize,
+    upper_bound: usize,
+}
+
+impl RangedIndex {
+    /// Build ranged index with position, lower and upper bound.
+    pub fn new(pos: usize, lower_bound: usize, upper_bound: usize) -> Self {
+        let pos = if pos < lower_bound || pos > upper_bound {
+            None
+        } else {
+            Some(pos)
+        };
+
+        Self {
+            pos,
+            lower_bound,
+            upper_bound,
+        }
+    }
+
+    /// Check if the index is in range. True if it is, otherwise false.
+    pub fn in_range(&self) -> bool {
+        self.pos.is_some()
+    }
+
+    /// Get the index as usize.
+    ///
+    /// # Panics
+    ///
+    /// Panic if index is out of range.
+    pub fn position(&self) -> usize {
+        self.pos.expect("unexpected out of range index")
+    }
+
+    /// Increment the index. Return true if the index is advanced.
+    pub fn inc(&mut self) -> bool {
+        match self.pos {
+            Some(pos) => {
+                self.pos = if pos >= self.upper_bound {
+                    None
+                } else {
+                    Some(pos + 1)
+                };
+                true
+            }
+            None => false,
+        }
+    }
+
+    /// Decrement the index. Return true if the index is advanced.
+    pub fn dec(&mut self) -> bool {
+        match self.pos {
+            Some(pos) => {
+                self.pos = if pos <= self.lower_bound {
+                    None
+                } else {
+                    Some(pos - 1)
+                };
+                true
+            }
+            None => false,
+        }
+    }
+}
+
+// endregion

kernel/lcrconn/src/spec.rs

@@ -0,0 +1,496 @@
+//! Types for managing the rated values of components available in your lab.
+//!
+//! In this module, a "spec" means a single rated parameter value of a component,
+//! such as `100` Ohms, `4.7k` Ohms, or `10u` Farads. It is **not** a general
+//! technical specification document — it is simply the nominal value printed on
+//! the component's body.
+//!
+//! - [`Spec`] — one rated value (e.g., 4.7k).
+//! - [`SpecGroup`] — all rated values of a given component type that your lab
+//!   actually has in stock (e.g., all resistor values available in your drawer).
+//! - [`SpecCatalog`] — the complete collection of rated values for resistors,
+//!   capacitors, and inductors.
+//!
+//! In short: these types answer the question "which exact component values can
+//! I pick from the shelf?".
+
+use crate::common::{
+    DeviceValueError, FloatingPointError, validate_device_value, validate_floating_point,
+};
+use ordered_float::OrderedFloat;
+use std::collections::HashSet;
+use std::fs::File;
+use std::io::{BufRead, BufReader, BufWriter, Error as IoError, Write};
+use std::num::ParseFloatError;
+use std::path::Path;
+use thiserror::Error as TeError;
+
+/// Errors that can occur when working with rated component values.
+#[derive(Debug, TeError)]
+pub enum SpecError {
+    #[error("invalid device value: {0}")]
+    BadDeviceValue(#[from] DeviceValueError),
+    #[error("bad string form of device value: {0}")]
+    ParseHumanReadableValue(#[from] ParseHumanReadableValueError),
+    #[error("duplicate rated value: {0}")]
+    DupSpecItem(String),
+    #[error("empty rated value group")]
+    EmptySpecGroup,
+    #[error("fail to open rated values file: {0}")]
+    OpenSpecFile(IoError),
+    #[error("fail to read rated values file: {0}")]
+    ReadSpecFile(IoError),
+    #[error("fail to write rated values file: {0}")]
+    WriteSpecFile(IoError),
+}
+
+/// One rated value of a component (e.g., `4.7k` standing for 4700 Ohms).
+///
+/// A `Spec` stores both the parsed numeric value and the original human-readable
+/// string so that the value can be re-serialized exactly as it was entered.
+#[derive(Debug, Clone)]
+struct Spec {
+    /// The numeric rated value (e.g., `4700.0` for `"4.7k"`).
+    value: f64,
+    /// The original human-readable form (e.g., `"4.7k"`), kept for faithful
+    /// round-trip serialization.
+    str_value: String,
+}
+
+impl Spec {
+    /// Create a new rated value from its human-readable representations.
+    pub fn new(str_value: String) -> Result<Self, SpecError> {
+        // Try parsing value and check its range
+        let value = from_human_readable_value(&str_value)?;
+        let value = validate_device_value(value)?;
+        Ok(Self { value, str_value })
+    }
+
+    /// Get the numeric rated value (e.g., `4700.0` for `"4.7k"`).
+    pub fn get_value(&self) -> f64 {
+        self.value
+    }
+
+    /// Get the original human-readable value form (e.g., `"4.7k"`).
+    pub fn get_str_value(&self) -> &str {
+        &self.str_value
+    }
+}
+
+/// All rated values that your lab stocks for a single component type.
+///
+/// For example, a `SpecGroup` for resistors might hold `{100, 220, 470, 1k, 4.7k, 10k}`
+/// — these are the actual resistor values you have on hand. The same concept applies
+/// to capacitors and inductors.
+pub struct SpecGroup {
+    /// The rated values belonging to this group.
+    specs: Vec<Spec>,
+}
+
+impl SpecGroup {
+    /// Internal constructor: parse and deduplicate a sequence of human-readable rated values.
+    fn new<I>(str_values: I) -> Result<Self, SpecError>
+    where
+        I: IntoIterator<Item = String>,
+    {
+        // Check string form value one by one
+        let mut specs: Vec<Spec> = Vec::new();
+        let mut seen: HashSet<OrderedFloat<f64>> = HashSet::new();
+
+        for str_value in str_values {
+            // Build spec instance
+            let spec = Spec::new(str_value)?;
+            // Check and update set
+            if !seen.insert(OrderedFloat(spec.get_value())) {
+                return Err(SpecError::DupSpecItem(spec.get_str_value().to_string()));
+            }
+            // Add into result
+            specs.push(spec);
+        }
+
+        // Check empty case
+        if specs.is_empty() {
+            return Err(SpecError::EmptySpecGroup);
+        }
+
+        // Ok, assign it
+        Ok(Self { specs })
+    }
+
+    /// Build a spec group from any iterable of human-readable rated values (e.g., `"4.7k"`, `"100"`).
+    pub fn from_iterator<I, S>(str_values: I) -> Result<Self, SpecError>
+    where
+        I: IntoIterator<Item = S>,
+        S: Into<String>,
+    {
+        Self::new(str_values.into_iter().map(|i| i.into()))
+    }
+
+    /// Read rated values from a text block, one value per non-empty line.
+    pub fn from_text(text: &str) -> Result<Self, SpecError> {
+        let lines = text
+            .lines()
+            .map(|line| line.trim().to_string())
+            .filter(|line| !line.is_empty());
+        Self::from_iterator(lines)
+    }
+
+    /// Read rated values from a file, one value per non-empty line.
+    pub fn from_file<P>(path: P) -> Result<Self, SpecError>
+    where
+        P: AsRef<Path>,
+    {
+        let file = File::open(path).map_err(|err| SpecError::OpenSpecFile(err))?;
+        let reader = BufReader::new(file);
+        let lines = reader
+            .lines()
+            .map(|line| line.map(|line| line.trim().to_string()))
+            .filter(|line| !matches!(line, Ok(line) if line.is_empty()))
+            .collect::<Result<Vec<_>, _>>()
+            .map_err(|err| SpecError::ReadSpecFile(err))?;
+        Self::from_iterator(lines.into_iter())
+    }
+
+    /// A commonly used set of resistor rated values (E12‑derived).
+    pub fn resistor_preset() -> Self {
+        Self::from_iterator([
+            "100", "220", "270", "390", "470", "680", "1k", "1.2k", "1.5k", "2.2k", "3.3k", "4.7k",
+            "6.8k", "10k", "47k", "100k", "1M",
+        ]).expect("unexpected bad rated values preset")
+    }
+
+    /// A commonly used set of capacitor rated values.
+    pub fn capacitor_preset() -> Self {
+        Self::from_iterator([
+            "10p", "22p", "33p", "47p", "68p", "100p", "150p", "220p", "330p", "470p", "560p",
+            "1u", "2.2u", "3.3u", "4.7u", "10u", "22u", "47u", "100u", "220u", "470u",
+        ]).expect("unexpected bad rated values preset")
+    }
+
+    /// A commonly used set of inductor rated values.
+    pub fn inductor_preset() -> Self {
+        Self::from_iterator([
+            "0.1u", "0.15u", "0.47u", "0.68u", "1u", "1.5u", "2.2u", "3.3u", "4.7u", "6.8u",
+            "8.2u", "10u", "15u", "22u", "33u", "47u", "68u", "100u",
+        ]).expect("unexpected bad rated values preset")
+    }
+
+    fn save(&self) -> impl Iterator<Item = &str> {
+        self.specs.iter().map(|i| i.str_value.as_str())
+    }
+
+    /// Iterate over the human-readable form of every rated value (for re-serialization).
+    pub fn save_iterator(&self) -> impl Iterator<Item = &str> {
+        self.save()
+    }
+
+    /// Join all rated values with newlines into a single string (for re-serialization).
+    pub fn save_text(&self) -> String {
+        itertools::join(self.save_iterator(), "\n")
+    }
+
+    /// Write all rated values to a file, one per line.
+    pub fn save_file<P>(&self, path: P) -> Result<(), SpecError>
+    where
+        P: AsRef<Path>,
+    {
+        let file = File::open(path).map_err(|err| SpecError::OpenSpecFile(err))?;
+        let mut writer = BufWriter::new(file);
+        for line in self.save_iterator() {
+            writer
+                .write_all(line.as_bytes())
+                .map_err(|err| SpecError::WriteSpecFile(err))?;
+            writer
+                .write_all("\n".as_bytes())
+                .map_err(|err| SpecError::WriteSpecFile(err))?;
+        }
+        Ok(())
+    }
+
+    /// How many rated values this group contains.
+    pub fn len(&self) -> usize {
+        self.specs.len()
+    }
+
+    /// Get the numeric rated value at the given index.
+    pub fn get(&self, index: usize) -> Option<f64> {
+        self.specs.get(index).map(|i| i.value)
+    }
+
+    /// Iterate over all numeric rated values in this group.
+    pub fn iter(&self) -> impl Iterator<Item = f64> + Clone {
+        self.specs.iter().map(|i| i.value)
+    }
+}
+
+/// The full catalogue of rated component values your lab stocks.
+///
+/// Bundles three [`SpecGroup`]s — one each for resistors, capacitors, and
+/// inductors. This is the top-level entry point for answering "which component
+/// values are available?".
+pub struct SpecCatalog {
+    /// Rated values available for resistors.
+    resistor: SpecGroup,
+    /// Rated values available for capacitors.
+    capacitor: SpecGroup,
+    /// Rated values available for inductors.
+    inductor: SpecGroup,
+}
+
+impl SpecCatalog {
+    /// Assemble a catalogue from the three device‑type spec groups.
+    pub fn new(resistor: SpecGroup, capacitor: SpecGroup, inductor: SpecGroup) -> Self {
+        Self {
+            resistor,
+            capacitor,
+            inductor,
+        }
+    }
+
+    /// Build a catalogue from three iterables of human‑readable rated values.
+    ///
+    /// * `resistor` — values such as `"100"`, `"4.7k"`, etc.
+    /// * `capacitor` — values such as `"10p"`, `"4.7u"`, etc.
+    /// * `inductor` — values such as `"1u"`, `"10u"`, etc.
+    pub fn from_iterable<I1, S1, I2, S2, I3, S3>(
+        resistor: I1,
+        capacitor: I2,
+        inductor: I3,
+    ) -> Result<Self, SpecError>
+    where
+        I1: IntoIterator<Item = S1>,
+        S1: Into<String>,
+        I2: IntoIterator<Item = S2>,
+        S2: Into<String>,
+        I3: IntoIterator<Item = S3>,
+        S3: Into<String>,
+    {
+        Ok(Self {
+            resistor: SpecGroup::from_iterator(resistor)?,
+            capacitor: SpecGroup::from_iterator(capacitor)?,
+            inductor: SpecGroup::from_iterator(inductor)?,
+        })
+    }
+
+    /// Build a catalogue from three text blocks, one value per line.
+    ///
+    /// * `resistor` — the resistor rated‑values text.
+    /// * `capacitor` — the capacitor rated‑values text.
+    /// * `inductor` — the inductor rated‑values text.
+    pub fn from_text(resistor: &str, capacitor: &str, inductor: &str) -> Result<Self, SpecError> {
+        Ok(Self {
+            resistor: SpecGroup::from_text(resistor)?,
+            capacitor: SpecGroup::from_text(capacitor)?,
+            inductor: SpecGroup::from_text(inductor)?,
+        })
+    }
+
+    /// Build a catalogue from three files, one value per line.
+    ///
+    /// * `resistor` — path to the resistor rated‑values file.
+    /// * `capacitor` — path to the capacitor rated‑values file.
+    /// * `inductor` — path to the inductor rated‑values file.
+    pub fn from_file<P1, P2, P3>(
+        resistor: P1,
+        capacitor: P2,
+        inductor: P3,
+    ) -> Result<Self, SpecError>
+    where
+        P1: AsRef<Path>,
+        P2: AsRef<Path>,
+        P3: AsRef<Path>,
+    {
+        Ok(Self {
+            resistor: SpecGroup::from_file(resistor)?,
+            capacitor: SpecGroup::from_file(capacitor)?,
+            inductor: SpecGroup::from_file(inductor)?,
+        })
+    }
+
+    /// A ready‑to‑use catalogue with common resistor, capacitor and inductor rated values.
+    pub fn devices_preset() -> Self {
+        Self {
+            resistor: SpecGroup::resistor_preset(),
+            capacitor: SpecGroup::capacitor_preset(),
+            inductor: SpecGroup::inductor_preset(),
+        }
+    }
+
+    /// Return one save‑iterator for each of the three device types.
+    pub fn save_iterator(
+        &self,
+    ) -> (
+        impl Iterator<Item = &str>,
+        impl Iterator<Item = &str>,
+        impl Iterator<Item = &str>,
+    ) {
+        (
+            self.resistor.save_iterator(),
+            self.capacitor.save_iterator(),
+            self.inductor.save_iterator(),
+        )
+    }
+
+    /// Return the text representation of all three device‑type value sets.
+    pub fn save_text(&self) -> (String, String, String) {
+        (
+            self.resistor.save_text(),
+            self.capacitor.save_text(),
+            self.inductor.save_text(),
+        )
+    }
+
+    /// Save all three device‑type value sets to files, one value per line.
+    ///
+    /// * `resistor` — file path for the resistor values.
+    /// * `capacitor` — file path for the capacitor values.
+    /// * `inductor` — file path for the inductor values.
+    pub fn save_file<P1, P2, P3>(
+        &self,
+        resistor: P1,
+        capacitor: P2,
+        inductor: P3,
+    ) -> Result<(), SpecError>
+    where
+        P1: AsRef<Path>,
+        P2: AsRef<Path>,
+        P3: AsRef<Path>,
+    {
+        self.resistor.save_file(resistor)?;
+        self.capacitor.save_file(capacitor)?;
+        self.inductor.save_file(inductor)?;
+        Ok(())
+    }
+
+    /// Access the resistor rated‑value set.
+    pub fn resistor_specs(&self) -> &SpecGroup {
+        &self.resistor
+    }
+
+    /// Access the capacitor rated‑value set.
+    pub fn capacitor_specs(&self) -> &SpecGroup {
+        &self.capacitor
+    }
+
+    /// Access the inductor rated‑value set.
+    pub fn inductor_specs(&self) -> &SpecGroup {
+        &self.inductor
+    }
+}
+
+// region: Human Readable Value
+
+#[derive(Debug, TeError)]
+pub enum ParseHumanReadableValueError {
+    #[error("fail to parse floating point part of given human readable value: {0}")]
+    ParseFloat(#[from] ParseFloatError),
+    #[error("arithmetic error: {0}")]
+    BadArithmetic(#[from] FloatingPointError),
+}
+
+/// Convert human readable value to float.
+///
+/// `strl` is the human readable value.
+/// The return value is the parsed float value. or error occurs when parsing.
+///
+/// This function guarantee that return value must be a valid floating value.
+/// But do not guarantee that it can be used as device value.
+/// It is possible that it is negative or zero floating point value.
+pub fn from_human_readable_value(strl: &str) -> Result<f64, ParseHumanReadableValueError> {
+    let strl = strl.trim();
+
+    let (num_part, multiplier) = if let Some(stripped) = strl.strip_suffix('n') {
+        (stripped, 1e-12)
+    } else if let Some(stripped) = strl.strip_suffix('p') {
+        (stripped, 1e-9)
+    } else if let Some(stripped) = strl.strip_suffix('u') {
+        (stripped, 1e-6)
+    } else if let Some(stripped) = strl.strip_suffix('m') {
+        (stripped, 1e-3)
+    } else if let Some(stripped) = strl.strip_suffix('k') {
+        (stripped, 1e3)
+    } else if let Some(stripped) = strl.strip_suffix('M') {
+        (stripped, 1e6)
+    } else if let Some(stripped) = strl.strip_suffix('G') {
+        (stripped, 1e9)
+    } else {
+        (strl, 1.0)
+    };
+
+    let num = num_part.parse::<f64>()?;
+    Ok(validate_floating_point(num * multiplier)?)
+}
+
+/// The unit scale for human readable value.
+#[derive(Debug, Clone, Copy)]
+pub enum UnitScale {
+    NanoLower,
+    Nano,
+    Micro,
+    Milli,
+    None,
+    Kilo,
+    Mega,
+    Giga,
+    GigaHigher,
+}
+
+/// Get the unit scale of human readable value.
+///
+/// `v` is the value for analyzing scale.
+/// It must be a valid floating point value.
+/// 
+/// # Panics
+/// 
+/// This function panics when given floating point value is bad.
+pub fn get_human_readable_value_scale(v: f64) -> UnitScale {
+    let v = validate_floating_point(v).expect("unexpected bad floating point value");
+    let v = v.abs();
+    if v < 1e-12 {
+        UnitScale::NanoLower
+    } else if v < 1e-9 {
+        UnitScale::Nano
+    } else if v < 1e-6 {
+        UnitScale::Micro
+    } else if v < 1e-3 {
+        UnitScale::Milli
+    } else if v < 1e3 {
+        UnitScale::None
+    } else if v < 1e6 {
+        UnitScale::Kilo
+    } else if v < 1e9 {
+        UnitScale::Mega
+    } else if v < 1e12 {
+        UnitScale::Giga
+    } else {
+        UnitScale::GigaHigher
+    }
+}
+
+/// Convert float value to human readable value.
+///
+/// `v`is the float value for formatting as human readable value.
+/// It must be a valid floating point value.
+/// 
+/// # Panics
+/// 
+/// This function panics when given floating point value is bad.
+pub fn to_human_readable_value(v: f64) -> String {
+    let scale = get_human_readable_value_scale(v);
+    match scale {
+        UnitScale::NanoLower => format!("{:+.4e} n", v / 1e-12),
+        UnitScale::Nano => format!("{:+.4} p", v / 1e-9),
+        UnitScale::Micro => format!("{:+.4} u", v / 1e-6),
+        UnitScale::Milli => format!("{:+.4} m", v / 1e-3),
+        // YYC MARK:
+        // The space of this format string is by design
+        // for keeping the same style with other format strings.
+        UnitScale::None => format!("{:+.4} ", v),
+        UnitScale::Kilo => format!("{:+.4} k", v / 1e3),
+        UnitScale::Mega => format!("{:+.4} M", v / 1e6),
+        UnitScale::Giga => format!("{:+.4} G", v / 1e9),
+        UnitScale::GigaHigher => format!("{:+.4e} G", v / 1e9),
+    }
+}
+
+// endregion

kernel/lcrconn/tests/spec.rs

@@ -0,0 +1,11 @@
+use lcrconn::spec;
+
+#[test]
+fn test_spec_preset() {
+    // All individual preset and catalog preset should nit panic
+    let _ = spec::SpecGroup::resistor_preset();
+    let _ = spec::SpecGroup::capacitor_preset();
+    let _ = spec::SpecGroup::inductor_preset();
+
+    let _ = spec::SpecCatalog::devices_preset();
+}

legacy/README.md

@@ -1,5 +1,54 @@
 # LCR Connector (Legacy)
 
-在3个元器件内，使用给定元器件数值列表快速找到目标数值元器件的最好拼接方式，支持电阻，电容，电感
+Get the resistor, capacitor, or inductor circuit which has the closest value for your given value within at most 3 devices.
 
-执行`uv run lcr-connector --help`来查阅参数手册。
+This is the legacy version of LCR Connector, although this is also refactored from true legacy version in modern Python.
+
+## Usage
+
+- Execute `uv sync` to configure the environment.
+- Execute `uv run lcr-connector --help` for the usage of LCR Connector.
+- After launch LCR Connector, you can see the help message in interactive console, or type `help` to see the help message.
+
+A small hint for you: `lut` resolver is good and quick on most devices.
+However, if you are running on memory-limited device, `bfs` resolver may be the substitute for you.
+
+Additionaly, for using LCR Connector, you need 3 list files holding all possible device standard values which are available in your laboratory.
+Each of them represents a type of device respectively, resistor, capacitor, or inductor.
+These list files are basically like this:
+
+```
+100
+220
+270
+390
+470
+680
+1k
+1.2k
+1.5k
+2.2k
+3.3k
+4.7k
+6.8k
+10k
+47k
+100k
+1M
+```
+
+Supported units are:
+
+- n: Nano
+- p: Pico
+- u: Micro
+- m: Milli
+- k: Kilo
+- M: Mega
+- G: Giga
+
+There is no physical unit for the values in the list files.
+
+Unit is optional. If you don't specify a unit, the value is considered as a plain floating value.
+
+Unit is **case sensitive** to distinguish between milli and mega (e.g. 1m is milli, 1M is mega).

legacy/pyproject.toml

@@ -1,7 +1,7 @@
 [project]
 name = "lcr-connector"
 version = "1.0.0"
-description = "Use as much 3 devices to reach target value for resistor, capacitor and inductor."
+description = "Get the resistor, capacitor, or inductor circuit which has the closest value for your given value within at most 3 devices."
 readme = "README.md"
 authors = [
     { name = "yyc12345", email = "yyc12321@outlook.com" }

legacy/src/lcr_connector/__init__.py

@@ -9,8 +9,8 @@ from .dataset import (
     to_human_readable_value,
     from_human_readable_value,
 )
-from .query import Request, ResponsePriority, Response
-from .resolver import Resolver, LutResolver, AStarResolver
+from .query import Request, ResponsePriority, Response, MAX_RESPONSE_CNT
+from .resolver import Resolver, LutResolver, BfsResolver
 
 _TStrEnum = TypeVar("_TStrEnum", bound=enum.StrEnum)
 
@@ -22,11 +22,11 @@ class AppResolver(enum.StrEnum):
 
     LUT = "lut"
     """The look-up table resolver."""
-    ASTAR = "astar"
-    """The A* resolver."""
+    BFS = "bfs"
+    """The BFS resolver."""
 
 
-@dataclass
+@dataclass(frozen=True)
 class AppConfig:
     """
     The configuration for the app.
@@ -65,8 +65,8 @@ class App:
         match self.__config.resolver:
             case AppResolver.LUT:
                 self.__resolver = LutResolver(self.__dataset)
-            case AppResolver.ASTAR:
-                self.__resolver = AStarResolver(self.__dataset)
+            case AppResolver.BFS:
+                self.__resolver = BfsResolver(self.__dataset)
 
     def run(self) -> None:
         """
@@ -76,6 +76,8 @@ class App:
         print('Type "help" for more info. Type "exit" to quit.')
         self.__op_main()
 
+    # region: Subcommand Processors
+
     class MainCmd(enum.StrEnum):
         QUERY = "query"
         HELP = "help"
@@ -143,14 +145,19 @@ class App:
         tolerance = self.__accept_device_value_tolerance(target_value)
 
         print("How to sort result?")
-        print("l: less component")
         print("a: more accuracy")
+        print("l: less component")
         response_priority = self.__accept_command(
             App.QuerySortPriority
         ).to_response_priority()
 
+        print("How may result are you expected?")
+        count_limit = self.__accept_count_value()
+
         # build request and ask resolver
-        request = Request(device_kind, target_value, tolerance, response_priority, 100)
+        request = Request(
+            device_kind, target_value, tolerance, response_priority, count_limit
+        )
         response = self.__resolver.resolve(request)
 
         # use page viewer to show result
@@ -174,17 +181,8 @@ class App:
                 index = current_page * (ITEMS_PER_PAGE - 1) + i
                 if index >= cnt:
                     continue
-                # fetch item and print it
-                item = response[index]
-                print(
-                    "Plan {0}\tValue: {1}\tDiff: {2} ({3:.2%})".format(
-                        index + 1,
-                        to_human_readable_value(item.value),
-                        to_human_readable_value(item.difference),
-                        item.relative_difference,
-                    )
-                )
-                self.__illustrate_circuit(item.circuit)
+                # and print it
+                self.__illustrate_response(response, index)
 
             # print page footer
             print("")
@@ -199,6 +197,10 @@ class App:
                 case App.PageViewerCmd.QUIT:
                     break
 
+    # endregion
+
+    # region: Command Utilities
+
     def __accept_command(self, cmd_enum: type[_TStrEnum]) -> _TStrEnum:
         """
         Accept a command from the user.
@@ -217,10 +219,31 @@ class App:
             except ValueError:
                 print("Unknown command, please try again.")
 
+    def __accept_count_value(self) -> int:
+        while True:
+            self.__show_prompt_arrow()
+            words = input()
+            if words == "":
+                continue
+
+            try:
+                value = int(words)
+            except ValueError:
+                print("Wrong value, please try again.")
+                continue
+
+            if value > MAX_RESPONSE_CNT or value <= 0:
+                print("Wrong value, please try again.")
+            else:
+                return value
+
     def __accept_device_value(self) -> float:
         while True:
             self.__show_prompt_arrow()
             words = input()
+            if words == "":
+                continue
+
             value = self.__parse_human_readable_value(words)
             if value is None:
                 print("Wrong value, please try again.")
@@ -231,6 +254,8 @@ class App:
         while True:
             self.__show_prompt_arrow()
             words = input()
+            if words == "":
+                continue
 
             if words.endswith("%"):
                 value = self.__parse_plain_float(
@@ -289,33 +314,145 @@ class App:
         else:
             return None
 
-    def __get_joint_kind_symbol(self, joint_kind: JointKind) -> str:
-        match joint_kind:
-            case JointKind.SERIES:
-                return "S"
-            case JointKind.PARALLEL:
-                return "P"
+    # endregion
 
-    def __illustrate_circuit(self, circuit: Circuit) -> None:
+    # region: Response Display
+
+    def __get_device_unit(self, device_kind: DeviceKind) -> str:
+        match device_kind:
+            case DeviceKind.RESISTOR:
+                # YYC MARK: This is ohm char.
+                return "\u2126"
+            case DeviceKind.CAPACITOR:
+                return "F"
+            case DeviceKind.INDUCTOR:
+                return "H"
+
+    def __to_circult_graph_value(self, value: float, device_kind: DeviceKind) -> str:
+        # Remove sign and append device unit
+        return to_human_readable_value(value)[1:] + self.__get_device_unit(device_kind)
+
+    def __to_plan_head_value(self, value: float, device_kind: DeviceKind) -> str:
+        # Remove sign and append device unit
+        return to_human_readable_value(value)[1:] + self.__get_device_unit(device_kind)
+
+    def __to_plan_head_diff(self, value: float, device_kind: DeviceKind) -> str:
+        # Keep the sign and append device unit
+        return to_human_readable_value(value) + self.__get_device_unit(device_kind)
+
+    def __to_plan_head_diff_pct(self, value: float) -> str:
+        # Keep the sign and format it as percentage style without trailing device unit
+        return "{:.2%}".format(value)
+
+    # YYC MARK:
+    # The function showing circuit graph should be maintained carefully.
+    # First, we want they are show in console properly,
+    # And we also want they have good code view.
+    #
+    # I notices that the number part of the output of `to_human_readable_value` will only be
+    # "+999.9999" or "+9.9999e+00". So its maximum of its length is 11, considering the possibility,
+    # that the absolute value of exponential part is larger than 99, is close to zero.
+    # After putting the scale unit and device unit together like " nF",
+    # the whole maximum size of the built string is 14.
+    #
+    # So we need pick a larger number and odd number for the space for showing device value,
+    # because odd value can be divided by two so it can be split as two parts equally
+    # for the convenient alignment of some circuit graphs.
+    # My picked value is 16.
+    # So you will see that I use `:^16` for a center alignment to given string.
+    #
+    # After this, we also need set the padding value carefully.
+    # This value should consider the length of f-string syntax, pre-defined chars and required chars.
+    # To make sure a pretty showcase both in code and display.
+
+    def __illustrate_response(self, response: Response, index: int) -> None:
+        """
+        Illustrate response item with given response and item.
+
+        :param response: The response to illustrate.
+        :param index: The zero-based index of the item to illustrate.
+        """
+        # fetch item and device kind from response
+        item = response[index]
+        device_kind = response.device_kind
+        # print header
+        print(
+            "Plan {0:<4} Value: {1:<16} Diff: {2} ({3})".format(
+                index + 1,
+                self.__to_plan_head_value(item.value, device_kind),
+                self.__to_plan_head_diff(item.difference, device_kind),
+                self.__to_plan_head_diff_pct(item.relative_difference),
+            )
+        )
+        # print circuit graph
+        self.__illustrate_circuit(item.circuit, device_kind)
+
+    def __illustrate_circuit(self, circuit: Circuit, device_kind: DeviceKind) -> None:
         match circuit.device_scale:
             case CircuitDeviceScale.ONE:
-                dev1 = to_human_readable_value(circuit.first_device_value)
-                print(f"{dev1}")
+                self.__illustrate_one_device_circuit(circuit, device_kind)
             case CircuitDeviceScale.TWO:
-                dev1 = to_human_readable_value(circuit.first_device_value)
-                j2 = self.__get_joint_kind_symbol(circuit.second_device_joint)
-                dev2 = to_human_readable_value(circuit.second_device_value)
-                print(f"[{j2}] ┬ {dev1}")
-                print(f"    └ {dev2}")
+                self.__illustrate_two_device_circuit(circuit, device_kind)
             case CircuitDeviceScale.THREE:
-                dev1 = to_human_readable_value(circuit.first_device_value)
-                j2 = self.__get_joint_kind_symbol(circuit.second_device_joint)
-                dev2 = to_human_readable_value(circuit.second_device_value)
-                j3 = self.__get_joint_kind_symbol(circuit.third_device_joint)
-                dev3 = to_human_readable_value(circuit.third_device_value)
-                print(f"[{j3}] ┬ [{j2}] ┬ {dev1}")
-                print(f"    │     └ {dev2}")
-                print(f"    └ {dev3}")
+                self.__illustrate_three_device_circuit(circuit, device_kind)
+
+    def __illustrate_one_device_circuit(
+        self, circuit: Circuit, device_kind: DeviceKind
+    ) -> None:
+        dev1 = self.__to_circult_graph_value(circuit.first_device_value, device_kind)
+        print(f"──[{dev1:^16}]──")
+
+    def __illustrate_two_device_circuit(
+        self, circuit: Circuit, device_kind: DeviceKind
+    ) -> None:
+        dev1 = self.__to_circult_graph_value(circuit.first_device_value, device_kind)
+        j2 = circuit.second_device_joint
+        dev2 = self.__to_circult_graph_value(circuit.second_device_value, device_kind)
+        match j2:
+            case JointKind.SERIES:
+                print(f"──[{dev1:^16}]──[{dev2:^16}]──")
+            case JointKind.PARALLEL:
+                SEP0: str = " " * (6 + (16 - 10))
+                print(f"  ┌──[{dev1:^16}]──┐  ")
+                print(f"──┤   {SEP0}       ├──")
+                print(f"  └──[{dev2:^16}]──┘  ")
+
+    def __illustrate_three_device_circuit(
+        self, circuit: Circuit, device_kind: DeviceKind
+    ) -> None:
+        dev1 = self.__to_circult_graph_value(circuit.first_device_value, device_kind)
+        j2 = circuit.second_device_joint
+        dev2 = self.__to_circult_graph_value(circuit.second_device_value, device_kind)
+        j3 = circuit.third_device_joint
+        dev3 = self.__to_circult_graph_value(circuit.third_device_value, device_kind)
+        match j2:
+            case JointKind.SERIES:
+                match j3:
+                    case JointKind.SERIES:
+                        # All in series
+                        print(f"──[{dev1:^16}]──[{dev2:^16}]──[{dev3:^16}]──")
+                    case JointKind.PARALLEL:
+                        # First series then parallel
+                        SEP0: str = "─" * (6 + ((16 - 10) // 2))
+                        SEP1: str = " " * (6 + 2 * (16 - 10))
+                        print(f"  ┌──[{dev1:^16}]──[{dev2:^16}]──┐  ")
+                        print(f"──┤   {SEP1}                     ├──")
+                        print(f"  └───{SEP0}[{dev3:^16}]{SEP0}───┘  ")
+            case JointKind.PARALLEL:
+                match j3:
+                    case JointKind.SERIES:
+                        # First parallel then series
+                        SEP0: str = " " * (6 + (16 - 10))
+                        print(f"   {SEP0}       ┌──[{dev1:^16}]──┐  ")
+                        print(f"──[{dev3:^16}]──┤   {SEP0}       ├──")
+                        print(f"   {SEP0}       └──[{dev2:^16}]──┘  ")
+                    case JointKind.PARALLEL:
+                        # All in parallel
+                        print(f"  ┌──[{dev1:^16}]──┐  ")
+                        print(f"──┼──[{dev2:^16}]──┼──")
+                        print(f"  └──[{dev3:^16}]──┘  ")
+
+    # endregion
 
 
 def main() -> None:

legacy/src/lcr_connector/common.py

@@ -1,4 +1,5 @@
 import enum
+from typing import Optional
 
 
 class LcrConnException(Exception):
@@ -267,3 +268,107 @@ class Circuit:
             return self.__third_device_subckt.device_value
         else:
             raise LcrConnException("No third device")
+
+
+class CircuitCalculator:
+    """The bunch of functions for handful circuit computation"""
+
+    __device_kind: DeviceKind
+    """The kind of the device"""
+    __target_value: float
+    """The target value"""
+
+    def __init__(self, device_kind: DeviceKind, target_value: float) -> None:
+        self.__device_kind = device_kind
+        self.__target_value = target_value
+
+    def value(self, circuit: Circuit) -> float:
+        """
+        The value of this circuit.
+
+        :param circuit: The circuit for computation.
+        :return: The value.
+        """
+        return circuit.compute(self.__device_kind)
+
+    def difference(self, circuit: Circuit, value: Optional[float] = None) -> float:
+        """
+        The signed difference between the target value and the value of this circuit.
+
+        Positive value indicates that the value of this circuit is greater than the target value.
+        Negative value indicates that the value of this circuit is less than the target value.
+
+        :param circuit: The circuit for computation.
+        :param value: The value of the circuit computed by the `value` method
+        for reducing computation steps, or None if you request this method to compute the value.
+        :return: The signed difference.
+        """
+        if value is None:
+            value = self.value(circuit)
+        return value - self.__target_value
+
+    def unsigned_difference(
+        self,
+        circuit: Circuit,
+        value: Optional[float] = None,
+        difference: Optional[float] = None,
+    ) -> float:
+        """
+        The unsigned difference between the target value and the value of this circuit.
+
+        :param circuit: The circuit for computation.
+        :param value: The value of the circuit computed by the `value` method
+        for reducing computation steps, or None if you request this method to compute the value.
+        :param difference: The difference of the circuit computed by the `difference` method
+        for reducing computation steps, or None if you request this method to compute the difference.
+        :return: The unsigned difference.
+        """
+        if difference is None:
+            difference = self.difference(circuit, value)
+        return abs(difference)
+
+    def relative_difference(
+        self,
+        circuit: Circuit,
+        value: Optional[float] = None,
+        difference: Optional[float] = None,
+    ) -> float:
+        """
+        The signed relative difference between the target value and the value of this circuit.
+
+        Positive value indicates that the value of this circuit is greater than the target value.
+        Negative value indicates that the value of this circuit is less than the target value.
+
+        :param circuit: The circuit for computation.
+        :param value: The value of the circuit computed by the `value` method
+        for reducing computation steps, or None if you request this method to compute the value.
+        :param difference: The difference of the circuit computed by the `difference` method
+        for reducing computation steps, or None if you request this method to compute the difference.
+        :return: The signed relative difference.
+        """
+        if difference is None:
+            difference = self.difference(circuit, value)
+        return difference / self.__target_value
+
+    def unsigned_relative_difference(
+        self,
+        circuit: Circuit,
+        value: Optional[float] = None,
+        difference: Optional[float] = None,
+        relative_difference: Optional[float] = None,
+    ) -> float:
+        """
+        The unsigned relative difference between the target value and the value of this circuit.
+
+        :param circuit: The circuit for computation.
+        :param value: The value of the circuit computed by the `value` method
+        for reducing computation steps, or None if you request this method to compute the value.
+        :param difference: The difference of the circuit computed by the `difference` method
+        for reducing computation steps, or None if you request this method to compute the difference.
+        :param relative_difference: The relative difference of the circuit computed by the `relative_difference` method
+        for reducing computation steps, or None if you request this method to compute the relative difference.
+        :return: The unsigned relative difference.
+        """
+        if relative_difference is None:
+            relative_difference = self.relative_difference(circuit, value, difference)
+        return abs(relative_difference)

legacy/src/lcr_connector/dataset.py

@@ -1,8 +1,26 @@
-from typing import Iterable
+import enum
+from dataclasses import dataclass
+from typing import Iterable, Iterator
 from pathlib import Path
 from .common import LcrConnException
 
 
+@dataclass(frozen=True)
+class DatasetItem:
+    value: float
+    """The actual value of this item."""
+    str_value: str
+    """The string form of this value given from original input for re-saving."""
+
+    def __post_init__(self):
+        value = self.value
+        if value <= 0:
+            raise ValueError(f"Invalid value {value} in dataset item")
+        str_value = self.str_value
+        if len(str_value) == 0:
+            raise ValueError(f"Unexpected empty string in dataset item")
+
+
 class Dataset:
     """
     A list holding available standard values for resistor, capacitor or inductor.
@@ -13,27 +31,34 @@ class Dataset:
     This list will only contain 100 and 4.7k.
     """
 
-    __values: tuple[float, ...]
+    __values: tuple[DatasetItem, ...]
     """A list of available device gauge values"""
 
-    def __init__(self, values: tuple[float, ...]):
-        # Check redundant parts
-        valueset = set(values)
-        if len(valueset) != len(values):
-            raise LcrConnException(f"Duplicate item in standard value list")
-        if len(valueset) == 0:
+    def __init__(self, str_values: Iterable[str]):
+        # Check string form value one by one
+        value_items: list[DatasetItem] = []
+        value_set: set[float] = set()
+        for str_value in str_values:
+            # Try parsing value
+            value = from_human_readable_value(str_value)
+            # Check and update set
+            if value in value_set:
+                raise LcrConnException(
+                    f"Duplicate item {str_value} in standard value list"
+                )
+            else:
+                value_set.add(value)
+            # Add into result
+            value_items.append(DatasetItem(value, str_value))
+        # Check empty case
+        if len(value_items) == 0:
             raise LcrConnException(f"Empty standard value list is not allowed")
         # Ok, assign it
-        self.__values = values
+        self.__values = tuple(value_items)
 
     @staticmethod
     def from_iterable(stringfied_values: Iterable[str]) -> "Dataset":
-        return Dataset(
-            tuple(
-                from_human_readable_value(stringfied_value)
-                for stringfied_value in stringfied_values
-            )
-        )
+        return Dataset(stringfied_values)
 
     @staticmethod
     def from_text(text: str) -> "Dataset":
@@ -47,14 +72,104 @@ class Dataset:
             legal_lines = filter(lambda line: line != "", (line.strip() for line in f))
             return Dataset.from_iterable(legal_lines)
 
+    @staticmethod
+    def resistor_preset() -> "Dataset":
+        return Dataset.from_iterable(
+            (
+                "100",
+                "220",
+                "270",
+                "390",
+                "470",
+                "680",
+                "1k",
+                "1.2k",
+                "1.5k",
+                "2.2k",
+                "3.3k",
+                "4.7k",
+                "6.8k",
+                "10k",
+                "47k",
+                "100k",
+                "1M",
+            )
+        )
+
+    @staticmethod
+    def capacitor_preset() -> "Dataset":
+        return Dataset.from_iterable(
+            (
+                "10p",
+                "22p",
+                "33p",
+                "47p",
+                "68p",
+                "100p",
+                "150p",
+                "220p",
+                "330p",
+                "470p",
+                "560p",
+                "1u",
+                "2.2u",
+                "3.3u",
+                "4.7u",
+                "10u",
+                "22u",
+                "47u",
+                "100u",
+                "220u",
+                "470u",
+            )
+        )
+
+    @staticmethod
+    def inductor_preset() -> "Dataset":
+        return Dataset.from_iterable(
+            (
+                "0.1u",
+                "0.15u",
+                "0.47u",
+                "0.68u",
+                "1u",
+                "1.5u",
+                "2.2u",
+                "3.3u",
+                "4.7u",
+                "6.8u",
+                "8.2u",
+                "10u",
+                "15u",
+                "22u",
+                "33u",
+                "47u",
+                "68u",
+                "100u",
+            )
+        )
+
+    def __save(self) -> Iterator[str]:
+        return map(lambda i: i.str_value, self.__values)
+
+    def save_iterator(self) -> Iterator[str]:
+        return self.__save()
+
+    def save_text(self) -> str:
+        return "\n".join(self.__save())
+
+    def save_file(self, filename: Path) -> None:
+        with open(filename, "w", encoding="utf-8") as f:
+            f.write(self.save_text())
+
     @property
-    def values(self) -> tuple[float, ...]:
+    def values(self) -> Iterator[float]:
         """
         Get the available standard values
 
         :return: A tuple of available standard values
         """
-        return self.__values
+        return map(lambda i: i.value, self.__values)
 
 
 class DatasetCollection:
@@ -78,6 +193,14 @@ class DatasetCollection:
     def from_iterable(
         resistor: Iterable[str], capacitor: Iterable[str], inductor: Iterable[str]
     ) -> "DatasetCollection":
+        """
+        Load the standard values for resistor, capacitor and inductor respectively from iterables.
+
+        :param resistor: The iterable to load available standard values for resistor
+        :param capacitor: The iterable to load available standard values for capacitor
+        :param inductor: The iterable to load available standard values for inductor
+        :return: The built dataset collection
+        """
         return DatasetCollection(
             Dataset.from_iterable(resistor),
             Dataset.from_iterable(capacitor),
@@ -86,6 +209,14 @@ class DatasetCollection:
 
     @staticmethod
     def from_text(resistor: str, capacitor: str, inductor: str) -> "DatasetCollection":
+        """
+        Load the standard values for resistor, capacitor and inductor respectively from strings.
+
+        :param resistor: The string to load available standard values for resistor
+        :param capacitor: The string to load available standard values for capacitor
+        :param inductor: The string to load available standard values for inductor
+        :return: The built dataset collection
+        """
         return DatasetCollection(
             Dataset.from_text(resistor),
             Dataset.from_text(capacitor),
@@ -96,14 +227,66 @@ class DatasetCollection:
     def from_file(
         resistor: Path, capacitor: Path, inductor: Path
     ) -> "DatasetCollection":
+        """
+        Load the standard values for resistor, capacitor and inductor respectively from files.
+
+        :param resistor: The file to load available standard values for resistor
+        :param capacitor: The file to load available standard values for capacitor
+        :param inductor: The file to load available standard values for inductor
+        :return: The built dataset collection
+        """
         return DatasetCollection(
             Dataset.from_file(resistor),
             Dataset.from_file(capacitor),
             Dataset.from_file(inductor),
         )
 
+    @staticmethod
+    def devices_preset() -> "DatasetCollection":
+        return DatasetCollection(
+            Dataset.resistor_preset(),
+            Dataset.capacitor_preset(),
+            Dataset.inductor_preset(),
+        )
+
+    def save_iterator(self) -> tuple[Iterator[str], Iterator[str], Iterator[str]]:
+        """
+        Get the iterator of available standard values for resistor, capacitor and inductor respectively.
+
+        :return: A tuple of iterators of available standard values for resistor, capacitor and inductor respectively.
+        """
+        return (
+            self.__resistor.save_iterator(),
+            self.__capacitor.save_iterator(),
+            self.__inductor.save_iterator(),
+        )
+
+    def save_text(self) -> tuple[str, str, str]:
+        """
+        Get the string form of available standard values for resistor, capacitor and inductor respectively.
+
+        :return: A tuple of strings of available standard values for resistor, capacitor and inductor respectively.
+        """
+        return (
+            self.__resistor.save_text(),
+            self.__capacitor.save_text(),
+            self.__inductor.save_text(),
+        )
+
+    def save_file(self, resistor: Path, capacitor: Path, inductor: Path) -> None:
+        """
+        Save the available standard values for resistor, capacitor and inductor respectively to files.
+
+        :param resistor: The file to save available standard values for resistor
+        :param capacitor: The file to save available standard values for capacitor
+        :param inductor: The file to save available standard values for inductor
+        """
+        self.__resistor.save_file(resistor)
+        self.__capacitor.save_file(capacitor)
+        self.__inductor.save_file(inductor)
+
     @property
-    def resistor_values(self) -> Dataset:
+    def resistor_dataset(self) -> Dataset:
         """
         Get the available standard values for resistor
 
@@ -112,7 +295,7 @@ class DatasetCollection:
         return self.__resistor
 
     @property
-    def capacitor_values(self) -> Dataset:
+    def capacitor_dataset(self) -> Dataset:
         """
         Get the available standard values for capacitor
 
@@ -121,7 +304,7 @@ class DatasetCollection:
         return self.__capacitor
 
     @property
-    def inductor_values(self) -> Dataset:
+    def inductor_dataset(self) -> Dataset:
         """
         Get the available standard values for inductor
 
@@ -157,6 +340,49 @@ def from_human_readable_value(strl: str) -> float:
     return float(strl)
 
 
+class UnitScale(enum.IntEnum):
+    """
+    The unit scale for human readable value
+    """
+
+    NANO_LOWER = enum.auto()
+    NANO = enum.auto()
+    MICRO = enum.auto()
+    MILLI = enum.auto()
+    NONE = enum.auto()
+    KILO = enum.auto()
+    MEGA = enum.auto()
+    GIGA = enum.auto()
+    GIGA_HIGHER = enum.auto()
+
+
+def get_human_readable_value_scale(v: float) -> UnitScale:
+    """
+    Get the unit scale of human readable value
+
+    :param v: The value
+    :return: The unit scale
+    """
+    v = abs(v)
+    if v < 1e-12:
+        return UnitScale.NANO_LOWER
+    if v < 1e-9:
+        return UnitScale.NANO
+    if v < 1e-6:
+        return UnitScale.MICRO
+    if v < 1e-3:
+        return UnitScale.MILLI
+    if v < 1e3:
+        return UnitScale.NONE
+    if v < 1e6:
+        return UnitScale.KILO
+    if v < 1e9:
+        return UnitScale.MEGA
+    if v < 1e12:
+        return UnitScale.GIGA
+    return UnitScale.GIGA_HIGHER
+
+
 def to_human_readable_value(v: float) -> str:
     """
     Convert float value to human readable value
@@ -164,21 +390,26 @@ def to_human_readable_value(v: float) -> str:
     :param value: The float value
     :return: The human readable value
     """
-    if v / 1e-12 < 1e3:
-        return "{:e} n".format(v / 1e-12)
-    if v / 1e-9 < 1e3:
-        return "{:.4f} p".format(v / 1e-9)
-    if v / 1e-6 < 1e3:
-        return "{:.4f} u".format(v / 1e-6)
-    if v / 1e-3 < 1e3:
-        return "{:.4f} m".format(v / 1e-3)
-    if v < 1e3:
-        return "{:.4f}".format(v)
-    if v / 1e3 < 1e3:
-        return "{:.4f} k".format(v / 1e3)
-    if v / 1e6 < 1e3:
-        return "{:.4f} M".format(v / 1e6)
-    if v / 1e9 < 1e3:
-        return "{:.4f} G".format(v / 1e9)
-
-    return "{:e}".format(v)
+    scale = get_human_readable_value_scale(v)
+    match scale:
+        case UnitScale.NANO_LOWER:
+            return "{:+.4e} n".format(v / 1e-12)
+        case UnitScale.NANO:
+            return "{:+.4f} p".format(v / 1e-9)
+        case UnitScale.MICRO:
+            return "{:+.4f} u".format(v / 1e-6)
+        case UnitScale.MILLI:
+            return "{:+.4f} m".format(v / 1e-3)
+        case UnitScale.NONE:
+            # YYC MARK:
+            # The space of this format string is by design
+            # for keeping the same style with other format strings.
+            return "{:+.4f} ".format(v)
+        case UnitScale.KILO:
+            return "{:+.4f} k".format(v / 1e3)
+        case UnitScale.MEGA:
+            return "{:+.4f} M".format(v / 1e6)
+        case UnitScale.GIGA:
+            return "{:+.4f} G".format(v / 1e9)
+        case UnitScale.GIGA_HIGHER:
+            return "{:+.4e} G".format(v / 1e9)

legacy/src/lcr_connector/query.py

@@ -1,8 +1,8 @@
 import enum
 from functools import cached_property
 from dataclasses import dataclass
-from typing import Iterator
-from .common import DeviceKind, Circuit
+from typing import Iterable, Iterator
+from .common import DeviceKind, Circuit, CircuitCalculator
 
 
 class ResponsePriority(enum.Enum):
@@ -16,7 +16,11 @@ class ResponsePriority(enum.Enum):
     """More accuracy is the first priority."""
 
 
-@dataclass
+MAX_RESPONSE_CNT: int = 50
+"""The maximum count for the response item count passed in request."""
+
+
+@dataclass(frozen=True)
 class Request:
     """
     All request infomation for the resolver.
@@ -33,6 +37,21 @@ class Request:
     count_limit: int
     """The limited count of results."""
 
+    def __post_init__(self):
+        target_value = self.target_value
+        if target_value <= 0:
+            raise ValueError(
+                f"Invalid value {target_value} for target value in request."
+            )
+        tolerance = self.tolerance
+        if tolerance < 0:
+            raise ValueError(f"Invalid value {tolerance} for tolerance in request.")
+        count_limit = self.count_limit
+        if count_limit <= 0 or count_limit > MAX_RESPONSE_CNT:
+            raise ValueError(
+                f"Too large or too less value {count_limit} for response count limit in request."
+            )
+
 
 class ResponseItem:
     """
@@ -41,17 +60,12 @@ class ResponseItem:
 
     __circuit: Circuit
     """The circuit of the response item."""
-    __device_kind: DeviceKind
-    """The kind of device of this circuit."""
-    __target_value: float
-    """The target value of this circuit."""
+    __ccalc: CircuitCalculator
+    """The trait for computing circuit values."""
 
-    def __init__(
-        self, circuit: Circuit, device_kind: DeviceKind, target_value: float
-    ) -> None:
+    def __init__(self, circuit: Circuit, ccalc: CircuitCalculator) -> None:
         self.__circuit = circuit
-        self.__device_kind = device_kind
-        self.__target_value = target_value
+        self.__ccalc = ccalc
 
     @property
     def circuit(self) -> Circuit:
@@ -62,7 +76,7 @@ class ResponseItem:
         """
         return self.__circuit
 
-    @cached_property
+    @property
     def device_count(self) -> int:
         """
         The device count of this circuit.
@@ -78,25 +92,55 @@ class ResponseItem:
 
         :return: The value.
         """
-        return self.__circuit.compute(self.__device_kind)
+        return self.__ccalc.value(self.__circuit)
 
     @cached_property
     def difference(self) -> float:
         """
-        The absolute difference between the target value and the value of this circuit.
+        The signed difference between the target value and the value of this circuit.
 
-        :return: The absolute difference.
+        Positive value indicates that the value of this circuit is greater than the target value.
+        Negative value indicates that the value of this circuit is less than the target value.
+
+        :return: The signed difference.
         """
-        return abs(self.__target_value - self.value)
+        return self.__ccalc.difference(self.__circuit, value=self.value)
+
+    @cached_property
+    def unsigned_difference(self) -> float:
+        """
+        The unsigned difference between the target value and the value of this circuit.
+
+        :return: The unsigned difference.
+        """
+        return self.__ccalc.unsigned_difference(
+            self.__circuit, difference=self.difference
+        )
 
     @cached_property
     def relative_difference(self) -> float:
         """
-        The relative difference between the target value and the value of this circuit.
+        The signed relative difference between the target value and the value of this circuit.
 
-        :return: The relative difference.
+        Positive value indicates that the value of this circuit is greater than the target value.
+        Negative value indicates that the value of this circuit is less than the target value.
+
+        :return: The signed relative difference.
         """
-        return self.difference / self.__target_value
+        return self.__ccalc.relative_difference(
+            self.__circuit, difference=self.difference
+        )
+
+    @cached_property
+    def unsigned_relative_difference(self) -> float:
+        """
+        The unsigned relative difference between the target value and the value of this circuit.
+
+        :return: The unsigned relative difference.
+        """
+        return self.__ccalc.unsigned_relative_difference(
+            self.__circuit, relative_difference=self.relative_difference
+        )
 
 
 class Response:
@@ -108,25 +152,32 @@ class Response:
     For getting the count of response items, please use the ``len`` function.
     """
 
+    __device_kind: DeviceKind
+    """The kind of device of this response."""
     __sorted_items: list[ResponseItem]
     """The sorted items by priority and difference."""
 
-    def __init__(self, request: Request, candidates: Iterator[Circuit]) -> None:
-        self.__sorted_items = list(
-            ResponseItem(item, request.device_kind, request.target_value)
-            for item in candidates
-        )
+    def __init__(self, request: Request, candidates: Iterable[Circuit]) -> None:
+        ccalc = CircuitCalculator(request.device_kind, request.target_value)
+        self.__device_kind = request.device_kind
+        self.__sorted_items = list(ResponseItem(item, ccalc) for item in candidates)
 
         # Sort by different strategy
         match request.response_priority:
             case ResponsePriority.LESS_DEVICES:
-                self.__sorted_items.sort(key=lambda x: (x.device_count, x.difference))
+                self.__sorted_items.sort(
+                    key=lambda x: (x.device_count, x.unsigned_difference)
+                )
             case ResponsePriority.MORE_ACCURACY:
-                self.__sorted_items.sort(key=lambda x: x.difference)
+                self.__sorted_items.sort(key=lambda x: x.unsigned_difference)
 
         # Cut item by limit
         self.__sorted_items = self.__sorted_items[: request.count_limit]
 
+    @property
+    def device_kind(self) -> DeviceKind:
+        return self.__device_kind
+
     def __getitem__(self, index: int) -> ResponseItem:
         return self.__sorted_items[index]
 

legacy/src/lcr_connector/resolver/__init__.py

@@ -1,9 +1,9 @@
 from .common import Resolver
 from .lut import LutResolver
-from .astar import AStarResolver
+from .bfs import BfsResolver
 
 __all__ = [
     'Resolver',
     'LutResolver',
-    'AStarResolver'
+    'BfsResolver'
 ]

legacy/src/lcr_connector/resolver/astar.py

@@ -1,17 +0,0 @@
-from typing import Iterator
-from .common import Resolver
-from ..dataset import DatasetCollection
-from ..common import Circuit
-from ..query import Request, Response
-
-class AStarResolver(Resolver):
-    """
-    A resolver that uses A* algorithm to find the best matching circuit.
-    """
-
-    def __init__(self, dataset: DatasetCollection):
-        pass
-
-    
-    def resolve(self, request: Request) -> Iterator[Circuit]:
-        pass

legacy/src/lcr_connector/resolver/bfs.py

@@ -0,0 +1,259 @@
+import heapq
+from itertools import chain, combinations_with_replacement, product
+from typing import Iterable, Iterator
+from functools import cached_property
+from .common import Resolver
+from ..dataset import DatasetCollection, Dataset
+from ..common import Circuit, DeviceKind, JointKind, CircuitCalculator
+from ..query import Request, Response
+
+
+class BfsItem:
+    """
+    The entry used in BFS iteration storing circuit and value.
+    """
+
+    __circuit: Circuit
+    """The circuit represented by this item."""
+    __ccalc: CircuitCalculator
+    """The trait for computing circuit values."""
+
+    def __init__(self, circuit: Circuit, ccalc: CircuitCalculator):
+        self.__circuit = circuit
+        self.__ccalc = ccalc
+
+    @property
+    def circuit(self) -> Circuit:
+        return self.__circuit
+
+    @cached_property
+    def value(self) -> float:
+        """
+        The computed value of the circuit.
+
+        :return: The computed value.
+        """
+        return self.__ccalc.value(self.__circuit)
+
+    @cached_property
+    def unsigned_difference(self) -> float:
+        """
+        The unsigned difference between the target value and the value of this circuit.
+
+        :return: The unsigned difference.
+        """
+        return self.__ccalc.unsigned_difference(self.__circuit, value=self.value)
+
+
+class ResultBucket(Iterable[BfsItem]):
+    """
+    A bounded bucket that keeps up to `N` LutItem entries with the smallest floats.
+
+    When the bucket is full, inserting a new item only succeeds if its float
+    is less than the current maximum; the maximum is then evicted.
+    """
+
+    class ResultBucketItem:
+        """
+        An item stored in a :class:`ResultBucket`.
+        """
+
+        __score: float
+        """The score associated with this item."""
+        __item: BfsItem
+        """The underlying LutItem."""
+        __seq: int
+        """
+        Monotonic counter used as a tiebreaker when scores are equal,
+        ensuring that heapq never compares :class:`LutItem` directly.
+        """
+
+        def __init__(self, score: float, item: BfsItem, seq: int):
+            self.__score = score
+            self.__item = item
+            self.__seq = seq
+
+        @property
+        def score(self) -> float:
+            """The score associated with this item."""
+            return self.__score
+
+        @property
+        def item(self) -> BfsItem:
+            """The underlying LutItem."""
+            return self.__item
+
+        def __lt__(self, other: "ResultBucket.ResultBucketItem") -> bool:
+            # heapq is a min-heap: it always pops the smallest element.
+            # We invert the comparison so that an item with a larger score
+            # is considered "smaller", effectively turning the min-heap
+            # into a max-heap (largest-score item at the top).
+            if self.__score != other.__score:
+                return self.__score > other.__score
+            # Counter tiebreaker: when scores are equal the later-inserted
+            # item (higher seq) is considered "smaller" and gets evicted first.
+            return self.__seq > other.__seq
+
+    __n: int
+    """Maximum number of items the bucket can hold."""
+    __heap: list[ResultBucketItem]
+    """
+    Min-heap of :class:`ResultBucketItem`.  The heap invariant is inverted
+    via :meth:`ResultBucketItem.__lt__` so the entry with the largest score
+    sits at index 0.
+    """
+    __counter: int
+    """
+    Monotonic counter fed to each :class:`ResultBucketItem` as a tiebreaker,
+    preventing heapq from comparing :class:`LutItem` on score collisions.
+    """
+
+    def __init__(self, n: int):
+        self.__n = n
+        self.__heap = []
+        self.__counter = 0
+
+    def __len__(self) -> int:
+        return len(self.__heap)
+
+    def __iter__(self) -> Iterator[BfsItem]:
+        for entry in self.__heap:
+            yield entry.item
+
+    def insert(self, item: BfsItem, score: float) -> bool:
+        """
+        Insert a :class:`LutItem` with the given score.
+
+        If the bucket is not yet full the item is always inserted.
+        Otherwise the item is only inserted when *score* is smaller
+        than the largest score currently in the bucket; the entry
+        with the largest score is then evicted.
+
+        :param item: The LutItem to insert.
+        :param score: The score associated with the item.
+        :return: ``True`` if the item was inserted, ``False`` otherwise.
+        """
+        entry = ResultBucket.ResultBucketItem(score, item, self.__counter)
+        if len(self.__heap) < self.__n:
+            heapq.heappush(self.__heap, entry)
+            self.__counter += 1
+            return True
+        if score >= self.__heap[0].score:
+            return False
+        heapq.heapreplace(self.__heap, entry)
+        self.__counter += 1
+        return True
+
+
+class BfsResolver(Resolver):
+    __datasets: DatasetCollection
+
+    def __init__(self, datasets: DatasetCollection):
+        self.__datasets = datasets
+
+    # YYC MARK:
+    # Some circuit are equivalent in topology.
+    # If we deduplicate these equaivalent circuit in building result,
+    # there are too complex works.
+    # So we should deduplicated these equivalent circuit at the beginning,
+    # i.e. when generating them.
+    # So following 3 function are taking this job.
+
+    @staticmethod
+    def iter_one_device_circuit(dataset: Dataset) -> Iterator[Circuit]:
+        """
+        Iterate all possible circuits with one device without repeating equivalent topology.
+
+        :param dataset: The dataset to iterate.
+        :return: The iterator of circuits with one device.
+        """
+        # Every single device is unique so we directly output them.
+        # This feature is insured by dataset itself.
+        return (Circuit.from_one_device(v1) for v1 in dataset.values)
+
+    @staticmethod
+    def iter_two_devices_circuit(dataset: Dataset) -> Iterator[Circuit]:
+        """
+        Iterate all possible circuits with two devices without repeating equivalent topology.
+
+        :param dataset: The dataset to iterate.
+        :return: The iterator of circuits with two devices.
+        """
+        # The two devices in this circuit is always swapable,
+        # so we iterate them without repeating.
+        return (
+            Circuit.from_two_devices(v1, v2, j2)
+            for (v1, v2), j2 in product(
+                combinations_with_replacement(dataset.values, 2),
+                tuple(JointKind),
+            )
+        )
+
+    @staticmethod
+    def iter_three_devices_circuit(dataset: Dataset) -> Iterator[Circuit]:
+        """
+        Iterate all possible circuits with three devices without repeating equivalent topology.
+
+        :param dataset: The dataset to iterate.
+        :return: The iterator of circuits with three devices.
+        """
+        # For generating three devices circuit,
+        # it should be consisted by 2 parts.
+        return chain(
+            # First, the whole circuit has only one joint type.
+            # In this case, 3 devices are swapable and we should iterate them without repeating
+            (
+                Circuit.from_three_devices(v1, v2, j, v3, j)
+                for (v1, v2, v3), j in product(
+                    combinations_with_replacement(dataset.values, 3),
+                    tuple(JointKind),
+                )
+            ),
+            # Second, if the joint type is different, then the first 2 devices are swapable.
+            # So we need iterate them without repeating.
+            (
+                Circuit.from_three_devices(v1, v2, j, v3, j.flip())
+                for (v1, v2), v3, j in product(
+                    combinations_with_replacement(dataset.values, 2),
+                    dataset.values,
+                    tuple(JointKind),
+                )
+            ),
+        )
+
+    @staticmethod
+    def __bfs_iteration(
+        dataset: Dataset, ccalc: CircuitCalculator
+    ) -> Iterator[BfsItem]:
+        return (
+            BfsItem(circuit, ccalc)
+            for circuit in chain(
+                BfsResolver.iter_one_device_circuit(dataset),
+                BfsResolver.iter_two_devices_circuit(dataset),
+                BfsResolver.iter_three_devices_circuit(dataset),
+            )
+        )
+
+    def resolve(self, request: Request) -> Response:
+        # Pick dataset from collection
+        dataset: Dataset
+        match request.device_kind:
+            case DeviceKind.RESISTOR:
+                dataset = self.__datasets.resistor_dataset
+            case DeviceKind.CAPACITOR:
+                dataset = self.__datasets.capacitor_dataset
+            case DeviceKind.INDUCTOR:
+                dataset = self.__datasets.inductor_dataset
+
+        # Iterate circuit item one by one
+        bucket = ResultBucket(request.count_limit)
+        ccalc = CircuitCalculator(request.device_kind, request.target_value)
+        for item in BfsResolver.__bfs_iteration(dataset, ccalc):
+            # If circuit absolute difference is out of tolerance, skip it directly.
+            if item.unsigned_difference > request.tolerance:
+                continue
+            # put it into bucket
+            bucket.insert(item, item.unsigned_difference)
+
+        # Return result
+        return Response(request, map(lambda item: item.circuit, bucket))

legacy/src/lcr_connector/resolver/lut.py

@@ -1,10 +1,9 @@
-import heapq
-from itertools import chain, product
-from typing import Iterable, Iterator
-from functools import cached_property
+import bisect
+from itertools import chain
 from .common import Resolver
+from .bfs import BfsResolver
 from ..dataset import DatasetCollection, Dataset
-from ..common import Circuit, DeviceKind, JointKind
+from ..common import Circuit, DeviceKind, CircuitCalculator
 from ..query import Request, Response
 
 
@@ -15,125 +14,20 @@ class LutItem:
 
     __circuit: Circuit
     """The circuit represented by this item."""
-    __device_kind: DeviceKind
-    """The device kind applied for this circuit."""
+    __value: float
+    """The value of this circuit."""
 
     def __init__(self, circuit: Circuit, device_kind: DeviceKind):
         self.__circuit = circuit
-        self.__device_kind = device_kind
+        self.__value = self.__circuit.compute(device_kind)
 
     @property
     def circuit(self) -> Circuit:
         return self.__circuit
 
-    @cached_property
+    @property
     def value(self) -> float:
-        """
-        The computed value of the circuit.
-
-        :return: The computed value.
-        """
-        return self.__circuit.compute(self.__device_kind)
-
-
-class ResultBucket(Iterable[LutItem]):
-    """
-    A bounded bucket that keeps up to `N` LutItem entries with the smallest floats.
-
-    When the bucket is full, inserting a new item only succeeds if its float
-    is less than the current maximum; the maximum is then evicted.
-    """
-
-    class ResultBucketItem:
-        """
-        An item stored in a :class:`ResultBucket`.
-        """
-
-        __score: float
-        """The score associated with this item."""
-        __item: LutItem
-        """The underlying LutItem."""
-        __seq: int
-        """
-        Monotonic counter used as a tiebreaker when scores are equal,
-        ensuring that heapq never compares :class:`LutItem` directly.
-        """
-
-        def __init__(self, score: float, item: LutItem, seq: int):
-            self.__score = score
-            self.__item = item
-            self.__seq = seq
-
-        @property
-        def score(self) -> float:
-            """The score associated with this item."""
-            return self.__score
-
-        @property
-        def item(self) -> LutItem:
-            """The underlying LutItem."""
-            return self.__item
-
-        def __lt__(self, other: "ResultBucket.ResultBucketItem") -> bool:
-            # heapq is a min-heap: it always pops the smallest element.
-            # We invert the comparison so that an item with a larger score
-            # is considered "smaller", effectively turning the min-heap
-            # into a max-heap (largest-score item at the top).
-            if self.__score != other.__score:
-                return self.__score > other.__score
-            # Counter tiebreaker: when scores are equal the later-inserted
-            # item (higher seq) is considered "smaller" and gets evicted first.
-            return self.__seq > other.__seq
-
-    __n: int
-    """Maximum number of items the bucket can hold."""
-    __heap: list[ResultBucketItem]
-    """
-    Min-heap of :class:`ResultBucketItem`.  The heap invariant is inverted
-    via :meth:`ResultBucketItem.__lt__` so the entry with the largest score
-    sits at index 0.
-    """
-    __counter: int
-    """
-    Monotonic counter fed to each :class:`ResultBucketItem` as a tiebreaker,
-    preventing heapq from comparing :class:`LutItem` on score collisions.
-    """
-
-    def __init__(self, n: int):
-        self.__n = n
-        self.__heap = []
-        self.__counter = 0
-
-    def __len__(self) -> int:
-        return len(self.__heap)
-
-    def __iter__(self) -> Iterator[LutItem]:
-        for entry in self.__heap:
-            yield entry.item
-
-    def insert(self, item: LutItem, score: float) -> bool:
-        """
-        Insert a :class:`LutItem` with the given score.
-
-        If the bucket is not yet full the item is always inserted.
-        Otherwise the item is only inserted when *score* is smaller
-        than the largest score currently in the bucket; the entry
-        with the largest score is then evicted.
-
-        :param item: The LutItem to insert.
-        :param score: The score associated with the item.
-        :return: ``True`` if the item was inserted, ``False`` otherwise.
-        """
-        entry = ResultBucket.ResultBucketItem(score, item, self.__counter)
-        if len(self.__heap) < self.__n:
-            heapq.heappush(self.__heap, entry)
-            self.__counter += 1
-            return True
-        if score >= self.__heap[0].score:
-            return False
-        heapq.heapreplace(self.__heap, entry)
-        self.__counter += 1
-        return True
+        return self.__value
 
 
 class LutResolver(Resolver):
@@ -150,38 +44,29 @@ class LutResolver(Resolver):
 
     def __init__(self, datasets: DatasetCollection):
         self.__resistor_lut = LutResolver.__build_lut(
-            datasets.resistor_values, DeviceKind.RESISTOR
+            datasets.resistor_dataset, DeviceKind.RESISTOR
         )
         self.__capacitor_lut = LutResolver.__build_lut(
-            datasets.capacitor_values, DeviceKind.CAPACITOR
+            datasets.capacitor_dataset, DeviceKind.CAPACITOR
         )
         self.__inductor_lut = LutResolver.__build_lut(
-            datasets.inductor_values, DeviceKind.INDUCTOR
+            datasets.inductor_dataset, DeviceKind.INDUCTOR
         )
 
     @staticmethod
     def __build_lut(dataset: Dataset, device_kind: DeviceKind) -> list[LutItem]:
-        values = dataset.values
-        joints = tuple(JointKind)
-        return [
+        lut = [
             LutItem(circuit, device_kind)
             for circuit in chain(
-                (Circuit.from_one_device(v1) for v1 in values),
-                (
-                    Circuit.from_two_devices(v1, v2, j2)
-                    for v1, v2, j2 in product(values, values, joints)
-                ),
-                (
-                    Circuit.from_three_devices(v1, v2, j2, v3, j3)
-                    for v1, v2, j2, v3, j3 in product(
-                        values, values, joints, values, joints
-                    )
-                ),
+                BfsResolver.iter_one_device_circuit(dataset),
+                BfsResolver.iter_two_devices_circuit(dataset),
+                BfsResolver.iter_three_devices_circuit(dataset),
             )
         ]
+        lut.sort(key=lambda item: item.value)
+        return lut
 
     def resolve(self, request: Request) -> Response:
-        # Fetch LUT by device kind
         lut: list[LutItem]
         match request.device_kind:
             case DeviceKind.RESISTOR:
@@ -191,16 +76,55 @@ class LutResolver(Resolver):
             case DeviceKind.INDUCTOR:
                 lut = self.__inductor_lut
 
-        # Check LUT item one by one
-        bucket = ResultBucket(min(request.count_limit, 100))
-        for item in lut:
-            # compute absolute difference
-            difference = abs(request.target_value - item.value)
-            # If it is out of tolerance, skip it directly.
-            if difference > request.tolerance:
-                continue
-            # put it into bucket
-            bucket.insert(item, difference)
+        target = request.target_value
+        count_limit = request.count_limit
+        bucket: list[Circuit] = []
 
-        # Return result
-        return Response(request, map(lambda item: item.circuit, bucket))
+        # Locate the insertion point of target in the sorted LUT.
+        # left/right start at the two nearest neighbours and expand outward.
+        idx = bisect.bisect_left(lut, target, key=lambda item: item.value)
+        left = idx - 1
+        right = idx
+
+        # Expand outward non-symmetrically: at each step compare the two
+        # candidates on each side and advance the one that is closer to the
+        # target.  This guarantees items are visited in strictly increasing
+        # difference order, so the first N items within tolerance are exactly
+        # the N best matches.
+        ccalc = CircuitCalculator(request.device_kind, target)
+        while left >= 0 or right < len(lut):
+            if len(bucket) >= count_limit:
+                break
+
+            if left < 0:
+                go_left = False
+            elif right >= len(lut):
+                go_left = True
+            else:
+                left_instance = lut[left]
+                left_diff = ccalc.unsigned_difference(
+                    left_instance.circuit, value=left_instance.value
+                )
+                right_instance = lut[right]
+                right_diff = ccalc.unsigned_difference(
+                    right_instance.circuit, value=right_instance.value
+                )
+                go_left = left_diff <= right_diff
+
+            if go_left:
+                item = lut[left]
+                left -= 1
+            else:
+                item = lut[right]
+                right += 1
+
+            diff = ccalc.unsigned_difference(item.circuit, value=item.value)
+            # Since the LUT is sorted, values on each side only move further
+            # from target as we advance.  Once one side exceeds tolerance,
+            # the rest of that side is guaranteed out of range.
+            if diff > request.tolerance:
+                break
+
+            bucket.append(item.circuit)
+
+        return Response(request, bucket)