158 lines
5.6 KiB
C++
158 lines
5.6 KiB
C++
/*
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==============================================================================
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This file is part of the JUCE library.
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Copyright (c) 2017 - ROLI Ltd.
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JUCE is an open source library subject to commercial or open-source
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licensing.
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By using JUCE, you agree to the terms of both the JUCE 5 End-User License
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Agreement and JUCE 5 Privacy Policy (both updated and effective as of the
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27th April 2017).
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End User License Agreement: www.juce.com/juce-5-licence
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Privacy Policy: www.juce.com/juce-5-privacy-policy
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Or: You may also use this code under the terms of the GPL v3 (see
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www.gnu.org/licenses).
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JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
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EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
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DISCLAIMED.
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==============================================================================
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*/
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namespace juce
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{
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namespace dsp
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{
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template <typename FloatType>
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LookupTable<FloatType>::LookupTable()
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{
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data.resize (1);
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}
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template <typename FloatType>
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LookupTable<FloatType>::LookupTable (const std::function<FloatType (size_t)>& functionToApproximate,
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size_t numPointsToUse)
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{
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initialise (functionToApproximate, numPointsToUse);
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}
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//==============================================================================
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template <typename FloatType>
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void LookupTable<FloatType>::initialise (const std::function<FloatType (size_t)>& functionToApproximate,
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size_t numPointsToUse)
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{
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data.resize (static_cast<int> (getRequiredBufferSize (numPointsToUse)));
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for (size_t i = 0; i < numPointsToUse; ++i)
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{
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auto value = functionToApproximate (i);
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jassert (! std::isnan (value));
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jassert (! std::isinf (value));
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// Make sure functionToApproximate returns a sensible value for the entire specified range.
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// E.g., this won't work for zero: [] (size_t i) { return 1.0f / i; }
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data.getReference (static_cast<int> (i)) = value;
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}
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prepare();
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}
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template <typename FloatType>
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void LookupTable<FloatType>::prepare() noexcept
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{
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auto guardIndex = static_cast<int> (getGuardIndex());
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data.getReference (guardIndex) = data.getUnchecked (guardIndex - 1);
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}
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template <typename FloatType>
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void LookupTableTransform<FloatType>::initialise (const std::function<FloatType (FloatType)>& functionToApproximate,
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FloatType minInputValueToUse,
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FloatType maxInputValueToUse,
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size_t numPoints)
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{
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jassert (maxInputValueToUse > minInputValueToUse);
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minInputValue = minInputValueToUse;
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maxInputValue = maxInputValueToUse;
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scaler = FloatType (numPoints - 1) / (maxInputValueToUse - minInputValueToUse);
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offset = -minInputValueToUse * scaler;
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const auto initFn = [functionToApproximate, minInputValueToUse, maxInputValueToUse, numPoints] (size_t i)
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{
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return functionToApproximate (
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jlimit (
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minInputValueToUse, maxInputValueToUse,
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jmap (FloatType (i), FloatType (0), FloatType (numPoints - 1), minInputValueToUse, maxInputValueToUse))
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);
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};
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lookupTable.initialise (initFn, numPoints);
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}
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//==============================================================================
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template <typename FloatType>
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double LookupTableTransform<FloatType>::calculateMaxRelativeError (const std::function<FloatType (FloatType)>& functionToApproximate,
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FloatType minInputValue,
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FloatType maxInputValue,
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size_t numPoints,
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size_t numTestPoints)
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{
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jassert (maxInputValue > minInputValue);
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if (numTestPoints == 0)
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numTestPoints = 100 * numPoints; // use default
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LookupTableTransform transform (functionToApproximate, minInputValue, maxInputValue, numPoints);
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double maxError = 0;
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for (size_t i = 0; i < numTestPoints; ++i)
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{
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auto inputValue = jmap (FloatType (i), FloatType (0), FloatType (numTestPoints - 1), minInputValue, maxInputValue);
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auto approximatedOutputValue = transform.processSample (inputValue);
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auto referenceOutputValue = functionToApproximate (inputValue);
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maxError = jmax (maxError, calculateRelativeDifference ((double) referenceOutputValue, (double) approximatedOutputValue));
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}
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return maxError;
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}
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//==============================================================================
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template <typename FloatType>
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double LookupTableTransform<FloatType>::calculateRelativeDifference (double x, double y) noexcept
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{
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static const auto eps = std::numeric_limits<double>::min();
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auto absX = std::abs (x);
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auto absY = std::abs (y);
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auto absDiff = std::abs (x - y);
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if (absX < eps)
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{
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if (absY >= eps)
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return absDiff / absY;
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return absDiff; // return the absolute error if both numbers are too close to zero
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}
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return absDiff / std::min (absX, absY);
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}
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//==============================================================================
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template class LookupTable<float>;
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template class LookupTable<double>;
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template class LookupTableTransform<float>;
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template class LookupTableTransform<double>;
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} // namespace dsp
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} // namespace juce
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