KrotosAudioBufferDSPCorrelation.cpp

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/*
==============================================================================
 
KrotosAudioBufferDSP.cpp
Created: 13 June 2019 12:22:00am
Author:  sandyw
 
==============================================================================
*/
 
namespace krotos
{
 
    // Comparison of IPP version of crossCorrelate with software reference version
    // Typical result, IPP = 0.156485021, reference = 0.156484197
    // Very close, but not identical - doesn't matter in practice
 
    float KrotosAudioBufferDSP::crossCorrelate(const float* referencePointer, const float* candidatePointer,
                                               const int testSize)
    {
        float cross{0}; // Accumulator
        static const int GANGWIDTH{4};
        int testSizeForGangs = testSize - testSize % GANGWIDTH;
 
        // TODO: Investigate pragmas to force SIMD use, or equivalent
 
        // Iterate as much as possible gang wide ...
        int i = 0;
        for (; i < testSizeForGangs; i += GANGWIDTH)
        {
            if (threadShouldExit())
            {
                return 0.0f;
            }
            cross = cross + candidatePointer[i] * referencePointer[i];
            cross = cross + candidatePointer[i + 1] * referencePointer[i + 1];
            cross = cross + candidatePointer[i + 2] * referencePointer[i + 2];
            cross = cross + candidatePointer[i + 3] * referencePointer[i + 3];
        }
        // ... then iterate though the remainder
        for (; i < testSize; i++)
        {
            if (threadShouldExit())
            {
                return 0.0f;
            }
            cross = cross + candidatePointer[i] * referencePointer[i];
        }
        return cross / static_cast<float>(testSize);
    }
 
    float KrotosAudioBufferDSP::autoCorrelateCentred(int centerIndex, int testSize)
    {
        if (testSize <= 0)
        {
            return 0.0f;
        }
        const float* candidatePointer = getReadPointer(0) + centerIndex;
        int indexMin = centerIndex - testSize;
        if (indexMin < 0)
        {
            return 0.0f;
        }
        int indexMax = centerIndex + testSize;
        if (indexMax >= getNumSamples())
        {
            return 0.0f;
        }
        const float* referencePointer = getReadPointer(0) + indexMin;
 
        return crossCorrelate(referencePointer, candidatePointer, testSize);
    }
 
} // namespace krotos