67 lines
2.0 KiB
C++
67 lines
2.0 KiB
C++
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#include "pffft.hpp"
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#include <complex>
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#include <iostream>
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void cxx98_forward_real_float(const int transformLen)
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{
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std::cout << "running " << __FUNCTION__ << "()" << std::endl;
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// first check - might be skipped
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typedef pffft::Fft<float> FFT_T;
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if (transformLen < FFT_T::minFFtsize())
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{
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std::cerr << "Error: minimum FFT transformation length is " << FFT_T::minFFtsize() << std::endl;
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return;
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}
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// instantiate FFT and prepare transformation for length N
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pffft::Fft<float> fft(transformLen);
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// one more check
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if (!fft.isValid())
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{
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std::cerr << "Error: transformation length " << transformLen << " is not decomposable into small prime factors. "
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<< "Next valid transform size is: " << FFT_T::nearestTransformSize(transformLen)
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<< "; next power of 2 is: " << FFT_T::nextPowerOfTwo(transformLen) << std::endl;
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return;
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}
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// allocate aligned vectors for input X and output Y
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pffft::AlignedVector<float> X = fft.valueVector();
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pffft::AlignedVector< std::complex<float> > Y = fft.spectrumVector();
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// alternative access: get raw pointers to aligned vectors
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float *Xs = X.data();
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std::complex<float> *Ys = Y.data();
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// prepare some input data
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for (int k = 0; k < transformLen; k += 2)
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{
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X[k] = k; // access through AlignedVector<float>
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Xs[k+1] = -1-k; // access through raw pointer
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}
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// do the forward transform; write complex spectrum result into Y
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fft.forward(X, Y);
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// print spectral output
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std::cout << "output should be complex spectrum with " << fft.getSpectrumSize() << " bins" << std::endl;
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std::cout << "output vector has size " << Y.size() << " (complex bins):" << std::endl;
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for (unsigned k = 0; k < Y.size(); k += 2)
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{
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std::cout << "Y[" << k << "] = " << Y[k] << std::endl;
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std::cout << "Y[" << k+1 << "] = " << Ys[k+1] << std::endl;
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}
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}
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int main(int argc, char *argv[])
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{
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int N = (1 < argc) ? atoi(argv[1]) : 32;
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cxx98_forward_real_float(N);
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return 0;
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}
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