LArFFTW.cxx

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#include "lardata/Utilities/LArFFTW.h"

using std::string;

util::LArFFTW::LArFFTW(int transformSize, const void* fplan, const void* rplan, int fitbins)
  : fSize(transformSize), fPlan(fplan), rPlan(rplan), fFitBins(fitbins)
{

  fFreqSize = fSize / 2 + 1;

  // ... Real-Complex
  fIn = fftw_malloc(sizeof(double) * fSize);
  fOut = fftw_malloc(sizeof(fftw_complex) * fFreqSize);

  // ... Complex-Real
  rIn = fftw_malloc(sizeof(fftw_complex) * fFreqSize);
  rOut = fftw_malloc(sizeof(double) * fSize);

  // ... allocate other data vectors
  fCompTemp.resize(fFreqSize);
  fKern.resize(fFreqSize);
  fConvHist.resize(fFitBins);
}

util::LArFFTW::~LArFFTW()
{
  fPlan = 0;
  fftw_free(fIn);
  fIn = 0;
  fftw_free((fftw_complex*)fOut);
  fOut = 0;

  rPlan = 0;
  fftw_free((fftw_complex*)rIn);
  rIn = 0;
  fftw_free(rOut);
  rOut = 0;
}

// According to the Fourier transform identity
// f(x-a) = Inverse Transform(exp(-2*Pi*i*a*w)F(w))
// -----------------------------------------------------------------------------
void util::LArFFTW::ShiftData(ComplexVector& input, double shift)
{
  double factor = -2.0 * std::acos(-1) * shift / (double)fSize;

  for (int i = 0; i < fFreqSize; i++) {
    input[i] *= std::exp(std::complex<double>(0, factor * (double)i));
  }

  return;
}