pocketfft_demo.cc

#include <complex>
#include <cmath>
#include <vector>
#include <iostream>
#include "pocketfft_hdronly.h"

using namespace std;
using namespace pocketfft;

// floating point RNG which is good enough for simple demos
// Do not use for anything important!
inline double simple_drand()
  {
  constexpr double norm = 1./RAND_MAX;
  return rand()*norm;
  }

template<typename T> void crand(vector<complex<T>> &v)
  {
  for (auto & i:v)
    i = complex<T>(simple_drand()-0.5, simple_drand()-0.5);
  }

template<typename T1, typename T2> long double l2err
  (const vector<T1> &v1, const vector<T2> &v2)
  {
  long double sum1=0, sum2=0;
  for (size_t i=0; i<v1.size(); ++i)
    {
    long double dr = v1[i].real()-v2[i].real(),
                di = v1[i].imag()-v2[i].imag();
    long double t1 = sqrt(dr*dr+di*di), t2 = abs(v1[i]);
    sum1 += t1*t1;
    sum2 += t2*t2;
    }
  return sqrt(sum1/sum2);
  }


int main()
  {
  for (size_t len=1; len<8192; ++len)
    {
    shape_t shape{len};
    stride_t stridef(shape.size()), strided(shape.size()), stridel(shape.size());
    size_t tmpf=sizeof(complex<float>),
           tmpd=sizeof(complex<double>),
           tmpl=sizeof(complex<long double>);
    for (int i=shape.size()-1; i>=0; --i)
      {
      stridef[i]=tmpf;
      tmpf*=shape[i];
      strided[i]=tmpd;
      tmpd*=shape[i];
      stridel[i]=tmpl;
      tmpl*=shape[i];
      }
    size_t ndata=1;
    for (size_t i=0; i<shape.size(); ++i)
      ndata*=shape[i];

    vector<complex<float>> dataf(ndata);
    vector<complex<double>> datad(ndata);
    vector<complex<long double>> datal(ndata);
    crand(dataf);
    for (size_t i=0; i<ndata; ++i)
      {
      datad[i] = dataf[i];
      datal[i] = dataf[i];
      }
    shape_t axes;
    for (size_t i=0; i<shape.size(); ++i)
      axes.push_back(i);
    auto resl = datal;
    auto resd = datad;
    auto resf = dataf;
    c2c(shape, stridel, stridel, axes, FORWARD,
        datal.data(), resl.data(), 1.L);
    c2c(shape, strided, strided, axes, FORWARD,
        datad.data(), resd.data(), 1.);
    c2c(shape, stridef, stridef, axes, FORWARD,
        dataf.data(), resf.data(), 1.f);
//    c2c(shape, stridel, stridel, axes, POCKETFFT_BACKWARD,
//        resl.data(), resl.data(), 1.L/ndata);
    cout << l2err(resl, resf) << endl;
    }
  }