annotate fft/native/native.cpp @ 40:223f770b5341 kissfft-double tip

Try a double-precision kissfft

#include <bqfft/FFT.h>

#include <vector>
#include <iostream>
#include <cmath>
#include <chrono>

using namespace std;
using namespace breakfastquay;

int main(int argc, char **argv)
{
    vector<int> sizes { 512, 2048 };

    int iterations = 2000;
    int times = 100;

    for (auto size: sizes) {

	FFT fft(size);
	double total = 0.0;

	auto start = chrono::high_resolution_clock::now();

	for (int ti = 0; ti < times; ++ti) {
	    
	    total = 0.0;

	    for (int i = 0; i < iterations; ++i) {

		vector<double> ri(size), ro(size/2+1), io(size/2+1);
		for (int j = 0; j < size; ++j) {
		    ri[j] = (j % 2) / 4.0;
		}

		fft.forward(ri.data(), ro.data(), io.data());

		for (int j = 0; j <= size/2; ++j) {
		    total += sqrt(ro[j] * ro[j] + io[j] * io[j]);
		}

		// synthesise the conjugate half
		for (int j = 1; j < size/2; ++j) {
		    total += sqrt(ro[j] * ro[j] + io[j] * io[j]);
		}
	    }
	}

	auto end = chrono::high_resolution_clock::now();

	double ms = chrono::duration<double, milli>(end - start).count() / times;
	
	cerr << "for " << iterations << " * size " << size << ": total = "
	     << total << ", time = " << ms
	     << " ms (" << (iterations / (ms / 1000.0)) << " itr/sec)" << endl;
    }
}