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@admsyn
Created August 24, 2012 16:49
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Testing vDSP's FFT vs FFTW's
#include "ofMain.h"
#include "ofxFft.h"
#include <Accelerate/Accelerate.h>
#include <mach/mach_time.h>
double mach2ms(uint64_t time)
{
mach_timebase_info_data_t timebase;
mach_timebase_info(&timebase);
return (double)time * (double)timebase.numer / (double)timebase.denom / 1e6;
}
int main() {
UInt32 min_log2N = 10;
UInt32 max_log2N = 20;
UInt32 max_N = (1 << max_log2N);
// Create re-useable vDSP bits
COMPLEX_SPLIT FFTData;
FFTData.realp = (float *) malloc(sizeof(float) * max_N/2);
FFTData.imagp = (float *) malloc(sizeof(float) * max_N/2);
float * hammingWindow = (float *) malloc(sizeof(float) * max_N);
float * A = (float *) malloc(sizeof(float) * max_N);
float * B = (float *) malloc(sizeof(float) * max_N);
FFTSetup FFTSetup = vDSP_create_fftsetup(max_log2N, kFFTRadix2);
// Create a fake signal
for(UInt32 i = 0; i < max_N; i++){
A[i] = ofRandom(-1, 1);
}
for(UInt32 log2N = min_log2N; log2N < max_log2N; log2N++)
{
UInt32 N = (1 << log2N);
// Prep vDSP
vDSP_hamm_window(hammingWindow, N, 0);
// Prep ofxFft
ofxFft * fft = ofxFft::create(N, OF_FFT_WINDOW_HAMMING, OF_FFT_FFTW);
uint64_t accel_start = mach_absolute_time();
vDSP_vmul(A, 1, hammingWindow, 1, B, 1, N); // A -> hamming -> B
vDSP_ctoz((COMPLEX *) B, 2, &FFTData, 1, N/2);
vDSP_fft_zrip(FFTSetup, &FFTData, 1, log2N, kFFTDirection_Forward);
uint64_t accel_end = mach_absolute_time();
uint64_t fftw_start = mach_absolute_time();
fft->setSignal(A);
fft->getImaginary();
uint64_t fftw_end = mach_absolute_time();
cout
<< " N = " << N
<< " Accel: " << mach2ms(accel_end - accel_start)
<< " FFTW: " << mach2ms(fftw_end - fftw_start) << endl;
delete fft;
}
free(FFTData.realp);
free(FFTData.imagp);
free(hammingWindow);
free(A);
free(B);
vDSP_destroy_fftsetup(FFTSetup);
return 0;
}
N = 1024 Accel: 0.05265 FFTW: 0.026213
N = 2048 Accel: 0.042565 FFTW: 0.049334
N = 4096 Accel: 0.049206 FFTW: 0.082782
N = 8192 Accel: 0.118918 FFTW: 0.173506
N = 16384 Accel: 0.200201 FFTW: 0.371488
N = 32768 Accel: 0.356826 FFTW: 1.01589
N = 65536 Accel: 0.844955 FFTW: 1.79316
N = 131072 Accel: 1.95759 FFTW: 3.99565
N = 262144 Accel: 4.34179 FFTW: 9.87287
N = 524288 Accel: 9.31858 FFTW: 19.6675
Specs = Mid-2009 MBP, Core 2 Duo, 2.66GHz
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