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#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "common.h"
void
discrete_fourier_transform (double *d1, double *d2, double *s1, double *s2,
double *s3, int n)
{
int mask = n-1;
double x;
double y;
int i;
int j;
for(i=0;i<n;i++){
x = 0;
y = 0;
for(j=0;j<n;j++){
x += s1[j] * s2[(i*j)&mask];
y += s1[j] * s3[(i*j)&mask];
}
d1[i] = x;
d2[i] = y;
}
}
void
complex_discrete_fourier_transform (double *d1, double *d2,
double *s1, double *s2, double *s3, double *s4, int n)
{
int mask = n-1;
double x;
double y;
int i;
int j;
for(i=0;i<n;i++){
x = 0;
y = 0;
for(j=0;j<n;j++){
x += s1[j] * s3[(i*j)&mask] - s2[j] * s4[(j*i)&mask];
y += s1[j] * s4[(i*j)&mask] + s2[j] * s3[(j*i)&mask];
}
d1[i] = x;
d2[i] = y;
}
}
void sincos_array (double *d1, double *d2, double inc, int n)
{
int i;
for(i=1;i<n;i++){
d1[i] = cos(inc*i);
d2[i] = sin(inc*i);
}
}
void complex_mult (double *d1, double *d2, double *s1, double *s2,
double *s3, double *s4, int n)
{
int i;
for(i=0;i<n;i++){
d1[i] = s1[i] * s3[i] - s2[i] * s4[i];
d2[i] = s1[i] * s4[i] + s2[i] * s3[i];
}
}
void complex_normalize (double *i1, double *i2, int n)
{
int i;
double x;
for(i=0;i<n;i++){
x = sqrt(i1[i]*i1[i] + i2[i]*i2[i]);
if (x > 0) x = 1/x;
i1[i] *= x;
i2[i] *= x;
}
}
#define N 256
int main (int argc, char *argv[])
{
double s[N], c[N];
double image1[N];
double image2[N];
double ft1r[N];
double ft1i[N];
double ft2r[N];
double ft2i[N];
double conv_r[N], conv_i[N];
double resr[N], resi[N];
int i;
sincos_array (c, s, 2*M_PI/N, N);
for(i=0;i<N;i++){
image1[i] = rand_f64();
image2[i] = 0;
}
for(i=0;i<N/2;i++){
image2[i] = image1[i+N/4+N/16];
}
discrete_fourier_transform (ft1r, ft1i, image1, c, s, N);
discrete_fourier_transform (ft2r, ft2i, image2, c, s, N);
for(i=0;i<N;i++){
ft2i[i] = -ft2i[i];
}
complex_mult (conv_r, conv_i, ft1r, ft1i, ft2r, ft2i, N);
complex_normalize (conv_r, conv_i, N);
complex_discrete_fourier_transform (resi, resr, conv_i, conv_r, c, s, N);
for(i=0;i<N;i++){
printf("%d %g %g %g %g\n", i, resr[i], resi[i], conv_r[i], conv_i[i]);
}
return 0;
}
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