test_fix_fft.c

很不错的FFT算法

/*
  Short test program to accompany fix_fft.c
*/

#define DEBUG 0

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#include "fix_fft.c"

#define N 128
#define log2N 7
#define AMPLITUDE 12288

#define MAX(a,b) (((a)>(b))?(a):(b))

int main()
{
	int i, scale;
	unsigned diff;
	short x[N], fx[N], fy[N];

	for (i=0; i<N; i++) {
		fx[i] = fy[i] = x[i] = AMPLITUDE*cos(i*2*3.1415926535/N);
#if DEBUG
			printf("%d %d\n", i, x[i]);
#endif
	}

	fix_fftr(fy, log2N, 0);
	scale = fix_fftr(fy, log2N, 1);
#if DEBUG
	puts("");
	fprintf(stderr, "scale = %d\n", scale);
#endif

	for (i=0,diff=0; i<N; i++) {
#if DEBUG
		int sample;
		sample = fy[i] << scale;
		printf("%d %d\n", i, sample);
#endif
		diff = MAX(abs(fx[i]-(fy[i] << scale)), diff);
	}
	fprintf(stderr, "max amplitude error = %g %%\n",
			diff *100./AMPLITUDE);
	return 0;
}