#include "kiss_fftr.h"#include "_kiss_fft_guts.h"#include <sys/times.h>#include <time.h>#include <unistd.h>static double cputime(void){    struct tms t;    times(&t);    return (double)(t.tms_utime + t.tms_stime)/  sysconf(_SC_CLK_TCK) ;}staticdouble snr_compare( kiss_fft_cpx * vec1,kiss_fft_cpx * vec2, int n){    int k;    double sigpow,noisepow,err,snr,scale=0;    sigpow = noisepow = .00000000000000000001;     for (k=0;k<n;++k) {        sigpow += (double)vec1[k].r * (double)vec1[k].r +                   (double)vec1[k].i * (double)vec1[k].i;        err = (double)vec1[k].r - (double)vec2[k].r;        noisepow += err * err;        err = (double)vec1[k].i - (double)vec2[k].i;        noisepow += err * err;        if (vec1[k].r)            scale +=(double) vec2[k].r / (double)vec1[k].r;        /*        fprintf(stderr,"vec1=");pcpx(vec1+k);        fprintf(stderr,"vec2=");pcpx(vec2+k);        */    }    snr = 10*log10( sigpow / noisepow );    scale /= n;    if (snr<10) {        printf( "\npoor snr, try a scaling factor %f\n" , scale );        exit(1);    }    return snr;}#define RANDOM#ifndef RANDOM#define NFFT 8#else#define NFFT 8*3*5#endif#ifndef NUMFFTS#define NUMFFTS 1000#endifint main(void){    double ts,tfft,trfft;    int i;    kiss_fft_cpx cin[NFFT];    kiss_fft_scalar rin[NFFT] = {0.309655,0.815653,0.768570,0.591841,0.404767,0.637617,0.007803,0.012665};    kiss_fft_cpx cout[NFFT];    kiss_fft_cpx sout[NFFT];        kiss_fft_cfg  kiss_fft_state;    kiss_fftr_cfg  kiss_fftr_state;        srand(time(0));    for (i=0;i<NFFT;++i) {#ifdef RANDOM                rin[i] = (kiss_fft_scalar)(rand()-RAND_MAX/2);#endif                cin[i].r = rin[i];        cin[i].i = 0;    }    kiss_fft_state = kiss_fft_alloc(NFFT,0,0,0);    kiss_fftr_state = kiss_fftr_alloc(NFFT,0,0,0);    kiss_fft(kiss_fft_state,cin,cout);    kiss_fftr(kiss_fftr_state,rin,sout);    printf( "nfft=%d, inverse=%d, snr=%g\n",            NFFT,0, snr_compare(cout,sout,(NFFT/2)+1) );#ifdef RANDOM            ts = cputime();    for (i=0;i<NUMFFTS;++i) {        kiss_fft(kiss_fft_state,cin,cout);    }    tfft = cputime() - ts;        ts = cputime();    for (i=0;i<NUMFFTS;++i) {        kiss_fftr( kiss_fftr_state, rin, cout );        /* kiss_fftri(kiss_fftr_state,cout,rin); */    }    trfft = cputime() - ts;    printf("%d complex ffts took %gs, real took %gs\n",NUMFFTS,tfft,trfft);#endif            free(kiss_fft_state);    free(kiss_fftr_state);    kiss_fft_state = kiss_fft_alloc(NFFT,1,0,0);    kiss_fftr_state = kiss_fftr_alloc(NFFT,1,0,0);    kiss_fft(kiss_fft_state,cout,cin);    kiss_fftri(kiss_fftr_state,cout,rin);    for (i=0;i<NFFT;++i) {        sout[i].r = rin[i];        sout[i].i = 0;    }        printf( "nfft=%d, inverse=%d, snr=%g\n",            NFFT,1, snr_compare(cin,cin,NFFT/2) );    free(kiss_fft_state);    free(kiss_fftr_state);    return 0;}