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fft3.c
Go to the documentation of this file.00001 #include "mrilib.h"
00002
00003 int main( int argc , char * argv[] )
00004 {
00005 int N ;
00006 complex * cx , * cs ;
00007 int ii ;
00008 float f , sum , xx,yy ;
00009
00010 if( argc < 3 ){ printf("Usage: fft3 N nf\n"); exit(1); }
00011
00012 N = strtod( argv[1] , NULL ) ;
00013
00014 if( N > 0 && N != csfft_nextup(N) ){
00015 fprintf(stderr,"Can't do FFT of length %d\n",N) ; exit(1) ;
00016 } else if ( N < 0 ){
00017 N = -N ;
00018 }
00019
00020 f = strtod( argv[2] , NULL ) / N ;
00021
00022 cs = (complex *) malloc(sizeof(complex)*N) ;
00023 cx = (complex *) malloc(sizeof(complex)*N) ;
00024
00025 for( ii=0 ; ii < N ; ii++ ){
00026 cx[ii].r = cos(2*PI*f*ii) ; cx[ii].i = sin(2*PI*f*ii) ;
00027 cs[ii] = cx[ii] ;
00028 }
00029
00030 csfft_cox( -1 , N , cx ) ;
00031
00032 for( ii=0 ; ii < N ; ii++ )
00033 printf("%2d: %12.5g %12.5g\n" , ii , cx[ii].r , cx[ii].i ) ;
00034
00035 csfft_cox( 1 , N , cx ) ;
00036 sum = 0.0 ;
00037 for( ii=0 ; ii < N ; ii++ ){
00038 xx = cx[ii].r/N - cs[ii].r ;
00039 yy = cx[ii].i/N - cs[ii].i ; sum += xx*xx + yy*yy ;
00040 }
00041 sum = sqrt( sum/N ) ;
00042 printf("RMS error = %g\n",sum) ;
00043 exit(0) ;
00044 }
