mirror/kissfft
1
0
Fork 0
mirror of https://github.com/mborgerding/kissfft.git synced 2025-10-31 08:14:41 -04:00
Code Issues Packages Projects Releases Wiki Activity

broken

Browse Source 
working towards mixed radix
decomposition seems to work (for 2)
indices scrambled
This commit is contained in:
Mark Borgerding
2003-08-16 23:40:14 +00:00
parent c9ff98b2c9
commit 502211bc6a
3 changed files with 97 additions and 47 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
Makefile
View File

@ -2,7 +2,7 @@ message:
@echo "Nothing to make here. Move on down to sample_code for ... you guessed it! Sample Code!"
tarball: clean
tar -czf kiss_fft.tar.gz .
tar --exclude CVS -czf kiss_fft.tar.gz .
clean:
cd sample_code && make clean

126
kiss_fft.c
View File

@ -13,6 +13,7 @@ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
*/
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include "kiss_fft.h"
/*
@ -26,10 +27,19 @@ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
*/
typedef struct {
int nfft;
kiss_fft_cpx* twiddle;
int * swap_indices;
int nswap;
int nr; // N remaining
int radix; // radix of the stage
kiss_fft_cpx * twiddle;
}kiss_fft_stage;
#define MAX_STAGES 20
typedef struct {
int nstages;
int allocsize;
kiss_fft_stage stages[MAX_STAGES];
int * unscramble_indices;
}kiss_fft_state;
#ifdef FIXED_POINT
@ -73,20 +83,15 @@ typedef struct {
// create the twiddle factors
static
void make_twiddles(kiss_fft_cpx * twiddle,int nfft,int inverse_fft)
void make_twiddles(kiss_fft_cpx * twiddle,int ntwid,int symmetry,int inverse_fft)
{
const double pi=3.14159265358979323846264338327;
int n;
for (n=0;n< (nfft>>1);++n) {
#ifdef FIXED_POINT
// TODO: find another way to calculate these without so much floating point math
twiddle[n].r = (kiss_fft_scalar)(TWIDDLE_RANGE*cos(2*pi*n/nfft)+.5);
twiddle[n].i = -(kiss_fft_scalar)(TWIDDLE_RANGE*sin(2*pi*n/nfft)+.5);
#else
twiddle[n].r = cos(2*pi*n/nfft);
twiddle[n].i = -sin(2*pi*n/nfft);
#endif
int denom = ntwid*symmetry;
for (n=0;n<ntwid;++n) {
twiddle[n].r = cos(2*pi*n/denom);
twiddle[n].i = -sin(2*pi*n/denom);
// inverse fft uses complex conjugate twiddle factors
if (inverse_fft)
twiddle[n].i *= -1;
@ -141,32 +146,59 @@ void undo_bit_rev( kiss_fft_cpx * f, const int * swap_indices,int nswap)
// the heart of the fft
static
void fft_work(int N,kiss_fft_cpx *f,const kiss_fft_cpx * twid,int twid_step)
static
void fft_work( kiss_fft_cpx * f,const kiss_fft_stage * stage , int nstages )
{
N >>= 1;
int n;
// only works for 2s
{ // declare automatic variables in here to reduce stack usage
int n;
kiss_fft_cpx csum,cdiff;
const kiss_fft_cpx * cur_twid = twid;
kiss_fft_cpx *f1 = f;
kiss_fft_cpx *f2 = f+N;
for (n=0;n<N;++n)
kiss_fft_cpx *f2 = f+ stage->nr;
const kiss_fft_cpx * twid = stage->twiddle;
for ( n = 0 ; n < stage->nr ; ++n )
{
C_ADD( csum, *f1 , *f2 );
C_SUB( cdiff, *f1 , *f2 );
*f1++ = csum;
C_MUL(*f2, cdiff, *cur_twid);
C_MUL(*f2, cdiff, *twid);
++f2;
cur_twid += twid_step;
++twid;
}
}
if (N==1) return;
//twid_step *= 2;
fft_work(N,f+N,twid,twid_step*2);
fft_work(N,f,twid,twid_step*2);
if ( nstages == 1 )
return;
for (n=0;n<stage->radix;++n)
fft_work( f + n * stage->nr ,stage+1,nstages-1);
}
static
kiss_fft_state * decompose( kiss_fft_state * st, int * pnfft,int radix,int inverse_fft)
{
int nfft = *pnfft;
while (nfft>1 && (nfft%radix)==0) {
int newsize;
int nstages=st->nstages;
nfft /= radix;
fprintf(stderr,"%d ",radix);
newsize = st->allocsize + nfft * sizeof(kiss_fft_cpx);
st=(kiss_fft_state*)realloc(st,newsize);
st->stages[nstages].radix=radix;
st->stages[nstages].nr=nfft;
st->stages[nstages].twiddle = (kiss_fft_cpx*)((char*)st + st->allocsize);
make_twiddles( st->stages[nstages].twiddle,nfft,radix,inverse_fft );
st->allocsize = newsize;
st->nstages = nstages+1;
}
*pnfft = nfft;
return st;
}
/*
* void * kiss_fft_alloc(int nfft,int inverse_fft)
@ -179,26 +211,36 @@ void fft_work(int N,kiss_fft_cpx *f,const kiss_fft_cpx * twid,int twid_step)
void * kiss_fft_alloc(int nfft,int inverse_fft)
{
kiss_fft_state * st=NULL;
// allocate one large buffer to hold the state, twiddle buffers, and bit-rev indices
int size = sizeof(kiss_fft_state) + (nfft>>1)*sizeof(kiss_fft_cpx) + nfft*sizeof(int);
int tmp;
int i;
int allocsize=sizeof(kiss_fft_state) + nfft*sizeof(int);
st = ( kiss_fft_state *)malloc(size);
if (st) {
st->twiddle = (kiss_fft_cpx*)(st+1); // pointer just beyond the kiss_fft_state struct
st->swap_indices = (int*)( st->twiddle + (nfft>>1) );// pointer just beyond the twiddle buffer
st->nfft = nfft;
// initialize the twiddle factors
make_twiddles(st->twiddle,nfft,inverse_fft);
// create list of index-swaps
st->nswap = make_bit_reverse_indices(st->swap_indices,nfft);
st = ( kiss_fft_state *)malloc( allocsize );
st->nstages=0;
st->allocsize=allocsize;
st->unscramble_indices = (int*)(st+1);// just past end of buffer
for (i=0;i<nfft;++i)
st->unscramble_indices[i] = i;
fprintf(stderr,"factoring %d: ",nfft);
tmp=nfft;
st = decompose( st,&tmp,2,inverse_fft);
fprintf(stderr,"\n");
// TODO factor 3,5,7,11 ???
if ( tmp > 1 ) {
fprintf(stderr,"%d not factorable by 2,3 (%d remaining)\n",nfft,tmp);
free(st);
return NULL;
}
return st;
}
void kiss_fft(const void * cfg,kiss_fft_cpx *f)
{
const kiss_fft_state * st = cfg;
fft_work(st->nfft, f, st->twiddle , 1 );
undo_bit_rev(f,st->swap_indices,st->nswap);
fft_work( f, st->stages , st->nstages );
}

16
tools/fftutil.c
View File

@ -26,7 +26,7 @@ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
void fft_file(FILE * fin,FILE * fout,int nfft,int isinverse)
void fft_file(FILE * fin,FILE * fout,int nfft,int isinverse,int useascii)
{
void *st;
kiss_fft_cpx * buf;
@ -36,7 +36,13 @@ void fft_file(FILE * fin,FILE * fout,int nfft,int isinverse)
while ( fread( buf , sizeof(kiss_fft_cpx) * nfft ,1, fin ) > 0 ) {
kiss_fft( st , buf );
fwrite( buf , sizeof(kiss_fft_cpx) , nfft , fout );
if (useascii) {
int i;
for (i=0;i<nfft;++i)
fprintf(fout, "(%g,%g) ", (double)buf[i].r,(double)buf[i].i);
}else{
fwrite( buf , sizeof(kiss_fft_cpx) , nfft , fout );
}
}
free(st);
free(buf);
@ -48,11 +54,13 @@ int main(int argc,char ** argv)
int isinverse=0;
FILE *fin=stdin;
FILE *fout=stdout;
int useascii=0;
while (1) {
int c=getopt(argc,argv,"n:i");
int c=getopt(argc,argv,"n:ia");
if (c==-1) break;
switch (c) {
case 'a':useascii=1;break;
case 'n':nfft = atoi(optarg);break;
case 'i':isinverse=1;break;
}
@ -70,7 +78,7 @@ int main(int argc,char ** argv)
++optind;
}
fft_file(fin,fout,nfft,isinverse);
fft_file(fin,fout,nfft,isinverse,useascii);
if (fout!=stdout) fclose(fout);
if (fin!=stdin) fclose(fin);