mirror/kissfft
1
0
Fork 0
mirror of https://github.com/mborgerding/kissfft.git synced 2025-05-27 21:20:27 -04:00
Code Issues Packages Projects Releases Wiki Activity

faster

Browse Source
This commit is contained in:
Mark Borgerding 2003-11-07 03:04:52 +00:00
parent e9095a161c
commit 1486d89291
1 changed files with 39 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

60
kiss_fft.c
View File

@ -287,45 +287,63 @@ void bfly_generic(
int p
)
{
int u,q,d;
int u,q,d,fsm,halfp,mp;
kiss_fft_cpx * scratch = st->scratch;
kiss_fft_cpx * scratch2 = scratch + p;
kiss_fft_cpx * tw = st->twiddles;
kiss_fft_cpx tlo,t1,t2,t3,t4;
kiss_fft_cpx tlo,t3,t4;
kiss_fft_cpx *Foutlo,*Fouthi;
fsm = fstride*m;
halfp=p/2;
mp=m*p;
for ( q=1; q<p ; ++q ) {
int twidx = q*fsm;
for ( d=1; d<=halfp;++d) {
tlo = tw[ twidx];
twidx += d*fsm;
if (twidx >= st->nfft)
twidx -= st->nfft;
*scratch2++ = tlo;
}
}
for ( u=0; u<m; ++u ) {
scratch[0] = Fout[u];
scratch[0] = Fout[0];
scratch2 = scratch + p;
for ( q=1 ; q<p ; ++q ) {
C_MUL( scratch[q] , Fout[ m*q + u] , tw[u*fstride*q] );
Fout[ m*q + u] = scratch[0];
C_ADDTO(Fout[u] , scratch[q] );
C_MUL( scratch[q] , Fout[ m*q ] , tw[u*fstride*q] );
Fout[ m*q ] = scratch[0];
C_ADDTO(*Fout , scratch[q] );
}
for ( q=1; q<p ; ++q ) {
int twidx = q*fstride * m;
for ( d=1; d<=p/2;++d) {
int twidx = q*fsm;
tlo = tw[ twidx];
twidx += d*fstride*m;
Foutlo=Fout;
Fouthi=Fout + mp;
if (twidx >= st->nfft)
twidx -= st->nfft;
for ( d=1; d<=halfp;++d) {
Foutlo += m;
Fouthi -= m;
tlo = *scratch2++;
t3.r = scratch[q].r * tlo.r;
t3.i = scratch[q].r * tlo.i;
t4.r = scratch[q].i * tlo.i;
t4.i = - scratch[q].i * tlo.r;
t1.r = t3.r - t4.r;
t1.i = t3.i - t4.i;
t2.r = t3.r + t4.r;
t2.i = - (t3.i + t4.i);
C_ADDTO( Fout[ m*d+u ] ,t1);
C_ADDTO( Fout[ m*(p-d)+u ] ,t2);
Foutlo->r += t3.r - t4.r;
Fouthi->r += t3.r + t4.r;
Foutlo->i += t3.i - t4.i;
Fouthi->i -= t3.i + t4.i;
}
}
++Fout;
}
}
@ -351,7 +369,7 @@ void fft_work(
switch (p) {
case 2: bfly2(Fout,fstride,st,m); break;
#if 0
#if 0
case 3: bfly3(Fout,fstride,st,m); break;
#endif
case 4: bfly4(Fout,fstride,st,m); break;