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https://github.com/mborgerding/kissfft.git
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radix 4 works but slow
This commit is contained in:
Mark Borgerding
parent
6b76490456
commit
2ae7e0f1f2
141
kiss_fft.c
141
kiss_fft.c
@ -73,6 +73,7 @@ kiss_fft_cpx cexp(double phase)
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return x;
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}
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static
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void fft_work(
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kiss_fft_cpx * Fout,
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@ -82,6 +83,80 @@ void fft_work(
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const kiss_fft_state * st
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);
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static
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void fft4work(
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kiss_fft_cpx * Fout,
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const kiss_fft_cpx * f,
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int fstride,
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int * factors,
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const kiss_fft_state * st
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)
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{
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kiss_fft_cpx * Fout1;
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kiss_fft_cpx * Fout2;
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kiss_fft_cpx * Fout3;
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int m,q,u,k;
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kiss_fft_cpx t;
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kiss_fft_cpx * scratch = st->scratch;
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kiss_fft_cpx * twiddles = st->twiddles;
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int Norig = st->nfft;
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factors++;
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m=*factors++;
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Fout1 = Fout + m;
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Fout2 = Fout + 2*m;
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Fout3 = Fout + 3*m;
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if (m==1) {
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Fout[0] = f[0];
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Fout[1] = f[fstride*1];
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Fout[2] = f[fstride*2];
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Fout[3] = f[fstride*3];
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}else{
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fft_work( Fout , f, fstride*4,factors,st);
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fft_work( Fout1 ,f+fstride, fstride*4,factors,st);
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fft_work( Fout2 ,f+fstride*2, fstride*4,factors,st);
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fft_work( Fout3 ,f+fstride*3, fstride*4,factors,st);
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}
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for ( u=0; u<m; ++u ) {
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int twidx;
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scratch[0]= *Fout;
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scratch[1]= *Fout1;
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scratch[2]= *Fout2;
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scratch[3]= *Fout3;
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k=u;
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*Fout = scratch[0];
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*Fout1 = scratch[0];
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*Fout2 = scratch[0];
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*Fout3 = scratch[0];
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for (q=1;q<4;++q ) {
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twidx = (fstride * (u+0*m) * q)%Norig;
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C_MUL(t,scratch[q] , twiddles[twidx] );
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C_ADDTO(*Fout,t);
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twidx = (fstride * (u+1*m) * q)%Norig;
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C_MUL(t,scratch[q] , twiddles[twidx] );
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C_ADDTO(*Fout1,t);
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twidx = (fstride * (u+2*m) * q)%Norig;
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C_MUL(t,scratch[q] , twiddles[twidx] );
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C_ADDTO(*Fout2,t);
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twidx = (fstride * (u+3*m) * q)%Norig;
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C_MUL(t,scratch[q] , twiddles[twidx] );
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C_ADDTO(*Fout3,t);
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}
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++Fout;
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++Fout1;
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++Fout2;
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++Fout3;
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}
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}
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// the heart of the fft
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static
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void fft2work(
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@ -92,36 +167,39 @@ void fft2work(
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const kiss_fft_state * st
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)
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{
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int m;
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kiss_fft_cpx * Fout2;
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int u,m;
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kiss_fft_cpx t;
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kiss_fft_cpx * twiddles = st->twiddles;
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factors++;// p==2
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factors++;
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m=*factors++;
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Fout2 = Fout + m;
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if (*factors == 2){
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fft2work(Fout,f,fstride*2,factors,st);
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fft2work(Fout+m,f+fstride,fstride*2,factors,st);
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}else if (m==1) {
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if (m==1) {
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Fout[0] = f[0];
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Fout[1] = f[fstride];
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} else if (*factors == 2) {
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fft2work(Fout,f,fstride*2,factors,st);
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fft2work(Fout2,f+fstride,fstride*2,factors,st);
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} else {
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fft_work( Fout , f, fstride*2,factors,st);
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fft_work( Fout + m, f+fstride, fstride*2,factors,st);
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}
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Fout2 = Fout + m;
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for ( u=0; u<m; ++u ) {
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C_MUL (t, *Fout2 , *twiddles);
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twiddles += fstride;
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C_SUB( *Fout2 , *Fout , t );
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C_ADDTO( *Fout , t );
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++Fout2;
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++Fout;
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{
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kiss_fft_cpx * twiddles = st->twiddles;
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kiss_fft_cpx t;
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do{
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C_MUL (t, *Fout2 , *twiddles);
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twiddles += fstride;
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C_SUB( *Fout2 , *Fout , t );
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C_ADDTO( *Fout , t );
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++Fout2;
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++Fout;
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}while (--m);
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}
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}
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static
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void fft_work(
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kiss_fft_cpx * Fout,
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@ -135,13 +213,11 @@ void fft_work(
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kiss_fft_cpx t;
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kiss_fft_cpx * scratch = st->scratch;
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kiss_fft_cpx * twiddles = st->twiddles;
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int Norig = st->nfft;
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#if 1
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switch (*factors) {
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case 2:
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fft2work(Fout,f,fstride,factors,st);
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return;
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case 4: fft4work(Fout,f,fstride,factors,st); return;
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case 2: fft2work(Fout,f,fstride,factors,st); return;
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default:
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break;
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}
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@ -173,9 +249,9 @@ void fft_work(
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int twidx=0;
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Fout[ k ] = scratch[0];
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for (q=1;q<p;++q ) {
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int Norig = st->nfft;
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twidx += fstride * k;
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if (twidx>=Norig)
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twidx-=Norig;
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if (twidx>=Norig) twidx-=Norig;
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C_MUL(t,scratch[q] , twiddles[twidx] );
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Fout[ k ].r += t.r;
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Fout[ k ].i += t.i;
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@ -227,7 +303,7 @@ void * kiss_fft_alloc(int nfft,int inverse_fft)
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}
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while (nfft>1) {
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const int primes[] = {2,3,5,7,11,13,17,-1};
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const int primes[] = {4,2,3,5,7,11,13,17,-1};
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int p=nfft;
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i=0;
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while ( primes[i] != -1 ) {
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@ -240,8 +316,27 @@ void * kiss_fft_alloc(int nfft,int inverse_fft)
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st->factors[2*nstages] = p;
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nfft /= p;
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st->factors[2*nstages+1] = nfft;
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//printf("%d,%d ",p,nfft);
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++nstages;
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}
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//printf("\n");
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// reverse the factors list so that the 2s are packed to the back
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nfft=st->nfft;
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for ( i=0 ; i< nstages ;i+=2 ) {
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int p;
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p = st->factors[i];
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st->factors[i] = st->factors[ 2*nstages-i-2];
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st->factors[2*nstages-i-2 ] = p;
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}
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for ( i=0 ; i< nstages*2 ;i+=2 ) {
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nfft /= st->factors[i];
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st->factors[i+1] = nfft;
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//printf("%d,%d ",st->factors[i], st->factors[i+1] );
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}
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return st;
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}
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