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Mark Borgerding
2009-05-18 03:23:38 +00:00
parent 3a27b71226
commit 3a4db1fed7
2 changed files with 34 additions and 53 deletions
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85
kissfft.hh
View File

@ -22,8 +22,9 @@ struct traits
std::vector<int> & stageRadix,
std::vector<int> & stageRemainder )
{
dst.resize(nfft);
fill_twiddles( &dst[0],nfft,inverse);
_twiddles.resize(nfft);
fill_twiddles( &_twiddles[0],nfft,inverse);
dst = _twiddles;
//factorize
//start factoring out 4's, then 2's, then 3,5,7,9,...
@ -44,7 +45,10 @@ struct traits
stageRemainder.push_back(n);
}while(n>1);
}
//const std::complex<T_scalar> twiddle(int i) { return _twiddle[i]; }
std::vector<cpx_type> _twiddles;
const cpx_type twiddle(int i) { return _twiddles[i]; }
};
}
@ -67,11 +71,11 @@ class kissfft
void transform(const cpx_type * src , cpx_type * dst)
{
kf_work(0, dst, src, 1);
kf_work(0, dst, src, 1,1);
}
private:
void kf_work( int stage,cpx_type * Fout, const cpx_type * f, const size_t fstride)
void kf_work( int stage,cpx_type * Fout, const cpx_type * f, size_t fstride,size_t in_stride)
{
int p = _stageRadix[stage];
int m = _stageRemainder[stage];
@ -81,7 +85,7 @@ class kissfft
if (m==1) {
do{
*Fout = *f;
f += fstride;
f += fstride*in_stride;
}while(++Fout != Fout_end );
}else{
do{
@ -89,8 +93,8 @@ class kissfft
// DFT of size m*p performed by doing
// p instances of smaller DFTs of size m,
// each one takes a decimated version of the input
kf_work(stage+1, Fout , f, fstride*p);
f += fstride;
kf_work(stage+1, Fout , f, fstride*p,in_stride);
f += fstride*in_stride;
}while( (Fout += m) != Fout_end );
}
@ -118,56 +122,33 @@ class kissfft
void kf_bfly2( cpx_type * Fout, const size_t fstride, int m)
{
cpx_type * Fout2;
cpx_type * tw1 = &_twiddles[0];
cpx_type t;
Fout2 = Fout + m;
do{
C_FIXDIV(*Fout,2); C_FIXDIV(*Fout2,2);
C_MUL (t, *Fout2 , *tw1);
tw1 += fstride;
C_SUB( *Fout2 , *Fout , t );
C_ADDTO( *Fout , t );
++Fout2;
++Fout;
}while (--m);
for (int k=0;k<m;++k) {
cpx_type t = Fout[m+k] * _traits.twiddle(k*fstride);
Fout[m+k] = Fout[k] - t;
Fout[k] += t;
}
}
void kf_bfly4( cpx_type * Fout, const size_t fstride, const size_t m)
{
cpx_type *tw1,*tw2,*tw3;
cpx_type scratch[6];
size_t k=m;
const size_t m2=2*m;
const size_t m3=3*m;
cpx_type scratch[7];
int negative_if_inverse = _inverse * -2 +1;
for (size_t k=0;k<m;++k) {
scratch[0] = Fout[k+m] * _traits.twiddle(k*fstride);
scratch[1] = Fout[k+2*m] * _traits.twiddle(k*fstride*2);
scratch[2] = Fout[k+3*m] * _traits.twiddle(k*fstride*3);
scratch[5] = Fout[k] - scratch[1];
tw3 = tw2 = tw1 = &_twiddles[0];
Fout[k] += scratch[1];
scratch[3] = scratch[0] + scratch[2];
scratch[4] = scratch[0] - scratch[2];
scratch[4] = cpx_type( scratch[4].imag()*negative_if_inverse , -scratch[4].real()* negative_if_inverse );
do {
C_MUL(scratch[0],Fout[m] , *tw1 );
C_MUL(scratch[1],Fout[m2] , *tw2 );
C_MUL(scratch[2],Fout[m3] , *tw3 );
C_SUB( scratch[5] , *Fout, scratch[1] );
C_ADDTO(*Fout, scratch[1]);
C_ADD( scratch[3] , scratch[0] , scratch[2] );
C_SUB( scratch[4] , scratch[0] , scratch[2] );
C_SUB( Fout[m2], *Fout, scratch[3] );
tw1 += fstride;
tw2 += fstride*2;
tw3 += fstride*3;
C_ADDTO( *Fout , scratch[3] );
if(_inverse) {
Fout[m] = cpx_type( scratch[5].real() - scratch[4].imag() , scratch[5].imag() + scratch[4].real() );
Fout[m3] = cpx_type( scratch[5].real() + scratch[4].imag() , scratch[5].imag() - scratch[4].real() );
}else{
Fout[m] = cpx_type( scratch[5].real() + scratch[4].imag() , scratch[5].imag() - scratch[4].real() );
Fout[m3] = cpx_type( scratch[5].real() - scratch[4].imag() , scratch[5].imag() + scratch[4].real() );
}
++Fout;
}while(--k);
Fout[k+2*m] = Fout[k] - scratch[3];
Fout[k] += scratch[3];
Fout[k+m] = scratch[5] + scratch[4];
Fout[k+3*m] = scratch[5] - scratch[4];
}
}
void kf_bfly3( cpx_type * Fout, const size_t fstride, const size_t m)

2
test/testcpp.cc
View File

@ -67,7 +67,7 @@ int main(int argc,char ** argv)
}else{
dotest<float>(32); dotest<double>(32); dotest<long double>(32);
dotest<float>(1024); dotest<double>(1024); dotest<long double>(1024);
dotest<float>(1800); dotest<double>(1800); dotest<long double>(1800);
dotest<float>(840); dotest<double>(840); dotest<long double>(840);
}
return 0;
}