kf_bfly3()

static void kf_bfly3 ( kiss_fft_cpx * Fout, const size_t fstride, const kiss_fft_cfg st, size_t m )

static

Definition at line 86 of file kiss_fft.c.

{
     size_t k=m;
     const size_t m2 = 2*m;
     kiss_fft_cpx *tw1,*tw2;
     kiss_fft_cpx scratch[5];
     kiss_fft_cpx epi3;
     epi3 = st->twiddles[fstride*m];
 
     tw1=tw2=st->twiddles;
 
     do{
         C_FIXDIV(*Fout,3); C_FIXDIV(Fout[m],3); C_FIXDIV(Fout[m2],3);
 
         C_MUL(scratch[1],Fout[m] , *tw1);
         C_MUL(scratch[2],Fout[m2] , *tw2);
 
         C_ADD(scratch[3],scratch[1],scratch[2]);
         C_SUB(scratch[0],scratch[1],scratch[2]);
         tw1 += fstride;
         tw2 += fstride*2;
 
         Fout[m].r = Fout->r - HALF_OF(scratch[3].r);
         Fout[m].i = Fout->i - HALF_OF(scratch[3].i);
 
         C_MULBYSCALAR( scratch[0] , epi3.i );
 
         C_ADDTO(*Fout,scratch[3]);
 
         Fout[m2].r = Fout[m].r + scratch[0].i;
         Fout[m2].i = Fout[m].i - scratch[0].r;
 
         Fout[m].r -= scratch[0].i;
         Fout[m].i += scratch[0].r;
 
         ++Fout;
     }while(--k);
}

References C_ADD, C_ADDTO, C_FIXDIV, C_MUL, C_MULBYSCALAR, C_SUB, HALF_OF, kiss_fft_cpx::i, kiss_fft_cpx::r, and kiss_fft_state::twiddles.

Referenced by kf_work().

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