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KissFFT: not fully legal speed optimisation (doesn't take care of inf/nan)

This commit is contained in:
Christian Daniel 2012-06-22 00:06:05 +02:00
parent 469c95f859
commit a09cf1dc95
1 changed files with 9 additions and 5 deletions
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14
dsp/kissfft.h
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@ -176,7 +176,8 @@ private:
}
void C_MUL(cpx_type& c, const cpx_type& a, const cpx_type& b)
{
c = a * b;
//c = a * b;
c = cpx_type(a.real() * b.real() - a.imag() * b.imag(), a.real() * b.imag() + a.imag() * b.real());
}
void C_SUB(cpx_type& c, const cpx_type& a, const cpx_type& b)
{
@ -205,7 +206,9 @@ private:
void kf_bfly2(cpx_type* Fout, const size_t fstride, int m)
{
for(int k = 0; k < m; ++k) {
cpx_type t = Fout[m + k] * _traits.twiddle(k * fstride);
//cpx_type t = Fout[m + k] * _traits.twiddle(k * fstride);
cpx_type t;
C_MUL(t, Fout[m + k], _traits.twiddle(k * fstride));
Fout[m + k] = Fout[k] - t;
Fout[k] += t;
}
@ -216,9 +219,10 @@ private:
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[0] = Fout[k + m] * _traits.twiddle(k * fstride);
C_MUL(scratch[0], Fout[k + m], _traits.twiddle(k * fstride));
C_MUL(scratch[1], Fout[k + 2 * m], _traits.twiddle(k * fstride * 2));
C_MUL(scratch[2], Fout[k + 3 * m], _traits.twiddle(k * fstride * 3));
scratch[5] = Fout[k] - scratch[1];
Fout[k] += scratch[1];