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added windowing functions #61

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@hayguen hayguen commented Apr 10, 2022

for calculation of a spectrum, to be displayed,
usually a windowing is applied in time domain before calling fft() ..

c++ wrappers for windowing and complex options for the benchmark

Signed-off-by: hayati ayguen <[email protected]>
@hayguen hayguen requested review from marton78 and unevens April 10, 2022 14:08


#ifdef __cplusplus
}
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this } probably doesn't belong here?

{
case pf_winRect:
break;
default: assert(0);
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is it permitted that the default case is not at the end? i have never seen it before. even if it is, i suggest moving it to the end as it's surprising otherwise.

Comment on lines +210 to +216
// pre-calculate small trig table - hope this allow SIMD parallelization
freal2 *trig_tab = wp.trig_tab;
const freal phi_inc = TWO_PI / wp.N_div;
const freal c_inc_cos = rcos(phi_inc);
const freal c_inc_sin = rsin(phi_inc);
freal cos_phi = trig_tab[0][0] = c1;
freal sin_phi = trig_tab[0][1] = c0;
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The original PFFFT Author Julien Pommier also wrote some fast SIMD functions for sin / cos / exp / log, based on Cephes. You could consider using them, but probably this is not time sensitive code.

https://github.com/RJVB/sse_mathfun


const struct pf_windowing_param_tag * pf_window_alloc(pf_windowing_T win, int N, int w0, freal alpha)
{
struct pf_windowing_param_tag * param = new pf_windowing_param_t();
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Doesn't gcc warn about using new in C instead of malloc? Well, it should.


void pf_window_free(const struct pf_windowing_param_tag * param)
{
delete param;
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same here, this should be free.

pafWin[n] *= a0;
}
break;
default: assert(0);
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to the end please

}
}
break;
default: assert(0);
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same

Comment on lines +479 to +481
const freal mag = rsqrt(cos_phi0 * cos_phi0 + sin_phi0 * sin_phi0);
cos_phi0 /= mag;
sin_phi0 /= mag;
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Suggested change
const freal mag = rsqrt(cos_phi0 * cos_phi0 + sin_phi0 * sin_phi0);
cos_phi0 /= mag;
sin_phi0 /= mag;
const freal inv_mag = 1.0f/rsqrt(cos_phi0 * cos_phi0 + sin_phi0 * sin_phi0);
cos_phi0 *= inv_mag;
sin_phi0 *= inv_mag;

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... if only C had a built-in for inverse square roots.

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2 participants