Uladzimir Karpenka
9960a1d0e3
The tap loop wrapped the ring with a test on every tap:
if ((idx_out = idx_in + j) >= ringsize) idx_out -= ringsize;
which made the address non-affine and stopped the vectorizer. Split the
walk at the wrap point instead, so both halves are unit-stride, and split
the complex ring into separate I/Q arrays so the taps load contiguously
rather than through a de-interleaving ld2.
The dot product also could not be vectorized as written: reassociating an
fp reduction needs -ffast-math, which this library must not enable (it
relies on IEEE semantics for 0/0 = NaN and x/0 = Inf, see linux_port.h).
Carry four independent accumulator pairs instead, which both breaks the
FMA dependency chain and lets the vectorizer in on any compiler.
Measured on an Apple M1 Pro, 512-sample DSP buffers, best of 5:
xresample, decimation to 48 kHz before after speedup
192k -> 48k (561 taps) 342.0 us 84.2 us 4.06x
384k -> 48k (1121 taps) 708.9 us 175.1 us 4.05x
576k -> 48k (1681 taps) 1074.4 us 266.9 us 4.03x
768k -> 48k (2241 taps) 1438.9 us 360.0 us 4.00x
full xrxa() chain, 576k input 1148.2 us 337.6 us 3.40x
10.76% 3.16% of one core
xresampleF (float, host audio) 2.6x - 3.4x
Summation order changes, so the double path is not bit-identical: over
400 buffers of the full RX chain the worst deviation is 1.1e-12, an SNR
of 251 dB. The float path is bit-identical, as the cast to float absorbs
the difference. With the resampler bypassed (48k in, 48k out) the chain
is unchanged bit-for-bit.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
123 lines
3.8 KiB
C
123 lines
3.8 KiB
C
/* resample.h
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This file is part of a program that implements a Software-Defined Radio.
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Copyright (C) 2013 Warren Pratt, NR0V
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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The author can be reached by email at
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warren@wpratt.com
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*/
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/************************************************************************************************
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* *
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* VERSION FOR COMPLEX DOUBLE-PRECISION *
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* *
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************************************************************************************************/
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#ifndef _resample_h
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#define _resample_h
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typedef struct _resample
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{
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int run; // run
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int size; // number of input samples per buffer
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double* in; // input buffer for resampler
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double* out; // output buffer for resampler
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int in_rate;
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int out_rate;
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double fcin;
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double fc;
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double fc_low;
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double gain;
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int idx_in; // index for input into ring
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int ncoefin;
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int ncoef; // number of coefficients
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int L; // interpolation factor
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int M; // decimation factor
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double* h; // coefficients
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int ringsize; // number of complex pairs the ring buffer holds
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double* ringI; // ring buffer, in-phase
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double* ringQ; // ring buffer, quadrature (split from I so the tap loop
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// reads unit-stride and vectorizes)
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int cpp; // coefficients of the phase
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int phnum; // phase number
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} resample, *RESAMPLE;
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__declspec (dllexport)
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RESAMPLE create_resample (int run, int size, double* in, double* out, int in_rate, int out_rate, double fc, int ncoef, double gain);
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__declspec (dllexport)
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void destroy_resample (RESAMPLE a);
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__declspec (dllexport)
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void flush_resample (RESAMPLE a);
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__declspec (dllexport)
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int xresample (RESAMPLE a);
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extern void setBuffers_resample (RESAMPLE a, double* in, double* out);
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extern void setSize_resample(RESAMPLE a, int size);
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extern void setInRate_resample(RESAMPLE a, int rate);
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extern void setOutRate_resample(RESAMPLE a, int rate);
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extern void setFCLow_resample (RESAMPLE a, double fc_low);
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extern void setBandwidth_resample (RESAMPLE a, double fc_low, double fc_high);
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#endif
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/************************************************************************************************
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* *
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* VERSION FOR NON-COMPLEX FLOATS *
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* *
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************************************************************************************************/
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#ifndef _resampleF_h
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#define _resampleF_h
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typedef struct _resampleF
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{
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int run; // run
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int size; // number of input samples per buffer
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float* in; // input buffer for resampler
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float* out; // output buffer for resampler
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int idx_in; // index for input into ring
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int ncoef; // number of coefficients
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int L; // interpolation factor
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int M; // decimation factor
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double* h; // coefficients
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int ringsize; // number of values the ring buffer holds
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double* ring; // ring buffer
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int cpp; // coefficients of the phase
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int phnum; // phase number
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} resampleF, *RESAMPLEF;
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extern RESAMPLEF create_resampleF (int run, int size, float* in, float* out, int in_rate, int out_rate);
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extern void destroy_resampleF (RESAMPLEF a);
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extern void flush_resampleF (RESAMPLEF a);
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extern int xresampleF (RESAMPLEF a);
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#endif
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