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07a11ebcab
This exploits an approach based on the sieve of Eratosthenes, a popular method for generating prime numbers. Tables are identical to previous ones. Tested with FATE with/without --enable-hardcoded-tables. Sample benchmark (Haswell, GNU/Linux+gcc): prev: 7860100 decicycles in cbrt_tableinit, 1 runs, 0 skips 7777490 decicycles in cbrt_tableinit, 2 runs, 0 skips [...] 7582339 decicycles in cbrt_tableinit, 256 runs, 0 skips 7563556 decicycles in cbrt_tableinit, 512 runs, 0 skips new: 2099480 decicycles in cbrt_tableinit, 1 runs, 0 skips 2044470 decicycles in cbrt_tableinit, 2 runs, 0 skips [...] 1796544 decicycles in cbrt_tableinit, 256 runs, 0 skips 1791631 decicycles in cbrt_tableinit, 512 runs, 0 skips Both small and large run count given as this is called once so small run count may give a better picture, small numbers are fairly consistent, and there is a consistent downward trend from small to large runs, at which point it stabilizes to a new value. Reviewed-by: Michael Niedermayer <michael@niedermayer.cc> Signed-off-by: Ganesh Ajjanagadde <gajjanagadde@gmail.com>
84 lines
2.4 KiB
C
84 lines
2.4 KiB
C
/*
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* Header file for hardcoded AAC cube-root table
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*
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* Copyright (c) 2010 Reimar Döffinger <Reimar.Doeffinger@gmx.de>
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg 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 GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; 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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*/
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#ifndef AVCODEC_CBRT_TABLEGEN_H
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#define AVCODEC_CBRT_TABLEGEN_H
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#include <stdint.h>
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#include <math.h>
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#include "libavutil/attributes.h"
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#include "libavutil/intfloat.h"
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#include "libavcodec/aac_defines.h"
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#if USE_FIXED
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#define CBRT(x) lrint((x) * 8192)
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#else
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#define CBRT(x) av_float2int((float)(x))
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#endif
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#if CONFIG_HARDCODED_TABLES
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#if USE_FIXED
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#define cbrt_tableinit_fixed()
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#include "libavcodec/cbrt_fixed_tables.h"
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#else
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#define cbrt_tableinit()
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#include "libavcodec/cbrt_tables.h"
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#endif
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#else
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static uint32_t cbrt_tab[1 << 13];
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static av_cold void AAC_RENAME(cbrt_tableinit)(void)
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{
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static double cbrt_tab_dbl[1 << 13];
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if (!cbrt_tab[(1<<13) - 1]) {
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int i, j, k;
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double cbrt_val;
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for (i = 1; i < 1<<13; i++)
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cbrt_tab_dbl[i] = 1;
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/* have to take care of non-squarefree numbers */
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for (i = 2; i < 90; i++) {
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if (cbrt_tab_dbl[i] == 1) {
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cbrt_val = i * cbrt(i);
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for (k = i; k < 1<<13; k *= i)
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for (j = k; j < 1<<13; j += k)
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cbrt_tab_dbl[j] *= cbrt_val;
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}
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}
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for (i = 91; i <= 8191; i+= 2) {
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if (cbrt_tab_dbl[i] == 1) {
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cbrt_val = i * cbrt(i);
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for (j = i; j < 1<<13; j += i)
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cbrt_tab_dbl[j] *= cbrt_val;
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}
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}
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for (i = 0; i < 1<<13; i++)
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cbrt_tab[i] = CBRT(cbrt_tab_dbl[i]);
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}
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}
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#endif /* CONFIG_HARDCODED_TABLES */
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#endif /* AVCODEC_CBRT_TABLEGEN_H */
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