mirror of https://github.com/FFmpeg/FFmpeg.git
3.5 times faster than our mersene twister. 10 times less memory needed. (=less cache trashing) Originally committed as revision 14458 to svn://svn.ffmpeg.org/ffmpeg/trunkpull/126/head
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/*
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* Lagged Fibonacci PRNG |
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* Copyright (c) 2008 Michael Niedermayer |
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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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#include <inttypes.h> |
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#include "lfg.h" |
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#include "md5.h" |
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#include "intreadwrite.h" |
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void av_cold av_lfg_init(AVLFG *c, unsigned int seed){ |
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uint8_t tmp[16]={0}; |
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int i; |
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for(i=8; i<64; i+=4){ |
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AV_WL32(tmp, seed); tmp[4]=i; |
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av_md5_sum(tmp, tmp, 16); |
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c->state[i ]= AV_RL32(tmp); |
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c->state[i+1]= AV_RL32(tmp+4); |
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c->state[i+2]= AV_RL32(tmp+8); |
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c->state[i+3]= AV_RL32(tmp+12); |
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} |
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c->index=0; |
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} |
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#ifdef TEST |
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#include "log.h" |
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#include "common.h" |
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int main(void) |
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{ |
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int x=0; |
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int i, j; |
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AVLFG state; |
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av_lfg_init(&state, 0xdeadbeef); |
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for (j = 0; j < 10000; j++) { |
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START_TIMER |
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for (i = 0; i < 624; i++) { |
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// av_log(NULL,AV_LOG_ERROR, "%X\n", av_lfg_get(&state));
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x+=av_lfg_get(&state); |
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} |
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STOP_TIMER("624 calls of av_random"); |
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} |
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av_log(NULL, AV_LOG_ERROR, "final value:%X\n", x); |
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return 0; |
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} |
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#endif |
@ -0,0 +1,37 @@ |
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/*
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* Lagged Fibonacci PRNG |
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* Copyright (c) 2008 Michael Niedermayer |
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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 FFMPEG_LFG_H |
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#define FFMPEG_LFG_H |
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typedef struct { |
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unsigned int state[64]; |
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int index; |
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} AVLFG; |
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void av_lfg_init(AVLFG *c, unsigned int seed); |
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static inline unsigned int av_lfg_get(AVLFG *c){ |
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c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63]; |
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return c->state[c->index++ & 63]; |
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} |
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#endif //FFMPEG_LFG_H
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