From 2754fe8ba5519026d51af0edd2f0d05c6edfd84c Mon Sep 17 00:00:00 2001 From: Michael Niedermayer Date: Mon, 28 Jul 2008 15:35:04 +0000 Subject: Simple lagged fibonacci PRNG. 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/trunk --- libavutil/lfg.h | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) create mode 100644 libavutil/lfg.h (limited to 'libavutil/lfg.h') diff --git a/libavutil/lfg.h b/libavutil/lfg.h new file mode 100644 index 0000000000..0882faab02 --- /dev/null +++ b/libavutil/lfg.h @@ -0,0 +1,37 @@ +/* + * Lagged Fibonacci PRNG + * Copyright (c) 2008 Michael Niedermayer + * + * This file is part of FFmpeg. + * + * FFmpeg is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * FFmpeg is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with FFmpeg; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#ifndef FFMPEG_LFG_H +#define FFMPEG_LFG_H + +typedef struct { + unsigned int state[64]; + int index; +} AVLFG; + +void av_lfg_init(AVLFG *c, unsigned int seed); + +static inline unsigned int av_lfg_get(AVLFG *c){ + c->state[c->index & 63] = c->state[(c->index-24) & 63] + c->state[(c->index-55) & 63]; + return c->state[c->index++ & 63]; +} + +#endif //FFMPEG_LFG_H -- cgit v1.2.3