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mtwist_rand_0_1 produces numbers in the range [0, 1) and mtwist_rand_m1_1 produces numbers in the range (-1, 1). The numbers will not be denormal, so the distribution should be fairly uniform (as much as Mersenne Twister itself is), but this needs proper testing. 0 is included for the mtwist_rand_0_1 as it seems useful, but -1 is not included in mtwist_rand_m1_1 in order to keep the extremes of the distribution balanced around 0.
86 lines
1.8 KiB
C
86 lines
1.8 KiB
C
/*
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mersenne.h
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Mersenne Twister PRNG
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Copyright (C) 2013 Bill Currie <bill@taniwha.org>
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Author: Bill Currie <bill@taniwha.org>
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Date: 2013/01/21
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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.
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See the 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:
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Free Software Foundation, Inc.
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59 Temple Place - Suite 330
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Boston, MA 02111-1307, USA
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*/
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#ifndef __QF_mersenne_h
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#define __QF_mersenne_h
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#include "QF/qtypes.h"
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#define MT_STATE_SIZE 624
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typedef struct {
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uint32_t state[MT_STATE_SIZE];
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int index;
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} mtstate_t;
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void mtwist_seed (mtstate_t *state, uint32_t seed);
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uint32_t mtwist_rand (mtstate_t *state);
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GNU89INLINE inline float mtwist_rand_0_1 (mtstate_t *state);
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GNU89INLINE inline float mtwist_rand_m1_1 (mtstate_t *state);
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#ifndef IMPLEMENT_MTWIST_Funcs
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GNU89INLINE inline
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#else
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VISIBLE
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#endif
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float
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mtwist_rand_0_1 (mtstate_t *state)
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{
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union {
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uint32_t u;
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float f;
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} uf;
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uf.u = mtwist_rand (state) & 0x007fffff;
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uf.u |= 0x3f800000;
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return uf.f - 1.0;
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}
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#ifndef IMPLEMENT_MTWIST_Funcs
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GNU89INLINE inline
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#else
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VISIBLE
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#endif
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float
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mtwist_rand_m1_1 (mtstate_t *state)
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{
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union {
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uint32_t u;
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float f;
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} uf;
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do {
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uf.u = mtwist_rand (state) & 0x007fffff;
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} while (!uf.u);
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uf.u |= 0x40000000;
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return uf.f - 3.0;
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}
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#endif//__QF_mersenne_h
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