134 lines
4.4 KiB
C++
134 lines
4.4 KiB
C++
/** \file gameengine/GameLogic/SCA_RandomNumberGenerator.cpp
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* \ingroup gamelogic
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*/
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/**
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* Generate random numbers that can be used by other components. We
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* convert to different types/distributions elsewhere. This just
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* delivers a clean, random bitvector.
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*
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*/
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/* A C-program for MT19937: Real number version */
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/* genrand() generates one pseudorandom real number (double) */
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/* which is uniformly distributed on [0,1]-interval, for each */
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/* call. sgenrand(seed) set initial values to the working area */
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/* of 624 words. Before genrand(), sgenrand(seed) must be */
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/* called once. (seed is any 32-bit integer except for 0). */
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/* Integer generator is obtained by modifying two lines. */
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/* Coded by Takuji Nishimura, considering the suggestions by */
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/* Topher Cooper and Marc Rieffel in July-Aug. 1997. */
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/* This library is free software; you can redistribute it and/or */
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/* modify it under the terms of the GNU Library General Public */
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/* License as published by the Free Software Foundation; either */
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/* version 2 of the License, or (at your option) any later */
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/* version. */
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/* This library 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 Library General Public License for more details. */
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/* You should have received a copy of the GNU Library General */
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/* Public License along with this library; if not, write to the */
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/* Free Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA */
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/* 02110-1301, USA */
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/* Copyright (C) 1997 Makoto Matsumoto and Takuji Nishimura. */
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/* When you use this, send an email to: matumoto@math.keio.ac.jp */
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/* with an appropriate reference to your work. */
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#include <limits.h>
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#include "SCA_RandomNumberGenerator.h"
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/* Period parameters */
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#define N 624
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#define M 397
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#define MATRIX_A 0x9908b0df /* constant vector a */
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#define UPPER_MASK 0x80000000 /* most significant w-r bits */
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#define LOWER_MASK 0x7fffffff /* least significant r bits */
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/* Tempering parameters */
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#define TEMPERING_MASK_B 0x9d2c5680
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#define TEMPERING_MASK_C 0xefc60000
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#define TEMPERING_SHIFT_U(y) (y >> 11)
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#define TEMPERING_SHIFT_S(y) (y << 7)
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#define TEMPERING_SHIFT_T(y) (y << 15)
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#define TEMPERING_SHIFT_L(y) (y >> 18)
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SCA_RandomNumberGenerator::SCA_RandomNumberGenerator(long seed)
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{
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// int mti = N + 1; /*unused*/
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m_seed = seed;
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m_refcount = 1;
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SetStartVector();
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}
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SCA_RandomNumberGenerator::~SCA_RandomNumberGenerator()
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{
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/* intentionally empty */
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}
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void SCA_RandomNumberGenerator::SetStartVector(void)
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{
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/* setting initial seeds to mt[N] using */
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/* the generator Line 25 of Table 1 in */
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/* [KNUTH 1981, The Art of Computer Programming */
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/* Vol. 2 (2nd Ed.), pp102] */
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mt[0] = m_seed & 0xffffffff;
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for (mti = 1; mti < N; mti++)
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mt[mti] = (69069 * mt[mti-1]) & 0xffffffff;
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}
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long SCA_RandomNumberGenerator::GetSeed() { return m_seed; }
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void SCA_RandomNumberGenerator::SetSeed(long newseed)
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{
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m_seed = newseed;
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SetStartVector();
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}
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/**
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* This is the important part: copied verbatim :)
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*/
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unsigned long SCA_RandomNumberGenerator::Draw()
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{
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static unsigned long mag01[2] = { 0x0, MATRIX_A };
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/* mag01[x] = x * MATRIX_A for x=0,1 */
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unsigned long y;
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if (mti >= N) { /* generate N words at one time */
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int kk;
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/* I set this in the constructor, so it is always satisfied ! */
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// if (mti == N+1) /* if sgenrand() has not been called, */
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// GEN_srand(4357); /* a default initial seed is used */
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for (kk = 0; kk < N - M; kk++) {
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y = (mt[kk] & UPPER_MASK) | (mt[kk+1] & LOWER_MASK);
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mt[kk] = mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1];
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}
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for (; kk < N-1; kk++) {
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y = (mt[kk] & UPPER_MASK) | (mt[kk+1] & LOWER_MASK);
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mt[kk] = mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1];
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}
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y = (mt[N-1] & UPPER_MASK) | (mt[0] & LOWER_MASK);
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mt[N-1] = mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1];
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mti = 0;
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}
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y = mt[mti++];
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y ^= TEMPERING_SHIFT_U(y);
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y ^= TEMPERING_SHIFT_S(y) & TEMPERING_MASK_B;
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y ^= TEMPERING_SHIFT_T(y) & TEMPERING_MASK_C;
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y ^= TEMPERING_SHIFT_L(y);
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return y;
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}
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float SCA_RandomNumberGenerator::DrawFloat()
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{
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return ( (float) Draw()/ (unsigned long) 0xffffffff );
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}
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/* eof */
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