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/**
* Generate random numbers that can be used by other components. We
* convert to different types/distributions elsewhere. This just
* delivers a clean, random bitvector.
*
* $Id: SCA_RandomNumberGenerator.cpp 20362 2009-05-23 14:46:43Z ben2610 $
*/
/* A C-program for MT19937: Real number version */
/* genrand() generates one pseudorandom real number (double) */
/* which is uniformly distributed on [0,1]-interval, for each */
/* call. sgenrand(seed) set initial values to the working area */
/* of 624 words. Before genrand(), sgenrand(seed) must be */
/* called once. (seed is any 32-bit integer except for 0). */
/* Integer generator is obtained by modifying two lines. */
/* Coded by Takuji Nishimura, considering the suggestions by */
/* Topher Cooper and Marc Rieffel in July-Aug. 1997. */
/* This library is free software; you can redistribute it and/or */
/* modify it under the terms of the GNU Library General Public */
/* License as published by the Free Software Foundation; either */
/* version 2 of the License, or (at your option) any later */
/* version. */
/* This library 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 Library General Public License for more details. */
/* You should have received a copy of the GNU Library General */
/* Public License along with this library; if not, write to the */
/* Free Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA */
/* 02111-1307 USA */
/* Copyright (C) 1997 Makoto Matsumoto and Takuji Nishimura. */
/* When you use this, send an email to: matumoto@math.keio.ac.jp */
/* with an appropriate reference to your work. */
#include <limits.h>
#include "SCA_RandomNumberGenerator.h"
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
/* Period parameters */
#define N 624
#define M 397
#define MATRIX_A 0x9908b0df /* constant vector a */
#define UPPER_MASK 0x80000000 /* most significant w-r bits */
#define LOWER_MASK 0x7fffffff /* least significant r bits */
/* Tempering parameters */
#define TEMPERING_MASK_B 0x9d2c5680
#define TEMPERING_MASK_C 0xefc60000
#define TEMPERING_SHIFT_U(y) (y >> 11)
#define TEMPERING_SHIFT_S(y) (y << 7)
#define TEMPERING_SHIFT_T(y) (y << 15)
#define TEMPERING_SHIFT_L(y) (y >> 18)
SCA_RandomNumberGenerator::SCA_RandomNumberGenerator(long seed) {
// int mti = N + 1; /*unused*/
m_seed = seed;
m_refcount = 1;
SetStartVector();
}
SCA_RandomNumberGenerator::~SCA_RandomNumberGenerator() {
/* intentionally empty */
}
void SCA_RandomNumberGenerator::SetStartVector(void) {
/* setting initial seeds to mt[N] using */
/* the generator Line 25 of Table 1 in */
/* [KNUTH 1981, The Art of Computer Programming */
/* Vol. 2 (2nd Ed.), pp102] */
mt[0] = m_seed & 0xffffffff;
for (mti = 1; mti < N; mti++)
mt[mti] = (69069 * mt[mti-1]) & 0xffffffff;
}
long SCA_RandomNumberGenerator::GetSeed() { return m_seed; }
void SCA_RandomNumberGenerator::SetSeed(long newseed)
{
m_seed = newseed;
SetStartVector();
}
/**
* This is the important part: copied verbatim :)
*/
unsigned long SCA_RandomNumberGenerator::Draw() {
static unsigned long mag01[2] = { 0x0, MATRIX_A };
/* mag01[x] = x * MATRIX_A for x=0,1 */
unsigned long y;
if (mti >= N) { /* generate N words at one time */
int kk;
/* I set this in the constructor, so it is always satisfied ! */
// if (mti == N+1) /* if sgenrand() has not been called, */
// GEN_srand(4357); /* a default initial seed is used */
for (kk = 0; kk < N - M; kk++) {
y = (mt[kk] & UPPER_MASK) | (mt[kk+1] & LOWER_MASK);
mt[kk] = mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1];
}
for (; kk < N-1; kk++) {
y = (mt[kk] & UPPER_MASK) | (mt[kk+1] & LOWER_MASK);
mt[kk] = mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1];
}
y = (mt[N-1] & UPPER_MASK) | (mt[0] & LOWER_MASK);
mt[N-1] = mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1];
mti = 0;
}
y = mt[mti++];
y ^= TEMPERING_SHIFT_U(y);
y ^= TEMPERING_SHIFT_S(y) & TEMPERING_MASK_B;
y ^= TEMPERING_SHIFT_T(y) & TEMPERING_MASK_C;
y ^= TEMPERING_SHIFT_L(y);
return y;
}
float SCA_RandomNumberGenerator::DrawFloat() {
return ( (float) Draw()/ (unsigned long) 0xffffffff );
}
/* eof */
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