Initial revision

source/gameengine/GameLogic/SCA_RandomNumberGenerator.cpp

@@ -0,0 +1,125 @@
+/**
+ * Generate random numbers that can be used by other components. We 
+ * convert to different types/distributions elsewhere. This just 
+ * delivers a clean, random bitvector.
+ *
+ * $Id$
+ */
+
+/* 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"
+
+/* 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;
+	m_seed = seed;
+	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 */