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+/*
+// This is the ``Mersenne Twister'' random number generator MT19937, which
+// generates pseudorandom integers uniformly distributed in 0..(2^32 - 1)
+// starting from any odd seed in 0..(2^32 - 1). This version is a recode
+// by Shawn Cokus (Cokus@math.washington.edu) on March 8, 1998 of a version by
+// Takuji Nishimura (who had suggestions from Topher Cooper and Marc Rieffel in
+// July-August 1997).
+//
+// Effectiveness of the recoding (on Goedel2.math.washington.edu, a DEC Alpha
+// running OSF/1) using GCC -O3 as a compiler: before recoding: 51.6 sec. to
+// generate 300 million random numbers; after recoding: 24.0 sec. for the same
+// (i.e., 46.5% of original time), so speed is now about 12.5 million random
+// number generations per second on this machine.
+//
+// According to the URL <http://www.math.keio.ac.jp/~matumoto/emt.html>
+// (and paraphrasing a bit in places), the Mersenne Twister is ``designed
+// with consideration of the flaws of various existing generators,'' has
+// a period of 2^19937 - 1, gives a sequence that is 623-dimensionally
+// equidistributed, and ``has passed many stringent tests, including the
+// die-hard test of G. Marsaglia and the load test of P. Hellekalek and
+// S. Wegenkittl.'' It is efficient in memory usage (typically using 2506
+// to 5012 bytes of static data, depending on data type sizes, and the code
+// is quite short as well). It generates random numbers in batches of 624
+// at a time, so the caching and pipelining of modern systems is exploited.
+// It is also divide- and mod-free.
+//
+// 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 Software Foundation, Inc., 59 Temple
+// Place, Suite 330, Boston, MA 02111-1307, USA.
+//
+// The code as Shawn received it included the following notice:
+//
+// Copyright (C) 1997 Makoto Matsumoto and Takuji Nishimura. When
+// you use this, send an e-mail to <matumoto@math.keio.ac.jp> with
+// an appropriate reference to your work.
+//
+// It would be nice to CC: <Cokus@math.washington.edu> when you write.
+//
+*/
+
+#include <time.h>
+#include "mt_rand.h"
+
+#define N (624) /* length of state vector */
+#define M (397) /* a period parameter */
+#define K (0x9908B0DFU) /* a magic constant */
+#define hiBit(u) ((u) & 0x80000000U) /* mask all but highest bit of u */
+#define loBit(u) ((u) & 0x00000001U) /* mask all but lowest bit of u */
+#define loBits(u) ((u) & 0x7FFFFFFFU) /* mask the highest bit of u */
+#define mixBits(u, v) (hiBit(u)|loBits(v)) /* move hi bit of u to hi bit of v */
+
+static unsigned long state[N+1]; /* state vector + 1 extra to not violate ANSI C */
+static unsigned long *next; /* next random value is computed from here */
+static int left = -1; /* can *next++ this many times before reloading */
+
+
+void mt_seed(unsigned long seed)
+{
+ register unsigned long x = (seed | 1U) & 0xFFFFFFFFU, *s = state;
+ register int j;
+
+ for(left=0, *s++=x, j=N; --j;
+ *s++ = (x*=69069U) & 0xFFFFFFFFU);
+}
+
+
+unsigned long mt_reload(void)
+{
+ register unsigned long *p0=state, *p2=state+2, *pM=state+M, s0, s1;
+ register int j;
+
+ if(left < -1)
+ mt_seed(time(NULL));
+
+ left=N-1, next=state+1;
+
+ for(s0=state[0], s1=state[1], j=N-M+1; --j; s0=s1, s1=*p2++)
+ *p0++ = *pM++ ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
+
+ for(pM=state, j=M; --j; s0=s1, s1=*p2++)
+ *p0++ = *pM++ ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
+
+ s1=state[0], *p0 = *pM ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
+ s1 ^= (s1 >> 11);
+ s1 ^= (s1 << 7) & 0x9D2C5680U;
+ s1 ^= (s1 << 15) & 0xEFC60000U;
+ return(s1 ^ (s1 >> 18));
+}
+
+
+unsigned long mt_random(void)
+{
+ unsigned long y;
+
+ if(--left < 0)
+ return(mt_reload());
+
+ y = *next++;
+ y ^= (y >> 11);
+ y ^= (y << 7) & 0x9D2C5680U;
+ y ^= (y << 15) & 0xEFC60000U;
+ return(y ^ (y >> 18));
+}