From 3fd43cd5fcb22bb65bf2a92a25d95d801b11c9e0 Mon Sep 17 00:00:00 2001 From: Scott Gasch Date: Wed, 1 Jun 2016 18:58:58 -0700 Subject: Initial checkin for typhoon chess engine. --- src/mersenne.c | 168 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 168 insertions(+) create mode 100644 src/mersenne.c (limited to 'src/mersenne.c') diff --git a/src/mersenne.c b/src/mersenne.c new file mode 100644 index 0000000..68eef94 --- /dev/null +++ b/src/mersenne.c @@ -0,0 +1,168 @@ +// +// 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 +// (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 with +// an appropriate reference to your work. +// +// It would be nice to CC: when you write. +// + +// +// Note: This code is used with permission +// +// $Id: mersenne.c 7 2004-07-01 15:46:42Z scott $ +// + +#include +#include + +// +// uint32 must be an unsigned integer type capable of holding at least 32 +// bits; exactly 32 should be fastest, but 64 is better on an Alpha with +// GCC at -O3 optimization so try your options and see what's best for you +// + +#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 int state[N+1]; // state vector + 1 extra to not violate ANSI C +static unsigned int *next; // next random value is computed from here +static int left = -1; // can *next++ this many times before reloading + + +void seedMT(unsigned int seed) +{ + // + // We initialize state[0..(N-1)] via the generator + // + // x_new = (69069 * x_old) mod 2^32 + // + // from Line 15 of Table 1, p. 106, Sec. 3.3.4 of Knuth's + // _The Art of Computer Programming_, Volume 2, 3rd ed. + // + // Notes (SJC): I do not know what the initial state requirements + // of the Mersenne Twister are, but it seems this seeding generator + // could be better. It achieves the maximum period for its modulus + // (2^30) iff x_initial is odd (p. 20-21, Sec. 3.2.1.2, Knuth); if + // x_initial can be even, you have sequences like 0, 0, 0, ...; + // 2^31, 2^31, 2^31, ...; 2^30, 2^30, 2^30, ...; 2^29, 2^29 + 2^31, + // 2^29, 2^29 + 2^31, ..., etc. so I force seed to be odd below. + // + // Even if x_initial is odd, if x_initial is 1 mod 4 then + // + // the lowest bit of x is always 1, + // the next-to-lowest bit of x is always 0, + // the 2nd-from-lowest bit of x alternates ... 0 1 0 1 0 1 0 1 ... , + // the 3rd-from-lowest bit of x 4-cycles ... 0 1 1 0 0 1 1 0 ... , + // the 4th-from-lowest bit of x has the 8-cycle ... 0 0 0 1 1 1 1 0 ... , + // ... + // + // and if x_initial is 3 mod 4 then + // + // the lowest bit of x is always 1, + // the next-to-lowest bit of x is always 1, + // the 2nd-from-lowest bit of x alternates ... 0 1 0 1 0 1 0 1 ... , + // the 3rd-from-lowest bit of x 4-cycles ... 0 0 1 1 0 0 1 1 ... , + // the 4th-from-lowest bit of x has the 8-cycle ... 0 0 1 1 1 1 0 0 ... , + // ... + // + // The generator's potency (min. s>=0 with (69069-1)^s = 0 mod 2^32) is + // 16, which seems to be alright by p. 25, Sec. 3.2.1.3 of Knuth. It + // also does well in the dimension 2..5 spectral tests, but it could be + // better in dimension 6 (Line 15, Table 1, p. 106, Sec. 3.3.4, Knuth). + // + // Note that the random number user does not see the values generated + // here directly since reloadMT() will always munge them first, so maybe + // none of all of this matters. In fact, the seed values made here could + // even be extra-special desirable if the Mersenne Twister theory says + // so-- that's why the only change I made is to restrict to odd seeds. + // + + register unsigned int x = (seed | 1U) & 0xFFFFFFFFU, *s = state; + register int j; + + for(left=0, *s++=x, j=N; --j; + *s++ = (x*=69069U) & 0xFFFFFFFFU); +} + + +unsigned int +reloadMT(void) +{ + register unsigned int *p0=state, *p2=state+2, *pM=state+M, s0, s1; + register int j; + + if(left < -1) + seedMT(4357U); + + 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 int randomMT(void) +{ + unsigned int y; + + if(--left < 0) + return(reloadMT()); + + y = *next++; + y ^= (y >> 11); + y ^= (y << 7) & 0x9D2C5680U; + y ^= (y << 15) & 0xEFC60000U; + return(y ^ (y >> 18)); +} -- cgit v1.3