/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
available under the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
-
- ** A small "keep it simple and stupid" RNG with some fancy merits:
- **
- ** Quite platform independent
- ** Passes ALL dieharder tests! Here *nix sys-rand() e.g. fails miserably:-)
- ** ~12 times faster than my *nix sys-rand()
- ** ~4 times faster than SSE2-version of Mersenne twister
- ** Average cycle length: ~2^126
- ** 64 bit seed
- ** Return doubles with a full 53 bit mantissa
- ** Thread safe
- **
- ** (c) Heinz van Saanen
-
*/
#if !defined(RKISS_H_INCLUDED)
#include "types.h"
+/// RKISS is our pseudo random number generator (PRNG) used to compute hash keys.
+/// George Marsaglia invented the RNG-Kiss-family in the early 90's. This is a
+/// specific version that Heinz van Saanen derived from some public domain code
+/// by Bob Jenkins. Following the feature list, as tested by Heinz.
+///
+/// - Quite platform independent
+/// - Passes ALL dieharder tests! Here *nix sys-rand() e.g. fails miserably:-)
+/// - ~12 times faster than my *nix sys-rand()
+/// - ~4 times faster than SSE2-version of Mersenne twister
+/// - Average cycle length: ~2^126
+/// - 64 bit seed
+/// - Return doubles with a full 53 bit mantissa
+/// - Thread safe
+
class RKISS {
// Keep variables always together
struct S { uint64_t a, b, c, d; } s;
- // Return 64 bit unsigned integer in between [0,2^64-1]
+ uint64_t rotate(uint64_t x, uint64_t k) const {
+ return (x << k) | (x >> (64 - k));
+ }
+
+ // Return 64 bit unsigned integer in between [0, 2^64 - 1]
uint64_t rand64() {
- const uint64_t
- e = s.a - ((s.b << 7) | (s.b >> 57));
- s.a = s.b ^ ((s.c << 13) | (s.c >> 51));
- s.b = s.c + ((s.d << 37) | (s.d >> 27));
- s.c = s.d + e;
- return s.d = e + s.a;
+ const uint64_t
+ e = s.a - rotate(s.b, 7);
+ s.a = s.b ^ rotate(s.c, 13);
+ s.b = s.c + rotate(s.d, 37);
+ s.c = s.d + e;
+ return s.d = e + s.a;
}
- // Init seed and scramble a few rounds
- void raninit() {
+public:
+ RKISS(int seed = 73) {
- s.a = 0xf1ea5eed;
- s.b = s.c = s.d = 0xd4e12c77;
- for (int i = 0; i < 73; i++)
- rand64();
+ s.a = 0xf1ea5eed;
+ s.b = s.c = s.d = 0xd4e12c77;
+ for (int i = 0; i < seed; i++) // Scramble a few rounds
+ rand64();
}
-public:
- RKISS() { raninit(); }
template<typename T> T rand() { return T(rand64()); }
};