/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2014 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
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see .
This file is based on original code by Heinz van Saanen and is
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.
*/
#ifndef RKISS_H_INCLUDED
#define 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 {
uint64_t a, b, c, d;
uint64_t rotate_L(uint64_t x, unsigned k) const {
return (x << k) | (x >> (64 - k));
}
uint64_t rand64() {
const uint64_t e = a - rotate_L(b, 7);
a = b ^ rotate_L(c, 13);
b = c + rotate_L(d, 37);
c = d + e;
return d = e + a;
}
public:
RKISS(int seed = 73) {
a = 0xF1EA5EED, b = c = d = 0xD4E12C77;
for (int i = 0; i < seed; ++i) // Scramble a few rounds
rand64();
}
template T rand() { return T(rand64()); }
/// Special generator used to fast init magic numbers. Here the
/// trick is to rotate the randoms of a given quantity 's' known
/// to be optimal to quickly find a good magic candidate.
template T magic_rand(int s) {
return rotate_L(rotate_L(rand(), (s >> 0) & 0x3F) & rand()
, (s >> 6) & 0x3F) & rand();
}
};
#endif // #ifndef RKISS_H_INCLUDED