mirror of
https://github.com/peterosterlund2/droidfish.git
synced 2024-12-04 17:30:56 +01:00
82 lines
2.7 KiB
C++
82 lines
2.7 KiB
C++
/*
|
|
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 <http://www.gnu.org/licenses/>.
|
|
|
|
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<typename T> 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<typename T> T magic_rand(int s) {
|
|
return rotate_L(rotate_L(rand<T>(), (s >> 0) & 0x3F) & rand<T>()
|
|
, (s >> 6) & 0x3F) & rand<T>();
|
|
}
|
|
};
|
|
|
|
#endif // #ifndef RKISS_H_INCLUDED
|