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79 lines
2.5 KiB
C++
79 lines
2.5 KiB
C++
/*
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Stockfish, a UCI chess playing engine derived from Glaurung 2.1
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Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
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Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
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Stockfish is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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Stockfish is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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This file is based on original code by Heinz van Saanen and is
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available under the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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*/
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#if !defined(RKISS_H_INCLUDED)
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#define RKISS_H_INCLUDED
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#include "types.h"
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/// RKISS is our pseudo random number generator (PRNG) used to compute hash keys.
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/// George Marsaglia invented the RNG-Kiss-family in the early 90's. This is a
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/// specific version that Heinz van Saanen derived from some public domain code
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/// by Bob Jenkins. Following the feature list, as tested by Heinz.
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///
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/// - Quite platform independent
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/// - Passes ALL dieharder tests! Here *nix sys-rand() e.g. fails miserably:-)
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/// - ~12 times faster than my *nix sys-rand()
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/// - ~4 times faster than SSE2-version of Mersenne twister
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/// - Average cycle length: ~2^126
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/// - 64 bit seed
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/// - Return doubles with a full 53 bit mantissa
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/// - Thread safe
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class RKISS {
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// Keep variables always together
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struct S { uint64_t a, b, c, d; } s;
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uint64_t rotate(uint64_t x, uint64_t k) const {
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return (x << k) | (x >> (64 - k));
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}
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// Return 64 bit unsigned integer in between [0, 2^64 - 1]
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uint64_t rand64() {
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const uint64_t
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e = s.a - rotate(s.b, 7);
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s.a = s.b ^ rotate(s.c, 13);
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s.b = s.c + rotate(s.d, 37);
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s.c = s.d + e;
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return s.d = e + s.a;
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}
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// Init seed and scramble a few rounds
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void raninit() {
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s.a = 0xf1ea5eed;
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s.b = s.c = s.d = 0xd4e12c77;
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for (int i = 0; i < 73; i++)
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rand64();
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}
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public:
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RKISS() { raninit(); }
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template<typename T> T rand() { return T(rand64()); }
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};
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#endif // !defined(RKISS_H_INCLUDED)
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