Simpler PRNG and faster magics search

[stockfish] / src / rkiss.h

diff --git a/src/rkiss.h b/src/rkiss.h
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-/*
-  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