X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Frkiss.h;h=154f3ca2d9252c5f1952498a8fd95b588c67e9d0;hp=13f0640765a1ba42f23413ecc65b4cfe3bf22dc8;hb=55bd27b8f08a151128d7065fa2819aa3e9605299;hpb=8fb16df70e032c782b6bf81b211e8dab1724a7dc

diff --git a/src/rkiss.h b/src/rkiss.h
index 13f06407..154f3ca2 100644
--- a/src/rkiss.h
+++ b/src/rkiss.h
@@ -1,23 +1,14 @@
-/** *********************************************************************** **
- ** 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 save
- **
- ** (c) Heinz van Saanen
-
-  This file is free software: you can redistribute it and/or modify
+/*
+  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
+  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
+  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
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
 
-  This file is distributed in the hope that it will be useful,
+  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.
@@ -25,58 +16,63 @@
   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.
+*/
 
 #if !defined(RKISS_H_INCLUDED)
 #define RKISS_H_INCLUDED
 
-
-////
-//// Includes
-////
-
-#include <cstdlib>
-#include <ctime>
-
 #include "types.h"
 
-
-////
-//// Types
-////
+/// 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;
+  // 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 rand64() {
+  uint64_t rotate(uint64_t x, uint64_t k) const {
+    return (x << k) | (x >> (64 - k));
+  }
 
-		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;
-	}
+  // Return 64 bit unsigned integer in between [0, 2^64 - 1]
+  uint64_t rand64() {
 
-	// Init seed and scramble a few rounds
-	void raninit(uint64_t seed) {
+    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;
+  }
 
-		s.a = 0xf1ea5eed;
-        s.b = s.c = s.d = seed;
-		for (uint64_t i = 0; i < 8; i++)
-            rand64();
-	}
+  // Init seed and scramble a few rounds
+  void raninit() {
 
-public:
-	// Instance seed random or implicite
-	RKISS() { ::srand(uint32_t(time(NULL))); raninit(uint64_t(::rand())); }
+    s.a = 0xf1ea5eed;
+    s.b = s.c = s.d = 0xd4e12c77;
+    for (int i = 0; i < 73; i++)
+        rand64();
+  }
 
-	// Return random number of type T (must be castable from uint64_t)
-    template<typename T>
-	T rand() { return T(rand64()); }
+public:
+  RKISS() { raninit(); }
+  template<typename T> T rand() { return T(rand64()); }
 };
 
 #endif // !defined(RKISS_H_INCLUDED)