Make rkiss seed deterministic

Search at fixed depth with one thread must be
reproducible so remove randomess from time().

Also better license description.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

diff --git a/src/rkiss.h b/src/rkiss.h
index 13f0640765a1ba42f23413ecc65b4cfe3bf22dc8..22ab50378f8f87a4c972749db588ae7cbd7b523a 100644 (file)
--- 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
+/*
+  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
+  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
+  Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
 
-  This file is free software: you can redistribute it and/or modify
+  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.
@@ -25,7 +16,25 @@
   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.
+
+ ** 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 safe
+ **
+ ** (c) Heinz van Saanen
+
+*/
 
 #if !defined(RKISS_H_INCLUDED)
 #define RKISS_H_INCLUDED
@@ -35,9 +44,6 @@
 //// Includes
 ////
 
-#include <cstdlib>
-#include <ctime>
-
 #include "types.h"
 
 
@@ -47,36 +53,32 @@
 
 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() {
+  // Return 64 bit unsigned integer in between [0,2^64-1]
+  uint64_t rand64() {
 
-               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;
-       }
+      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;
+  }
 
-       // Init seed and scramble a few rounds
-       void raninit(uint64_t seed) {
+  // Init seed and scramble a few rounds
+  void raninit() {
 
-               s.a = 0xf1ea5eed;
-        s.b = s.c = s.d = seed;
-               for (uint64_t i = 0; i < 8; i++)
-            rand64();
-       }
+      s.a = 0xf1ea5eed;
+      s.b = s.c = s.d = 0xd4e12c77;
+      for (uint64_t i = 0; i < 73; i++)
+          rand64();
+  }
 
 public:
-       // Instance seed random or implicite
-       RKISS() { ::srand(uint32_t(time(NULL))); raninit(uint64_t(::rand())); }
-
-       // Return random number of type T (must be castable from uint64_t)
-    template<typename T>
-       T rand() { return T(rand64()); }
+  RKISS() { raninit(); }
+  template<typename T> T rand() { return T(rand64()); }
 };
 
 #endif // !defined(RKISS_H_INCLUDED)