Fix random moves when time < 10ms

[stockfish] / src / rkiss.h

diff --git a/src/rkiss.h b/src/rkiss.h
index 6e94dc27fa723fc8426216df2fbf0bf3cf2e452c..9564253b91a81301a70fd029163eac470248187c 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
-
-  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) 2008-2013 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.
@@ -25,53 +16,59 @@
   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
- ** *********************************************************************** **/
-
-#ifndef _RKISS_H_
-#define _RKISS_H_
+  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
 
-/** Includes **/
-#include <cstdlib>    // srand(), rand()
-#include <ctime>      // time()
-#include "types.h"    // (u)int8_t .. (u)int64_t
+class RKISS {
 
+  struct S { uint64_t a, b, c, d; } s; // Keep variables always together
 
-/** Random class **/
-class RKISS {
+  uint64_t rotate(uint64_t x, uint64_t k) const {
+    return (x << k) | (x >> (64 - k));
+  }
 
-private:
-       // Keep variables always together
-       struct S { uint64_t a; uint64_t b; uint64_t c; uint64_t d; } s;
+  uint64_t rand64() {
 
-       // Init seed and scramble a few rounds
-       void raninit ( uint64_t seed ) {
-               s.a = 0xf1ea5eed; s.b = s.c = s.d = seed;
-               for ( uint64_t i=0; i<8; i++ ) rand64();
-       }
+    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;
+  }
 
 public:
-       // Instance seed random or implicite
-       RKISS() { ::srand ( (uint32_t)time(NULL) ); raninit ( (uint64_t)::rand() ); }
-       // RKISS( uint64_t s ) { raninit ( s ); }
-
-       // (Re)init seed
-       // void init ( uint64_t seed ) { raninit ( seed ); }
-
-       // Return 32 bit unsigned integer in between [0,2^32-1]
-       uint32_t rand32 () { return (uint32_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;
-       }
-
-       // Return double in between [0,1). Keep full 53 bit mantissa
-       // double frand () { return (int64_t)(rand64()>>11) * (1.0/(67108864.0*134217728.0)); }
+  RKISS(int seed = 73) {
+
+    s.a = 0xf1ea5eed;
+    s.b = s.c = s.d = 0xd4e12c77;
+    for (int i = 0; i < seed; i++) // Scramble a few rounds
+        rand64();
+  }
+
+  template<typename T> T rand() { return T(rand64()); }
 };
 
-// _RKISS_H_
-#endif
+#endif // #ifndef RKISS_H_INCLUDED