X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Frkiss.h;h=154f3ca2d9252c5f1952498a8fd95b588c67e9d0;hp=0863c9cf7520ce279c4f1666f97e17d4ae52f290;hb=55bd27b8f08a151128d7065fa2819aa3e9605299;hpb=76506bd3d10214aa3f3d12dad60e8da729fc318c

diff --git a/src/rkiss.h b/src/rkiss.h
index 0863c9cf..154f3ca2 100644
--- a/src/rkiss.h
+++ b/src/rkiss.h
@@ -1,7 +1,7 @@
 /*
   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
+  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
@@ -20,20 +20,6 @@
   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)
@@ -41,12 +27,26 @@
 
 #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 {
 
   // Keep variables always together
   struct S { uint64_t a, b, c, d; } s;
 
-  uint64_t rot(uint64_t x, uint64_t k) const {
+  uint64_t rotate(uint64_t x, uint64_t k) const {
     return (x << k) | (x >> (64 - k));
   }
 
@@ -54,9 +54,9 @@ class RKISS {
   uint64_t rand64() {
 
     const uint64_t
-      e = s.a - rot(s.b,  7);
-    s.a = s.b ^ rot(s.c, 13);
-    s.b = s.c + rot(s.d, 37);
+      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;
   }