Use Heinz's RKiss instead of marsenne

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

src/rkiss.h

@@ -0,0 +1,77 @@
+/** *********************************************************************** **
+ ** 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
+  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,
+  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/>.
+
+ ** *********************************************************************** **/
+
+#ifndef _RKISS_H_
+#define _RKISS_H_
+
+/** Includes **/
+#include <cstdlib>    // srand(), rand()
+#include <ctime>      // time()
+#include "types.h"    // (u)int8_t .. (u)int64_t
+
+
+/** Random class **/
+class RKISS {
+
+private:
+	// Keep variables always together
+	struct S { uint64_t a; uint64_t b; uint64_t c; uint64_t d; } s;
+
+	// 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();
+	}
+
+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_H_
+#endif