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)
#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));
}
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;
}