Changeset: 151aead76f5b for MonetDB URL: https://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=151aead76f5b Modified Files: gdk/xoshiro256starstar.h Branch: default Log Message:
Use splitmix64 generator to transform the seed into a PRNG state. The splitmix64 generator is from the same source as xoshiro256**. Also added some comments and removed (now) unused stuff. diffs (80 lines): diff --git a/gdk/xoshiro256starstar.h b/gdk/xoshiro256starstar.h --- a/gdk/xoshiro256starstar.h +++ b/gdk/xoshiro256starstar.h @@ -1,32 +1,49 @@ -#include <stdint.h> -#include <string.h> -#include "gdk.h" - /* -This 64 bit pseudo random number generator is based on the engine written by -Sebastiano Vigna from Dipartimento di Informatica of the Università degli Studi di Milano. -The original source code can be found here http://xoshiro.di.unimi.it/xoshiro256starstar.c. -The engine is supposed to perform very well on various random engine benchmarks. -The original author offered his work to the public domain. +This 64 bit pseudo random number generator is based on the engine +written by Sebastiano Vigna from Dipartimento di Informatica of the +Università degli Studi di Milano. The original source code can be +found here http://xoshiro.di.unimi.it/xoshiro256starstar.c. The +engine is supposed to perform very well on various random engine +benchmarks. +The original author offered his work to the public domain per the +following original comment. */ -static inline ulng rotl(const ulng x, int k) { +/* Written in 2018 by David Blackman and Sebastiano Vigna (vi...@acm.org) + +To the extent possible under law, the author has dedicated all copyright +and related and neighboring rights to this software to the public domain +worldwide. This software is distributed without any warranty. + +See <http://creativecommons.org/publicdomain/zero/1.0/>. */ + +static inline uint64_t rotl(const uint64_t x, int k) { return (x << k) | (x >> (64 - k)); } -typedef ulng random_state_engine[4]; - -static inline void init_random_state_engine(random_state_engine* engine, const unsigned seed) { +typedef uint64_t random_state_engine[4]; - random_state_engine s = { seed << 1, seed + 1, seed >> 1, seed - 1 }; - - memcpy(engine, &s, sizeof(random_state_engine)); +static inline void +init_random_state_engine(random_state_engine engine, uint64_t seed) +{ + for (int i = 0; i < 4; i++) { + /* we use the splitmix64 generator to generate the 4 + * values in the state array from the given seed. + * This code is adapted from + * http://xoshiro.di.unimi.it/splitmix64.c which was + * put in the public domain in the same way as the + * "next" function below. */ + uint64_t z = (seed += 0x9e3779b97f4a7c15); + z = (z ^ (z >> 30)) * 0xbf58476d1ce4e5b9; + z = (z ^ (z >> 27)) * 0x94d049bb133111eb; + engine[i] = z ^ (z >> 31); + } } -static inline ulng next(random_state_engine rse) { - const ulng output = rotl(rse[0] * 5, 7) * 9; +static inline uint64_t next(random_state_engine rse) { + const uint64_t output = rotl(rse[0] * 5, 7) * 9; - const ulng t = rse[1] << 17; + const uint64_t t = rse[1] << 17; rse[2] ^= rse[0]; rse[3] ^= rse[1]; @@ -39,7 +56,3 @@ static inline ulng next(random_state_eng return output; } - -static inline double next_double(random_state_engine rse) { - return (double) next(rse) / UINT64_MAX; -} _______________________________________________ checkin-list mailing list checkin-list@monetdb.org https://www.monetdb.org/mailman/listinfo/checkin-list
