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/* Written in 2019 by David Blackman and Sebastiano Vigna (vigna@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/>. */
#include <stdint.h>
#include <string.h>
/* This is xoshiro256++ 1.0, one of our all-purpose, rock-solid generators.
It has excellent (sub-ns) speed, a state (256 bits) that is large
enough for any parallel application, and it passes all tests we are
aware of.
For generating just floating-point numbers, xoshiro256+ is even faster.
The state must be seeded so that it is not everywhere zero. If you have
a 64-bit seed, we suggest to seed a splitmix64 generator and use its
output to fill s. */
static inline uint64_t rotl(const uint64_t x, int k) {
return (x << k) | (x >> (64 - k));
}
static uint64_t s[4];
void seed_xoshiro_256_pp(uint64_t input[4]) {
memcpy(s, input, sizeof(s));
}
uint64_t xoshiro_256_pp(void) {
const uint64_t result = rotl(s[0] + s[3], 23) + s[0];
const uint64_t t = s[1] << 17;
s[2] ^= s[0];
s[3] ^= s[1];
s[1] ^= s[2];
s[0] ^= s[3];
s[2] ^= t;
s[3] = rotl(s[3], 45);
return result;
}
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