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random: Use sfc64 instead of gjrand.

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Nicholas J. Kain 2022-10-13 08:43:11 -04:00
parent 1c1ea86604
commit 1b8dc7f05e
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1 changed files with 11 additions and 18 deletions
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nk/random.c
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@ -1,17 +1,16 @@
// Copyright 2013-2018 Nicholas J. Kain <njkain at gmail dot com> // Copyright 2013-2022 Nicholas J. Kain <njkain at gmail dot com>
// SPDX-License-Identifier: MIT // SPDX-License-Identifier: MIT
#include <stdint.h> #include <stdint.h>
#include "nk/hwrng.h" #include "nk/hwrng.h"
#include "nk/random.h" #include "nk/random.h"
// GJrand64: https://gjrand.sourceforge.net // SFC64 modified to use a Weyl counter.
void nk_random_init(struct nk_random_state *s) void nk_random_init(struct nk_random_state *s)
{ {
nk_hwrng_bytes(s->seed, sizeof(uint64_t) * 2); nk_hwrng_bytes(s->seed, sizeof(uint64_t) * 3);
s->seed[2] = 2000001; s->seed[3] = 1;
s->seed[3] = 0; for (size_t i = 0; i < 12; ++i) nk_random_u64(s);
for (size_t i = 0; i < 14; ++i) nk_random_u64(s);
} }
static inline uint64_t rotl64(const uint64_t x, int k) { static inline uint64_t rotl64(const uint64_t x, int k) {
@ -20,17 +19,11 @@ static inline uint64_t rotl64(const uint64_t x, int k) {
uint64_t nk_random_u64(struct nk_random_state *s) uint64_t nk_random_u64(struct nk_random_state *s)
{ {
s->seed[1] += s->seed[2]; const uint64_t t = (s->seed[0] + s->seed[1]) ^ s->seed[3];
s->seed[0] = rotl64(s->seed[0], 32); s->seed[3] += 0x6a09e667a7541669ull;
s->seed[2] ^= s->seed[1]; s->seed[0] = s->seed[1] ^ (s->seed[1] >> 11);
s->seed[3] += 0x55aa96a5; s->seed[1] = s->seed[2] + (s->seed[2] << 3);
s->seed[0] += s->seed[1]; s->seed[2] = rotl64(s->seed[2], 24) + t;
s->seed[2] = rotl64(s->seed[2], 23); return t;
s->seed[1] ^= s->seed[0];
s->seed[0] += s->seed[2];
s->seed[1] = rotl64(s->seed[1], 19);
s->seed[2] += s->seed[0];
s->seed[1] += s->seed[3];
return s->seed[0];
} }