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Add split_mix_64 utility

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Abdelrahman Said 2024-03-22 12:37:46 +00:00
parent 05b9a22174
commit e4893c150b
1 changed files with 21 additions and 4 deletions
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25
xorshift.c
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@ -4,6 +4,10 @@
#include <stdlib.h> #include <stdlib.h>
#include <time.h> #include <time.h>
typedef struct {
u64 seed;
} SplitMix64State;
typedef struct { typedef struct {
u64 x; u64 x;
u64 y; u64 y;
@ -22,6 +26,7 @@ u64 xoshiro_256p_generate(void *s);
u64 rol64(u64 x, u64 bits); u64 rol64(u64 x, u64 bits);
XOR256State init_xor_256_state(); XOR256State init_xor_256_state();
void write_image_data(Image *img, RandGenFunc *gen_rand, void *s); void write_image_data(Image *img, RandGenFunc *gen_rand, void *s);
u64 split_mix_64(SplitMix64State *state);
int main(int argc, char *argv[]) { int main(int argc, char *argv[]) {
struct timespec ts = {0}; struct timespec ts = {0};
@ -115,11 +120,13 @@ u64 xoshiro_256p_generate(void *s) {
u64 rol64(u64 x, u64 bits) { return (x << bits) | (x >> (64 - bits)); } u64 rol64(u64 x, u64 bits) { return (x << bits) | (x >> (64 - bits)); }
XOR256State init_xor_256_state() { XOR256State init_xor_256_state() {
SplitMix64State sm64 = {.seed = lrand48()};
return (XOR256State){ return (XOR256State){
.x = lrand48(), .x = split_mix_64(&sm64),
.y = lrand48(), .y = split_mix_64(&sm64),
.z = lrand48(), .z = split_mix_64(&sm64),
.w = lrand48(), .w = split_mix_64(&sm64),
}; };
} }
@ -137,3 +144,13 @@ void write_image_data(Image *img, RandGenFunc *gen_rand, void *s) {
} }
} }
} }
u64 split_mix_64(SplitMix64State *state) {
state->seed += 0x9E3779B97f4A7C15;
u64 result = state->seed;
result = (result ^ (result >> 30)) * 0xBF58476D1CE4E5B9;
result = (result ^ (result >> 27)) * 0x94D049BB133111EB;
return result ^ (result >> 31);
}