mirror of
https://github.com/TerryCavanagh/VVVVVV.git
synced 2026-01-30 01:48:15 +03:00
424c8c80be
This is useful to investigate any TAS desync/reproducibility issues relating to RNG, because even though I specifically separated the Gravitron RNG away from other RNG and made it not dependent on the system libc rand() function, there's still apparently some differences in RNG execution between systems, resulting in TASVideos submission 7575 ( https://tasvideos.org/7575S ) not syncing for everyone except the author. It seems that SDL_GetTicks(), which is used to seed the xoshiro RNG, is not reliably consistent between systems, so in the future I will probably replace it with a counter that is incremented each frame starting from game startup, which is probably better.
69 lines
1.2 KiB
C
69 lines
1.2 KiB
C
#include <stdint.h>
|
|
|
|
#include "Vlogging.h"
|
|
|
|
/* Implements the xoshiro128+ PRNG. */
|
|
|
|
static uint32_t rotl(const uint32_t x, const int k)
|
|
{
|
|
return (x << k) | (x >> (32 - k));
|
|
}
|
|
|
|
static uint32_t s[4];
|
|
|
|
static uint32_t splitmix32(uint32_t* x)
|
|
{
|
|
uint32_t z = (*x += 0x9e3779b9UL);
|
|
z = (z ^ (z >> 15)) * 0xbf58476dUL;
|
|
z = (z ^ (z >> 13)) * 0x94d049bbUL;
|
|
return z ^ (z >> 16);
|
|
}
|
|
|
|
static void seed(
|
|
const uint32_t s0,
|
|
const uint32_t s1,
|
|
const uint32_t s2,
|
|
const uint32_t s3
|
|
) {
|
|
s[0] = s0;
|
|
s[1] = s1;
|
|
s[2] = s2;
|
|
s[3] = s3;
|
|
}
|
|
|
|
uint32_t xoshiro_next(void)
|
|
{
|
|
const uint32_t result = s[0] + s[3];
|
|
|
|
const uint32_t t = s[1] << 9;
|
|
|
|
s[2] ^= s[0];
|
|
s[3] ^= s[1];
|
|
s[1] ^= s[2];
|
|
s[0] ^= s[3];
|
|
|
|
s[2] ^= t;
|
|
|
|
s[3] = rotl(s[3], 11);
|
|
|
|
vlog_debug("Next xoshiro is %u.", result);
|
|
|
|
return result;
|
|
}
|
|
|
|
void xoshiro_seed(uint32_t s)
|
|
{
|
|
const uint32_t s0 = splitmix32(&s);
|
|
const uint32_t s1 = splitmix32(&s);
|
|
const uint32_t s2 = splitmix32(&s);
|
|
const uint32_t s3 = splitmix32(&s);
|
|
seed(s0, s1, s2, s3);
|
|
|
|
vlog_debug("Xoshiro seeded with %u.", s);
|
|
}
|
|
|
|
float xoshiro_rand(void)
|
|
{
|
|
return ((float) xoshiro_next()) / ((float) UINT32_MAX);
|
|
}
|