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xorshift32 PRNG for Math::rand_from_seed()

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should fixes #1043

PRNG adapted from : http://excamera.com/sphinx/article-xorshift.html
This commit is contained in:
yg2f
2016-10-09 02:21:44 +02:00
parent 1f9e16119f
commit a747c8ccee
1 changed files with 8 additions and 29 deletions
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37
core/math/math_funcs.cpp
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@@ -41,37 +41,16 @@ static uint32_t Q[4096];
#endif #endif
uint32_t Math::rand_from_seed(uint32_t *seed) { uint32_t Math::rand_from_seed(uint32_t *seed) {
// Xorshift31 PRNG
#if 1 if ( *seed == 0 ) *seed = Math::RANDOM_MAX;
uint32_t k; (*seed) ^= (*seed) << 13;
uint32_t s = (*seed); (*seed) ^= (*seed) >> 17;
if (s == 0) (*seed) ^= (*seed) << 5;
s = 0x12345987; return (*seed) & Math::RANDOM_MAX;
k = s / 127773;
s = 16807 * (s - k * 127773) - 2836 * k;
// if (s < 0)
// s += 2147483647;
(*seed) = s;
return (s & Math::RANDOM_MAX);
#else
*seed = *seed * 1103515245 + 12345;
return (*seed % ((unsigned int)RANDOM_MAX + 1));
#endif
} }
void Math::seed(uint32_t x) { void Math::seed(uint32_t x) {
#if 0
int i;
Q[0] = x;
Q[1] = x + PHI;
Q[2] = x + PHI + PHI;
for (i = 3; i < 4096; i++)
Q[i] = Q[i - 3] ^ Q[i - 2] ^ PHI ^ i;
#else
default_seed=x; default_seed=x;
#endif
} }
void Math::randomize() { void Math::randomize() {
@@ -82,12 +61,12 @@ void Math::randomize() {
uint32_t Math::rand() { uint32_t Math::rand() {
return rand_from_seed(&default_seed)&0x7FFFFFFF; return rand_from_seed(&default_seed);
} }
double Math::randf() { double Math::randf() {
return (double)rand() / (double)RANDOM_MAX; return (double)rand() / (double)Math::RANDOM_MAX;
} }
double Math::sin(double p_x) { double Math::sin(double p_x) {