diff options
| author | yg2f <yoann@terminajones.com> | 2016-10-09 02:21:44 +0200 |
|---|---|---|
| committer | yg2f <yoann@terminajones.com> | 2016-10-10 20:41:36 +0200 |
| commit | a747c8cceea53cd6dd02f4c41f062549afbbcac1 (patch) | |
| tree | ac1cd178be37a0571b46bb50d6d97cfd8826e48a | |
| parent | 1f9e16119f2b17fa507bdee8529459ed91f27b8c (diff) | |
xorshift32 PRNG for Math::rand_from_seed()
should fixes #1043
PRNG adapted from : http://excamera.com/sphinx/article-xorshift.html
| -rw-r--r-- | core/math/math_funcs.cpp | 37 |
1 files changed, 8 insertions, 29 deletions
diff --git a/core/math/math_funcs.cpp b/core/math/math_funcs.cpp index 64615fe6b4..46c0218707 100644 --- a/core/math/math_funcs.cpp +++ b/core/math/math_funcs.cpp @@ -41,37 +41,16 @@ static uint32_t Q[4096]; #endif uint32_t Math::rand_from_seed(uint32_t *seed) { - -#if 1 - uint32_t k; - uint32_t s = (*seed); - if (s == 0) - s = 0x12345987; - 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 + // Xorshift31 PRNG + if ( *seed == 0 ) *seed = Math::RANDOM_MAX; + (*seed) ^= (*seed) << 13; + (*seed) ^= (*seed) >> 17; + (*seed) ^= (*seed) << 5; + return (*seed) & Math::RANDOM_MAX; } 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; -#endif } void Math::randomize() { @@ -82,12 +61,12 @@ void Math::randomize() { uint32_t Math::rand() { - return rand_from_seed(&default_seed)&0x7FFFFFFF; + return rand_from_seed(&default_seed); } double Math::randf() { - return (double)rand() / (double)RANDOM_MAX; + return (double)rand() / (double)Math::RANDOM_MAX; } double Math::sin(double p_x) { |