From 4c9004671af455a03acb4e2750b12d62b2b3c917 Mon Sep 17 00:00:00 2001 From: Ferenc Arn Date: Sat, 14 Jan 2017 23:34:51 -0600 Subject: Replace the existing PRNG (Xorshift31) with (minimal) PCG (XSH-RR variant with 32-bit output, 64-bit state). PCG is better than many alternatives by many metrics (see www.pcg-random.org) including statistical quality with good speed. --- core/math/math_funcs.cpp | 25 ++++++++++++------------- 1 file changed, 12 insertions(+), 13 deletions(-) (limited to 'core/math/math_funcs.cpp') diff --git a/core/math/math_funcs.cpp b/core/math/math_funcs.cpp index 8353aa0ebe..ef8c1ec539 100644 --- a/core/math/math_funcs.cpp +++ b/core/math/math_funcs.cpp @@ -31,8 +31,9 @@ #include "core/os/os.h" #include "float.h" -uint32_t Math::default_seed=1; +#include "pcg.h" +pcg32_random_t Math::default_pcg = {1, PCG_DEFAULT_INC_64}; #define PHI 0x9e3779b9 @@ -40,28 +41,26 @@ uint32_t Math::default_seed=1; static uint32_t Q[4096]; #endif -uint32_t Math::rand_from_seed(uint32_t *seed) { - // Xorshift31 PRNG - if ( *seed == 0 ) *seed = Math::RANDOM_MAX; - (*seed) ^= (*seed) << 13; - (*seed) ^= (*seed) >> 17; - (*seed) ^= (*seed) << 5; - return (*seed) & Math::RANDOM_MAX; +// TODO: we should eventually expose pcg.inc too +uint32_t Math::rand_from_seed(uint64_t *seed) { + pcg32_random_t pcg = {*seed, PCG_DEFAULT_INC_64}; + uint32_t r = pcg32_random_r(&pcg); + *seed = pcg.state; + return r; } -void Math::seed(uint32_t x) { - default_seed=x; +void Math::seed(uint64_t x) { + default_pcg.state=x; } void Math::randomize() { OS::Time time = OS::get_singleton()->get_time(); - seed(OS::get_singleton()->get_ticks_usec()*(time.hour+1)*(time.min+1)*(time.sec+1)*rand()); /* *OS::get_singleton()->get_time().sec); // windows doesn't have get_time(), returns always 0 */ + seed(OS::get_singleton()->get_ticks_usec()*(time.hour+1)*(time.min+1)*(time.sec+1)*rand()); // TODO: can be simplified. } uint32_t Math::rand() { - - return rand_from_seed(&default_seed); + return pcg32_random_r(&default_pcg); } double Math::randf() { -- cgit v1.2.3