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Properly setup seed in RNG 

(cherry picked from commit 6280be46a6)
This commit is contained in:
Chaosus 2019-03-17 20:51:51 +03:00 committed by Rémi Verschelde
parent 29a6e7d306
commit 1dd72dca45
4 changed files with 15 additions and 5 deletions
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3
core/math/random_pcg.cpp
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@ -34,8 +34,7 @@
RandomPCG::RandomPCG(uint64_t p_seed, uint64_t p_inc) :
pcg(),
current_seed(DEFAULT_SEED) {
pcg.inc = p_inc;
current_inc(p_inc) {
seed(p_seed);
}

6
core/math/random_pcg.h
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@ -38,18 +38,18 @@
class RandomPCG {
pcg32_random_t pcg;
uint64_t current_seed; // seed with this to get the same state
uint64_t current_inc;
public:
static const uint64_t DEFAULT_SEED = 12047754176567800795U;
static const uint64_t DEFAULT_INC = PCG_DEFAULT_INC_64;
static const uint64_t RANDOM_MAX = 0xFFFFFFFF;
RandomPCG(uint64_t p_seed = DEFAULT_SEED, uint64_t p_inc = PCG_DEFAULT_INC_64);
RandomPCG(uint64_t p_seed = DEFAULT_SEED, uint64_t p_inc = DEFAULT_INC);
_FORCE_INLINE_ void seed(uint64_t p_seed) {
current_seed = p_seed;
pcg.state = p_seed;
pcg32_random_r(&pcg); // Force changing internal state to avoid initial 0
pcg32_srandom_r(&pcg, current_seed, current_inc);
}
_FORCE_INLINE_ uint64_t get_seed() { return current_seed; }

10
thirdparty/misc/pcg.cpp vendored
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@ -13,3 +13,13 @@ uint32_t pcg32_random_r(pcg32_random_t* rng)
uint32_t rot = oldstate >> 59u;
return (xorshifted >> rot) | (xorshifted << ((-rot) & 31));
}
// Source from http://www.pcg-random.org/downloads/pcg-c-basic-0.9.zip
void pcg32_srandom_r(pcg32_random_t* rng, uint64_t initstate, uint64_t initseq)
{
rng->state = 0U;
rng->inc = (initseq << 1u) | 1u;
pcg32_random_r(rng);
rng->state += initstate;
pcg32_random_r(rng);
}

1
thirdparty/misc/pcg.h vendored
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@ -10,5 +10,6 @@
typedef struct { uint64_t state; uint64_t inc; } pcg32_random_t;
uint32_t pcg32_random_r(pcg32_random_t* rng);
void pcg32_srandom_r(pcg32_random_t* rng, uint64_t initstate, uint64_t initseq);
#endif // RANDOM_H