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Merge pull request #27171 from Chaosus/randfix

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Properly setup seed in RNG
This commit is contained in:
Rémi Verschelde 2019-04-01 17:17:30 +02:00 committed by GitHub
commit 29a1202d39
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GPG key ID: 4AEE18F83AFDEB23
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) : RandomPCG::RandomPCG(uint64_t p_seed, uint64_t p_inc) :
pcg(), pcg(),
current_seed(DEFAULT_SEED) { current_inc(p_inc) {
pcg.inc = p_inc;
seed(p_seed); seed(p_seed);
} }

6
core/math/random_pcg.h
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@ -38,18 +38,18 @@
class RandomPCG { class RandomPCG {
pcg32_random_t pcg; pcg32_random_t pcg;
uint64_t current_seed; // seed with this to get the same state uint64_t current_seed; // seed with this to get the same state
uint64_t current_inc;
public: public:
static const uint64_t DEFAULT_SEED = 12047754176567800795U; static const uint64_t DEFAULT_SEED = 12047754176567800795U;
static const uint64_t DEFAULT_INC = PCG_DEFAULT_INC_64; static const uint64_t DEFAULT_INC = PCG_DEFAULT_INC_64;
static const uint64_t RANDOM_MAX = 0xFFFFFFFF; 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) { _FORCE_INLINE_ void seed(uint64_t p_seed) {
current_seed = p_seed; current_seed = p_seed;
pcg.state = p_seed; pcg32_srandom_r(&pcg, current_seed, current_inc);
pcg32_random_r(&pcg); // Force changing internal state to avoid initial 0
} }
_FORCE_INLINE_ uint64_t get_seed() { return current_seed; } _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; uint32_t rot = oldstate >> 59u;
return (xorshifted >> rot) | (xorshifted << ((-rot) & 31)); 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
View file

@ -10,5 +10,6 @@
typedef struct { uint64_t state; uint64_t inc; } pcg32_random_t; typedef struct { uint64_t state; uint64_t inc; } pcg32_random_t;
uint32_t pcg32_random_r(pcg32_random_t* rng); 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 #endif // RANDOM_H