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Introduce fast and deterministic RNG #615

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Oct 8, 2023
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Introduce fast and deterministic RNG #615

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25 changes: 21 additions & 4 deletions tests/impl.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -350,10 +350,27 @@ static inline double bankersRounding(double val)
return ret;
}

static float ranf(void)
// SplitMix64 PRNG by Sebastiano Vigna, see:
// <https://xoshiro.di.unimi.it/splitmix64.c>
static uint64_t state; // the state of SplitMix64 PRNG
const double TWOPOWER64 = pow(2, 64);

#define SSE2NEON_INIT_RNG(seed) \
do { \
state = seed; \
} while (0)

static double next()
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{
uint64_t z = (state += 0x9e3779b97f4a7c15);
z = (z ^ (z >> 30)) * 0xbf58476d1ce4e5b9;
z = (z ^ (z >> 27)) * 0x94d049bb133111eb;
return z ^ (z >> 31);
}

static float ranf()
{
uint32_t ir = rand() & 0x7FFF;
return (float) ir * (1.0f / 32768.0f);
return next() / TWOPOWER64;
}

static float ranf(float low, float high)
Expand Down Expand Up @@ -11796,7 +11813,7 @@ SSE2NEONTestImpl::SSE2NEONTestImpl(void)
mTestFloatPointer2 = (float *) platformAlignedAlloc(sizeof(__m128));
mTestIntPointer1 = (int32_t *) platformAlignedAlloc(sizeof(__m128i));
mTestIntPointer2 = (int32_t *) platformAlignedAlloc(sizeof(__m128i));
srand(0);
SSE2NEON_INIT_RNG(123456);
for (uint32_t i = 0; i < MAX_TEST_VALUE; i++) {
mTestFloats[i] = ranf(-100000, 100000);
mTestInts[i] = (int32_t) ranf(-100000, 100000);
Expand Down
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