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Fixes AgentRandom uniform int #411

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merged 3 commits into from
Feb 10, 2023
Merged

Fixes AgentRandom uniform int #411

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e032881
BugFix/Breaking: AgentRandom::uniform<int>() would never return max b…
Robadob Jun 30, 2020
a4248c6
BugFix: AgentRandom::uniform<float>() would return range (0, 1]
Robadob Oct 23, 2020
1509a9d
BugFix: AgentRandom::uniform<double>() would return range (0, 1]
Robadob Feb 10, 2023
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26 changes: 19 additions & 7 deletions include/flamegpu/runtime/random/AgentRandom.cuh
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
#ifndef INCLUDE_FLAMEGPU_RUNTIME_RANDOM_AGENTRANDOM_CUH_
#define INCLUDE_FLAMEGPU_RUNTIME_RANDOM_AGENTRANDOM_CUH_

#include <cassert>
#include <limits>

#include "flamegpu/detail/curand.cuh"
#include "flamegpu/detail/StaticAssert.h"
Expand All @@ -24,7 +24,7 @@ class AgentRandom {
__forceinline__ __device__ AgentRandom(detail::curandState *d_rng);
/**
* Returns a float uniformly distributed between 0.0 and 1.0.
* @note It may return from 0.0 to 1.0, where 1.0 is included and 0.0 is excluded.
* @note It may return from 0.0 to 1.0, where 0.0 is included and 1.0 is excluded.
* @note Available as float or double
*/
template<typename T>
Expand Down Expand Up @@ -69,11 +69,23 @@ __forceinline__ __device__ AgentRandom::AgentRandom(detail::curandState *d_rng)
*/
template<>
__forceinline__ __device__ float AgentRandom::uniform() const {
return curand_uniform(d_random_state);
// curand naturally generates the range (0, 1], we want [0, 1)
// https://github.com/pytorch/pytorch/blob/059aa34b124916dfd761f3cbdb5fa97d7a01fc93/aten/src/ATen/native/cuda/Distributions.cu#L71-L77
uint32_t val = curand(d_random_state); // need just bits
constexpr auto MASK = static_cast<uint32_t>((static_cast<uint64_t>(1) << std::numeric_limits<float>::digits) - 1);
constexpr auto DIVISOR = static_cast<float>(1) / (static_cast<uint32_t>(1) << std::numeric_limits<float>::digits);
return (val & MASK) * DIVISOR;
}
template<>
__forceinline__ __device__ double AgentRandom::uniform() const {
return curand_uniform_double(d_random_state);
// curand naturally generates the range (0, 1], we want [0, 1)
// Conversion of High-Period Random Numbers to Floating Point - Jurgen A Doornik
// Based on: https://www.doornik.com/research/randomdouble.pdf
const uint32_t iRan1 = curand(d_random_state);
const uint32_t iRan2 = curand(d_random_state);
constexpr double M_RAN_INVM32 = 2.32830643653869628906e-010;
constexpr double M_RAN_INVM52 = 2.22044604925031308085e-016;
return (static_cast<int>(iRan1)*M_RAN_INVM32 + (0.5 + M_RAN_INVM52 / 2) + static_cast<int>((iRan2) & 0x000FFFFF) * M_RAN_INVM52);
}

/**
Expand Down Expand Up @@ -109,7 +121,7 @@ __forceinline__ __device__ T AgentRandom::uniform(T min, T max) const {
DTHROW("Invalid arguments passed to AgentRandom::uniform(), %lld > %lld\n", static_cast<int64_t>(min), static_cast<int64_t>(max));
}
#endif
return static_cast<T>(min + (max - min) * uniform<float>());
return static_cast<T>(min + (1 + max - min) * uniform<float>());
}
template<>
__forceinline__ __device__ int64_t AgentRandom::uniform(const int64_t min, const int64_t max) const {
Expand All @@ -118,7 +130,7 @@ __forceinline__ __device__ int64_t AgentRandom::uniform(const int64_t min, const
DTHROW("Invalid arguments passed to AgentRandom::uniform(), %lld > %lld\n", static_cast<int64_t>(min), static_cast<int64_t>(max));
}
#endif
return static_cast<int64_t>(min + (max - min) * uniform<double>());
return static_cast<int64_t>(min + (1 + max - min) * uniform<double>());
}
template<>
__forceinline__ __device__ uint64_t AgentRandom::uniform(const uint64_t min, const uint64_t max) const {
Expand All @@ -127,7 +139,7 @@ __forceinline__ __device__ uint64_t AgentRandom::uniform(const uint64_t min, con
DTHROW("Invalid arguments passed to AgentRandom::uniform(), %lld > %lld\n", static_cast<int64_t>(min), static_cast<int64_t>(max));
}
#endif
return static_cast<uint64_t>(min + (max - min) * uniform<double>());
return static_cast<uint64_t>(min + (1 + max - min) * uniform<double>());
}
template<>
__forceinline__ __device__ float AgentRandom::uniform(const float min, const float max) const {
Expand Down