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https://gitlab.kitware.com/vtk/vtk-m
synced 2024-10-05 01:49:02 +00:00
Change auto seed behavior in PerlinNoise source
The PerlinNoise source has a mode where if a seed is not set, it will choose a new seed every time it is executed. It did this by using the value 0 as an indicator to do this (and initializing the Seed to 0). However, there was a problem with one of the benchmarks that was specifically setting the seed to 0 and getting unexpected results. Fix the problem by adding a separate, hidden member of the PerlinNoise class that keeps track of whether to generate new seeds or not.
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@ -128,7 +128,7 @@ struct PerlinNoiseWorklet : public vtkm::worklet::WorkletVisitPointsWithCells
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class PerlinNoiseField : public vtkm::filter::FilterField
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{
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public:
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VTKM_CONT PerlinNoiseField(vtkm::IdComponent tableSize, vtkm::Id seed)
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VTKM_CONT PerlinNoiseField(vtkm::IdComponent tableSize, vtkm::IdComponent seed)
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: TableSize(tableSize)
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, Seed(seed)
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{
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@ -149,26 +149,7 @@ private:
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VTKM_CONT void GeneratePermutations()
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{
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std::mt19937_64 rng;
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if (this->Seed != 0)
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{
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rng.seed(this->Seed);
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}
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else
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{
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// If a seed has not been chosen, create a unique seed here. It is done here instead
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// of the `PerlinNoise` source constructor for 2 reasons. First, `std::random_device`
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// can be slow. If the user wants to specify a seed, it makes no sense to spend
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// time generating a random seed only to overwrite it. Second, creating the seed
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// here allows subsequent runs of the `PerlinNoise` source to have different random
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// results if a seed is not specified.
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//
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// It is also worth noting that the current time is added to the random number.
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// This is because the spec for std::random_device allows it to be deterministic
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// if nondeterministic hardware is unavailable and the deterministic numbers can
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// be the same for every execution of the program. Adding the current time is
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// a fallback for that case.
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rng.seed(std::random_device{}() + time(NULL));
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}
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rng.seed(this->Seed);
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std::uniform_int_distribution<vtkm::IdComponent> distribution(0, this->TableSize - 1);
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vtkm::cont::ArrayHandle<vtkm::Id> perms;
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@ -187,7 +168,7 @@ private:
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}
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vtkm::IdComponent TableSize;
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vtkm::Id Seed;
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vtkm::IdComponent Seed;
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vtkm::cont::ArrayHandle<vtkm::Id> Permutations;
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};
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@ -243,7 +224,26 @@ vtkm::cont::DataSet PerlinNoise::DoExecute() const
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auto tableSize =
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static_cast<vtkm::IdComponent>(vtkm::Max(cellDims[0], vtkm::Max(cellDims[1], cellDims[2])));
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PerlinNoiseField noiseGenerator(tableSize, this->Seed);
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vtkm::IdComponent seed = this->Seed;
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if (!this->SeedSet)
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{
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// If a seed has not been chosen, create a unique seed here. It is done here instead
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// of the `PerlinNoise` source constructor for 2 reasons. First, `std::random_device`
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// can be slow. If the user wants to specify a seed, it makes no sense to spend
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// time generating a random seed only to overwrite it. Second, creating the seed
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// here allows subsequent runs of the `PerlinNoise` source to have different random
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// results if a seed is not specified.
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//
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// It is also worth noting that the current time is added to the random number.
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// This is because the spec for std::random_device allows it to be deterministic
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// if nondeterministic hardware is unavailable and the deterministic numbers can
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// be the same for every execution of the program. Adding the current time is
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// a fallback for that case.
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seed = static_cast<vtkm::IdComponent>(std::random_device{}() + time(NULL));
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}
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PerlinNoiseField noiseGenerator(tableSize, seed);
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noiseGenerator.SetOutputFieldName("perlinnoise");
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dataSet = noiseGenerator.Execute(dataSet);
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@ -57,9 +57,13 @@ public:
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/// \brief The seed used for the pseudorandom number generation of the noise.
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///
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/// If the seed is set to 0, then a new, unique seed is picked each time `Execute` is run.
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/// If the seed is not set, then a new, unique seed is picked each time `Execute` is run.
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VTKM_CONT vtkm::IdComponent GetSeed() const { return this->Seed; }
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VTKM_CONT void SetSeed(vtkm::IdComponent seed) { this->Seed = seed; }
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VTKM_CONT void SetSeed(vtkm::IdComponent seed)
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{
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this->Seed = seed;
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this->SeedSet = true;
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}
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private:
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vtkm::cont::DataSet DoExecute() const override;
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@ -67,6 +71,7 @@ private:
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vtkm::Id3 PointDimensions = { 16, 16, 16 };
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vtkm::Vec3f Origin = { 0, 0, 0 };
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vtkm::IdComponent Seed = 0;
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bool SeedSet = false;
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};
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} //namespace source
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} //namespace vtkm
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