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https://gitlab.kitware.com/vtk/vtk-m
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102 lines
3.4 KiB
C++
102 lines
3.4 KiB
C++
//============================================================================
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// Copyright (c) Kitware, Inc.
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// All rights reserved.
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// See LICENSE.txt for details.
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//
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// This software is distributed WITHOUT ANY WARRANTY; without even
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// the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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// PURPOSE. See the above copyright notice for more information.
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//============================================================================
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#ifndef vtk_m_cont_ArrayHandleRandomUniformBits_h
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#define vtk_m_cont_ArrayHandleRandomUniformBits_h
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#include <random>
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#include <vtkm/cont/ArrayHandleImplicit.h>
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#include <vtkm/random/Philox.h>
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namespace vtkm
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{
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namespace cont
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{
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namespace detail
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{
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struct PhiloxFunctor
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{
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using SeedType = vtkm::Vec<vtkm::UInt32, 1>;
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PhiloxFunctor() = default;
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explicit PhiloxFunctor(SeedType seed)
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: Seed(seed)
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{
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}
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VTKM_EXEC_CONT
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vtkm::UInt64 operator()(vtkm::Id index) const
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{
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using philox_functor = vtkm::random::PhiloxFunctor2x32x10;
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using counters_type = typename philox_functor::counters_type;
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auto idx = static_cast<vtkm::UInt64>(index);
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counters_type counters{ static_cast<vtkm::UInt32>(idx), static_cast<vtkm::UInt32>(idx >> 32) };
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counters_type result = philox_functor{}(counters, Seed);
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return static_cast<vtkm::UInt64>(result[0]) | static_cast<vtkm::UInt64>(result[1]) << 32;
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}
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private:
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// This is logically a const, however, this make the Functor non-copyable which is required
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// by VTKm infrastructure (e.g. ArrayHandleTransform.)
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SeedType Seed;
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}; // class PhiloxFunctor
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} // namespace detail
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/// \brief An \c ArrayHandle that provides a source of random bits
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///
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/// \c ArrayHandleRandomUniformBits is a specialization of ArrayHandleImplicit.
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/// It takes a user supplied seed and hash it with the a given index value. The
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/// hashed value is the value of the array at that position.
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///
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/// Currently, Philox2x32x10 as described in the
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/// "Parallel Random Numbers: As Easy as 1, 2, 3," Proceedings of the
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/// International Conference for High Performance Computing, Networking,
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/// Storage and Analysis (SC11)
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/// is used as the hash function.
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///
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/// Note: In contrast to traditional random number generator,
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/// ArrayHandleRandomUniformBits does not have "state", i.e. multiple calls
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/// the Get() method with the same index will always return the same hash value.
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/// To ge a new set of random bits, create a new ArrayHandleRandomUniformBits
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/// with a different seed.
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class VTKM_ALWAYS_EXPORT ArrayHandleRandomUniformBits
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: public vtkm::cont::ArrayHandleImplicit<detail::PhiloxFunctor>
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{
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public:
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using SeedType = vtkm::Vec<vtkm::UInt32, 1>;
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VTKM_ARRAY_HANDLE_SUBCLASS_NT(ArrayHandleRandomUniformBits,
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(vtkm::cont::ArrayHandleImplicit<detail::PhiloxFunctor>));
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/// The type of seed is specifically designed to be an vtkm::Vec<> to provide
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/// type safety for the parameters so user will not transpose two integer parameters.
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explicit ArrayHandleRandomUniformBits(vtkm::Id length, SeedType seed = { std::random_device{}() })
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: Superclass(detail::PhiloxFunctor(seed), length)
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{
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}
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}; // class ArrayHandleRandomUniformBits
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}
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} // namespace vtkm::cont
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//=============================================================================
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// Specializations of serialization related classes
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/// @cond SERIALIZATION
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namespace vtkm
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{
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namespace cont
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{
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}
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} // namespace vtkm::cont
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/// @endcond
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#endif //vtk_m_cont_ArrayHandleRandomUniformBits_h
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