ArrayHandleRandomUniformBits.h

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//============================================================================
//  The contents of this file are covered by the Viskores license. See
//  LICENSE.txt for details.
//
//  By contributing to this file, all contributors agree to the Developer
//  Certificate of Origin Version 1.1 (DCO 1.1) as stated in DCO.txt.
//============================================================================
 
//============================================================================
//  Copyright (c) Kitware, Inc.
//  All rights reserved.
//  See LICENSE.txt for details.
//
//  This software is distributed WITHOUT ANY WARRANTY; without even
//  the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
//  PURPOSE.  See the above copyright notice for more information.
//============================================================================
#ifndef viskores_cont_ArrayHandleRandomUniformBits_h
#define viskores_cont_ArrayHandleRandomUniformBits_h
 
#include <random>
#include <viskores/cont/ArrayHandleImplicit.h>
#include <viskores/random/Philox.h>
 
namespace viskores
{
namespace cont
{
 
namespace detail
{
struct PhiloxFunctor
{
  using SeedType = viskores::Vec<viskores::UInt32, 1>;
 
  PhiloxFunctor() = default;
 
  explicit PhiloxFunctor(SeedType seed)
    : Seed(seed)
  {
  }
 
  VISKORES_EXEC_CONT
  viskores::UInt64 operator()(viskores::Id index) const
  {
    using philox_functor = viskores::random::PhiloxFunctor2x32x10;
    using counters_type = typename philox_functor::counters_type;
 
    auto idx = static_cast<viskores::UInt64>(index);
    counters_type counters{ static_cast<viskores::UInt32>(idx),
                            static_cast<viskores::UInt32>(idx >> 32) };
    counters_type result = philox_functor{}(counters, Seed);
    return static_cast<viskores::UInt64>(result[0]) |
      static_cast<viskores::UInt64>(result[1]) << 32;
  }
 
private:
  // This is logically a const, however, this make the Functor non-copyable which is required
  // by Viskores infrastructure (e.g. ArrayHandleTransform.)
  SeedType Seed;
}; // class PhiloxFunctor
} // namespace detail
 
class VISKORES_ALWAYS_EXPORT ArrayHandleRandomUniformBits
  : public viskores::cont::ArrayHandleImplicit<detail::PhiloxFunctor>
{
public:
  using SeedType = viskores::Vec<viskores::UInt32, 1>;
 
  VISKORES_ARRAY_HANDLE_SUBCLASS_NT(ArrayHandleRandomUniformBits,
                                    (viskores::cont::ArrayHandleImplicit<detail::PhiloxFunctor>));
 
  explicit ArrayHandleRandomUniformBits(viskores::Id length,
                                        SeedType seed = { std::random_device{}() })
    : Superclass(detail::PhiloxFunctor(seed), length)
  {
  }
}; // class ArrayHandleRandomUniformBits
}
} // namespace viskores::cont
 
//=============================================================================
// Specializations of serialization related classes
 
namespace viskores
{
namespace cont
{
}
} // namespace viskores::cont
#endif //viskores_cont_ArrayHandleRandomUniformBits_h