ArrayHandleRandomUniformReal.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_count_ArrayHandleRandomUniformReal_h
#define viskores_count_ArrayHandleRandomUniformReal_h
 
#include <viskores/cont/ArrayHandleRandomUniformBits.h>
#include <viskores/cont/ArrayHandleTransform.h>
 
namespace viskores
{
namespace cont
{
 
namespace detail
{
template <typename Real>
struct CanonicalFunctor;
 
template <>
struct CanonicalFunctor<viskores::Float64>
{
  // We take 53 bits (number of bits in mantissa in a double) from the 64 bits random source
  // and divide it by (1 << 53).
  static constexpr viskores::Float64 DIVISOR =
    static_cast<viskores::Float64>(viskores::UInt64{ 1 } << 53);
  static constexpr viskores::UInt64 MASK = (viskores::UInt64{ 1 } << 53) - viskores::UInt64{ 1 };
 
  VISKORES_EXEC_CONT
  viskores::Float64 operator()(viskores::UInt64 bits) const { return (bits & MASK) / DIVISOR; }
};
 
template <>
struct CanonicalFunctor<viskores::Float32>
{
  // We take 24 bits (number of bits in mantissa in a double) from the 64 bits random source
  // and divide it by (1 << 24).
  static constexpr viskores::Float32 DIVISOR =
    static_cast<viskores::Float32>(viskores::UInt32{ 1 } << 24);
  static constexpr viskores::UInt32 MASK = (viskores::UInt32{ 1 } << 24) - viskores::UInt32{ 1 };
 
  VISKORES_EXEC_CONT
  viskores::Float32 operator()(viskores::UInt64 bits) const { return (bits & MASK) / DIVISOR; }
};
} // detail
 
template <typename Real = viskores::Float64>
class VISKORES_ALWAYS_EXPORT ArrayHandleRandomUniformReal
  : public viskores::cont::ArrayHandleTransform<viskores::cont::ArrayHandleRandomUniformBits,
                                                detail::CanonicalFunctor<Real>>
{
public:
  using SeedType = viskores::Vec<viskores::UInt32, 1>;
 
  VISKORES_ARRAY_HANDLE_SUBCLASS(
    ArrayHandleRandomUniformReal,
    (ArrayHandleRandomUniformReal<Real>),
    (viskores::cont::ArrayHandleTransform<viskores::cont::ArrayHandleRandomUniformBits,
                                          detail::CanonicalFunctor<Real>>));
 
  explicit ArrayHandleRandomUniformReal(viskores::Id length,
                                        SeedType seed = { std::random_device{}() })
    : Superclass(viskores::cont::ArrayHandleRandomUniformBits{ length, seed },
                 detail::CanonicalFunctor<Real>{})
  {
  }
};
 
} // cont
} // viskores
#endif //viskores_count_ArrayHandleRandomUniformReal_h