AtomicArrayExecutionObject.h

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//============================================================================
//  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 vtk_m_exec_AtomicArrayExecutionObject_h
#define vtk_m_exec_AtomicArrayExecutionObject_h
 
#include <vtkm/Atomic.h>
#include <vtkm/List.h>
#include <vtkm/cont/ArrayHandle.h>
#include <vtkm/cont/DeviceAdapter.h>
 
#include <type_traits>
 
namespace vtkm
{
namespace exec
{
 
namespace detail
{
// Clang-7 as host compiler under nvcc returns types from std::make_unsigned
// that are not compatible with the vtkm::Atomic API, so we define our own
// mapping. This must exist for every entry in vtkm::cont::AtomicArrayTypeList.
template <typename>
struct MakeUnsigned;
template <>
struct MakeUnsigned<vtkm::UInt32>
{
  using type = vtkm::UInt32;
};
template <>
struct MakeUnsigned<vtkm::Int32>
{
  using type = vtkm::UInt32;
};
template <>
struct MakeUnsigned<vtkm::UInt64>
{
  using type = vtkm::UInt64;
};
template <>
struct MakeUnsigned<vtkm::Int64>
{
  using type = vtkm::UInt64;
};
template <>
struct MakeUnsigned<vtkm::Float32>
{
  using type = vtkm::UInt32;
};
template <>
struct MakeUnsigned<vtkm::Float64>
{
  using type = vtkm::UInt64;
};
 
template <typename T>
struct ArithType
{
  using type = typename MakeUnsigned<T>::type;
};
template <>
struct ArithType<vtkm::Float32>
{
  using type = vtkm::Float32;
};
template <>
struct ArithType<vtkm::Float64>
{
  using type = vtkm::Float64;
};
}
 
template <typename T>
class AtomicArrayExecutionObject
{
  // Checks if PortalType has a GetIteratorBegin() method that returns a
  // pointer.
  template <typename PortalType,
            typename PointerType = decltype(std::declval<PortalType>().GetIteratorBegin())>
  struct HasPointerAccess : public std::is_pointer<PointerType>
  {
  };
 
public:
  using ValueType = T;
 
  AtomicArrayExecutionObject() = default;
 
  VTKM_CONT AtomicArrayExecutionObject(vtkm::cont::ArrayHandle<T> handle,
                                       vtkm::cont::DeviceAdapterId device,
                                       vtkm::cont::Token& token)
    : Data{ handle.PrepareForInPlace(device, token).GetIteratorBegin() }
    , NumberOfValues{ handle.GetNumberOfValues() }
  {
    using PortalType = decltype(handle.PrepareForInPlace(device, token));
    VTKM_STATIC_ASSERT_MSG(HasPointerAccess<PortalType>::value,
                           "Source portal must return a pointer from "
                           "GetIteratorBegin().");
  }
 
  VTKM_SUPPRESS_EXEC_WARNINGS
  VTKM_EXEC
  vtkm::Id GetNumberOfValues() const { return this->NumberOfValues; }
 
  VTKM_SUPPRESS_EXEC_WARNINGS
  VTKM_EXEC
  ValueType Get(vtkm::Id index) const
  {
    // We only support 32/64 bit signed/unsigned ints, and vtkm::Atomic
    // currently only provides API for unsigned types.
    // We'll cast the signed types to unsigned to work around this.
    using APIType = typename detail::MakeUnsigned<ValueType>::type;
 
    return static_cast<T>(vtkm::AtomicLoad(reinterpret_cast<APIType*>(this->Data + index)));
  }
 
  VTKM_SUPPRESS_EXEC_WARNINGS
  VTKM_EXEC
  ValueType Add(vtkm::Id index, const ValueType& value) const
  {
    // We only support 32/64 bit signed/unsigned ints, and vtkm::Atomic
    // currently only provides API for unsigned types.
    // We'll cast the signed types to unsigned to work around this.
    // This is safe, since the only difference between signed/unsigned types
    // is how overflow works, and signed overflow is already undefined. We also
    // document that overflow is undefined for this operation.
    using APIType = typename detail::ArithType<ValueType>::type;
 
    return static_cast<T>(
      vtkm::AtomicAdd(reinterpret_cast<APIType*>(this->Data + index), static_cast<APIType>(value)));
  }
 
  VTKM_SUPPRESS_EXEC_WARNINGS
  VTKM_EXEC
  void Set(vtkm::Id index, const ValueType& value) const
  {
    // We only support 32/64 bit signed/unsigned ints, and vtkm::Atomic
    // currently only provides API for unsigned types.
    // We'll cast the signed types to unsigned to work around this.
    // This is safe, since the only difference between signed/unsigned types
    // is how overflow works, and signed overflow is already undefined. We also
    // document that overflow is undefined for this operation.
    using APIType = typename detail::MakeUnsigned<ValueType>::type;
 
    vtkm::AtomicStore(reinterpret_cast<APIType*>(this->Data + index), static_cast<APIType>(value));
  }
 
  VTKM_SUPPRESS_EXEC_WARNINGS
  VTKM_EXEC
  bool CompareExchange(vtkm::Id index, ValueType* oldValue, const ValueType& newValue) const
  {
    // We only support 32/64 bit signed/unsigned ints, and vtkm::Atomic
    // currently only provides API for unsigned types.
    // We'll cast the signed types to unsigned to work around this.
    // This is safe, since the only difference between signed/unsigned types
    // is how overflow works, and signed overflow is already undefined.
    using APIType = typename detail::MakeUnsigned<ValueType>::type;
 
    return vtkm::AtomicCompareExchange(reinterpret_cast<APIType*>(this->Data + index),
                                       reinterpret_cast<APIType*>(oldValue),
                                       static_cast<APIType>(newValue));
  }
 
private:
  ValueType* Data{ nullptr };
  vtkm::Id NumberOfValues{ 0 };
};
}
} // namespace vtkm::exec
 
#endif //vtk_m_exec_AtomicArrayExecutionObject_h