Tpetra_Details_createMirrorView.hpp

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// @HEADER
// *****************************************************************************
//          Tpetra: Templated Linear Algebra Services Package
//
// Copyright 2008 NTESS and the Tpetra contributors.
// SPDX-License-Identifier: BSD-3-Clause
// *****************************************************************************
// @HEADER

#ifndef TPETRA_DETAILS_CREATEMIRRORVIEW_HPP
#define TPETRA_DETAILS_CREATEMIRRORVIEW_HPP

#include "TpetraCore_config.h"
#include "Teuchos_Array.hpp"
#include "Teuchos_ArrayView.hpp"
#include "Tpetra_Details_OrdinalTraits.hpp"
#include "Tpetra_Details_computeOffsets.hpp"
#include "Kokkos_Core.hpp"
#include <memory>
#include <string>


namespace Tpetra {
namespace Details {

namespace Impl {

// Implementation detail of create_mirror_view_from_raw_host_array
// (see below).
template <class ValueType,
          class OutputDeviceType,
          const bool constInput = std::is_const<ValueType>::value,
          const bool sameAsHost =
              std::is_same<Kokkos::HostSpace,
                           typename OutputDeviceType::memory_space>::value>
class CreateMirrorViewFromUnmanagedHostArray {
 public:
  typedef Kokkos::View<ValueType*, OutputDeviceType> output_view_type;
  typedef Kokkos::View<ValueType*,
                       typename output_view_type::array_layout,
                       Kokkos::HostSpace>
      input_view_type;
  static output_view_type
  doIt(ValueType* inPtr,
       const size_t inSize,
       const bool copy    = true,
       const char label[] = "");
};

// Implementation detail of create_mirror_view_from_raw_host_array
// (see below).
template <class ValueType,
          class OutputDeviceType,
          const bool constInput>
class CreateMirrorViewFromUnmanagedHostArray<ValueType, OutputDeviceType, constInput, true> {
 public:
  typedef Kokkos::View<ValueType*, OutputDeviceType> output_view_type;
  typedef Kokkos::View<ValueType*, typename output_view_type::array_layout,
                       Kokkos::HostSpace>
      input_view_type;
  static output_view_type
  doIt(ValueType* inPtr,
       const size_t inSize,
       const bool /* copy */,
       const char /* label */[] = "") {
    static_assert(std::is_same<typename OutputDeviceType::memory_space,
                               Kokkos::HostSpace>::value,
                  "OutputDeviceType::memory_space must be the same as "
                  "Kokkos::HostSpace in order to use this specialization.  "
                  "Please report this bug to the Tpetra developers.");
    return output_view_type(inPtr, inSize);
  }
};

// Implementation detail of create_mirror_view_from_raw_host_array
// (see below).
template <class ValueType,
          class OutputDeviceType>
class CreateMirrorViewFromUnmanagedHostArray<ValueType, OutputDeviceType, true, false> {
 public:
  typedef Kokkos::View<ValueType*, OutputDeviceType> output_view_type;
  typedef Kokkos::View<ValueType*, typename output_view_type::array_layout,
                       Kokkos::HostSpace>
      input_view_type;
  static output_view_type
  doIt(ValueType* inPtr,
       const size_t inSize,
       const bool copy    = true,
       const char label[] = "") {
    using Kokkos::view_alloc;
    using Kokkos::WithoutInitializing;
    static_assert(std::is_const<ValueType>::value,
                  "ValueType must be const "
                  "in order to use this specialization.  Please report this "
                  "bug to the Tpetra developers.");
    static_assert(!std::is_same<typename OutputDeviceType::memory_space, Kokkos::HostSpace>::value,
                  "OutputDeviceType::memory_space must not be the same as "
                  "Kokkos::HostSpace in order to use this specialization.  "
                  "Please report this bug to the Tpetra developers.");
    input_view_type inView(inPtr, inSize);
    // ValueType is const, so we have to strip away const first.
    typedef typename output_view_type::non_const_type nc_output_view_type;
    nc_output_view_type outView_nc;
    if (!copy) {
      // Label needs to be a string and not a char*, if given as an
      // argument to Kokkos::view_alloc.  This is because view_alloc
      // also allows a raw pointer as its first argument.  See
      // https://github.com/kokkos/kokkos/issues/434.
      outView_nc = nc_output_view_type(view_alloc(std::string(label)), inSize);
    } else {
      // No need to initialize, if we're going to copy into it anyway.
      outView_nc = nc_output_view_type(view_alloc(std::string(label), WithoutInitializing), inSize);
      // DEEP_COPY REVIEW - HOST-TO-DEVICE
      using execution_space = typename nc_output_view_type::execution_space;
      Kokkos::deep_copy(execution_space(), outView_nc, inView);
    }
    return outView_nc;  // this casts back to const
  }
};

// Implementation detail of create_mirror_view_from_raw_host_array
// (see below).
template <class ValueType,
          class OutputDeviceType>
class CreateMirrorViewFromUnmanagedHostArray<ValueType, OutputDeviceType, false, false> {
 public:
  typedef Kokkos::View<ValueType*, OutputDeviceType> output_view_type;
  typedef Kokkos::View<ValueType*, typename output_view_type::array_layout,
                       Kokkos::HostSpace>
      input_view_type;
  static output_view_type
  doIt(ValueType* inPtr,
       const size_t inSize,
       const bool copy    = true,
       const char label[] = "") {
    typedef typename OutputDeviceType::memory_space out_mem_space;
    typedef typename OutputDeviceType::execution_space out_exec_space;
    static_assert(!std::is_const<ValueType>::value,
                  "ValueType must not be "
                  "const in order to use this specialization.  Please report "
                  "this bug to the Tpetra developers.");
    static_assert(!std::is_same<out_mem_space, Kokkos::HostSpace>::value,
                  "OutputDeviceType::memory_space must not be the same as "
                  "Kokkos::HostSpace in order to use this specialization.  "
                  "Please report this bug to the Tpetra developers.");
    input_view_type inView(inPtr, inSize);
    output_view_type outView =
        Kokkos::create_mirror_view(out_mem_space(), inView);
    if (copy) {
      // DEEP_COPY REVIEW - DEVICE-TO-HOSTMIRROR
      Kokkos::deep_copy(out_exec_space(), outView, inView);
    }
    return outView;
  }
};

}  // namespace Impl

template <class ValueType, class OutputDeviceType>
typename Impl::CreateMirrorViewFromUnmanagedHostArray<ValueType, OutputDeviceType>::output_view_type
create_mirror_view_from_raw_host_array(const OutputDeviceType& /* dev */,
                                       ValueType* inPtr,
                                       const size_t inSize,
                                       const bool copy    = true,
                                       const char label[] = "") {
  typedef Impl::CreateMirrorViewFromUnmanagedHostArray<ValueType, OutputDeviceType> impl_type;
  return impl_type::doIt(inPtr, inSize, copy, label);
}

}  // namespace Details
}  // namespace Tpetra

#endif  // TPETRA_DETAILS_CREATEMIRRORVIEW_HPP