Tpetra_Details_getDiagCopyWithoutOffsets_decl.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_GETDIAGCOPYWITHOUTOFFSETS_DECL_HPP
#define TPETRA_DETAILS_GETDIAGCOPYWITHOUTOFFSETS_DECL_HPP


#include "TpetraCore_config.h"
#include "Kokkos_Core.hpp"
#include "Kokkos_ArithTraits.hpp"
#include "Tpetra_Details_OrdinalTraits.hpp"
#include "Tpetra_RowMatrix_decl.hpp"
#include "Tpetra_Vector_decl.hpp"
#include <type_traits>

namespace Tpetra {
namespace Details {

template<class DiagType,
         class LocalMapType,
         class CrsMatrixType>
struct CrsMatrixGetDiagCopyFunctor {
  typedef typename LocalMapType::local_ordinal_type LO; // local ordinal type
  typedef typename LocalMapType::global_ordinal_type GO; // global ordinal type
  typedef typename CrsMatrixType::device_type device_type;
  typedef typename CrsMatrixType::value_type scalar_type;
  typedef typename CrsMatrixType::size_type offset_type;

  typedef LO value_type;

  CrsMatrixGetDiagCopyFunctor (const DiagType& D,
                               const LocalMapType& rowMap,
                               const LocalMapType& colMap,
                               const CrsMatrixType& A) :
    D_ (D), rowMap_ (rowMap), colMap_ (colMap), A_ (A)
  {}

  KOKKOS_FUNCTION void
  operator () (const LO& lclRowInd, value_type& errCount) const
  {
    const LO INV = Tpetra::Details::OrdinalTraits<LO>::invalid ();
    const scalar_type ZERO =
      Kokkos::ArithTraits<scalar_type>::zero ();

    // If the row lacks a stored diagonal entry, then its value is zero.
    D_(lclRowInd) = ZERO;
    const GO gblInd = rowMap_.getGlobalElement (lclRowInd);
    const LO lclColInd = colMap_.getLocalElement (gblInd);

    if (lclColInd != INV) {
      auto curRow = A_.rowConst (lclRowInd);

      // FIXME (mfh 12 May 2016) Use binary search when the row is
      // long enough.  findRelOffset currently lives in KokkosKernels
      // (in tpetra/kernels/src/Kokkos_Sparse_findRelOffset.hpp).
      LO offset = 0;
      const LO numEnt = curRow.length;
      for ( ; offset < numEnt; ++offset) {
        if (curRow.colidx(offset) == lclColInd) {
          break;
        }
      }

      if (offset == numEnt) {
        ++errCount;
      }
      else {
        D_(lclRowInd) = curRow.value(offset);
      }
    }
  }

private:
  DiagType D_;
  LocalMapType rowMap_;
  LocalMapType colMap_;
  CrsMatrixType A_;
};


template<class DiagType,
         class LocalMapType,
         class CrsMatrixType>
static typename LocalMapType::local_ordinal_type
getDiagCopyWithoutOffsets (const DiagType& D,
                           const LocalMapType& rowMap,
                           const LocalMapType& colMap,
                           const CrsMatrixType& A)
{
  static_assert (Kokkos::is_view<DiagType>::value,
                 "DiagType must be a Kokkos::View.");
  static_assert (static_cast<int> (DiagType::rank) == 1,
                 "DiagType must be a 1-D Kokkos::View.");
  static_assert (std::is_same<typename DiagType::value_type, typename DiagType::non_const_value_type>::value,
                 "DiagType must be a nonconst Kokkos::View.");
  typedef typename LocalMapType::local_ordinal_type LO;
  typedef typename CrsMatrixType::device_type device_type;
  typedef typename device_type::execution_space execution_space;
  typedef Kokkos::RangePolicy<execution_space, LO> policy_type;

  typedef Kokkos::View<typename DiagType::non_const_value_type*,
    typename DiagType::array_layout,
    typename DiagType::device_type,
    Kokkos::MemoryUnmanaged> diag_type;
  diag_type D_out = D;
  CrsMatrixGetDiagCopyFunctor<diag_type, LocalMapType, CrsMatrixType>
    functor (D_out, rowMap, colMap, A);
  const LO numRows = static_cast<LO> (D.extent (0));
  LO errCount = 0;
  Kokkos::parallel_reduce (policy_type (0, numRows), functor, errCount);
  return errCount;
}

template<class SC, class LO, class GO, class NT>
LO
getLocalDiagCopyWithoutOffsetsNotFillComplete ( ::Tpetra::Vector<SC, LO, GO, NT>& diag,
                                                const ::Tpetra::RowMatrix<SC, LO, GO, NT>& A,
                                                const bool debug =
#ifdef HAVE_TPETRA_DEBUG
                                                true);
#else // ! HAVE_TPETRA_DEBUG
                                                false);
#endif // HAVE_TPETRA_DEBUG

} // namespace Details
} // namespace Tpetra

#endif // TPETRA_DETAILS_GETDIAGCOPYWITHOUTOFFSETS_DECL_HPP