Ifpack2_CreateOverlapGraph.hpp

// @HEADER
// *****************************************************************************
//       Ifpack2: Templated Object-Oriented Algebraic Preconditioner Package
//
// Copyright 2009 NTESS and the Ifpack2 contributors.
// SPDX-License-Identifier: BSD-3-Clause
// *****************************************************************************
// @HEADER

#ifndef IFPACK2_CREATEOVERLAPGRAPH_HPP
#define IFPACK2_CREATEOVERLAPGRAPH_HPP

#include "Ifpack2_ConfigDefs.hpp"
#include "Tpetra_CrsGraph.hpp"
#include "Tpetra_CrsMatrix.hpp"
#include "Tpetra_Import.hpp"
#include "Teuchos_RefCountPtr.hpp"

namespace Ifpack2 {

template <class GraphType>
Teuchos::RCP<const GraphType>
createOverlapGraph(const Teuchos::RCP<const GraphType>& inputGraph,
                   const int overlapLevel) {
  using Teuchos::RCP;
  using Teuchos::rcp;
  typedef Tpetra::Map<typename GraphType::local_ordinal_type,
                      typename GraphType::global_ordinal_type,
                      typename GraphType::node_type>
      map_type;
  typedef Tpetra::Import<typename GraphType::local_ordinal_type,
                         typename GraphType::global_ordinal_type,
                         typename GraphType::node_type>
      import_type;
  TEUCHOS_TEST_FOR_EXCEPTION(
      overlapLevel < 0, std::invalid_argument,
      "Ifpack2::createOverlapGraph: overlapLevel must be >= 0, "
      "but you specified overlapLevel = "
          << overlapLevel << ".");

  const int numProcs = inputGraph->getMap()->getComm()->getSize();
  if (overlapLevel == 0 || numProcs < 2) {
    return inputGraph;
  }

  RCP<const map_type> overlapRowMap = inputGraph->getRowMap();
  RCP<const map_type> domainMap     = inputGraph->getDomainMap();
  RCP<const map_type> rangeMap      = inputGraph->getRangeMap();

  RCP<GraphType> overlapGraph;
  RCP<const GraphType> oldGraph;
  RCP<const map_type> oldRowMap;
  for (int level = 0; level < overlapLevel; ++level) {
    oldGraph  = overlapGraph;
    oldRowMap = overlapRowMap;

    RCP<const import_type> overlapImporter;
    if (level == 0) {
      overlapImporter = inputGraph->getImporter();
    } else {
      overlapImporter = oldGraph->getImporter();
    }

    overlapRowMap = overlapImporter->getTargetMap();
    if (level < overlapLevel - 1) {
      overlapGraph = rcp(new GraphType(overlapRowMap, 0));
    } else {
      // On last iteration, we want to filter out all columns except those that
      // correspond to rows in the graph.  This ensures that our graph is square
      overlapGraph = rcp(new GraphType(overlapRowMap, overlapRowMap, 0));
    }

    overlapGraph->doImport(*inputGraph, *overlapImporter, Tpetra::INSERT);
    overlapGraph->fillComplete(domainMap, rangeMap);
  }

  return overlapGraph;
}

template <class MatrixType>
Teuchos::RCP<const MatrixType>
createOverlapMatrix(const Teuchos::RCP<const MatrixType>& inputMatrix,
                    const int overlapLevel) {
  using Teuchos::RCP;
  using Teuchos::rcp;
  typedef typename MatrixType::map_type map_type;
  typedef Tpetra::Import<typename MatrixType::local_ordinal_type,
                         typename MatrixType::global_ordinal_type,
                         typename MatrixType::node_type>
      import_type;

  TEUCHOS_TEST_FOR_EXCEPTION(
      overlapLevel < 0, std::invalid_argument,
      "Ifpack2::createOverlapMatrix: overlapLevel must be >= 0, "
      "but you specified overlapLevel = "
          << overlapLevel << ".");

  const int numProcs = inputMatrix->getMap()->getComm()->getSize();
  if (overlapLevel == 0 || numProcs < 2) {
    return inputMatrix;
  }

  RCP<const map_type> overlapRowMap = inputMatrix->getRowMap();
  RCP<const map_type> domainMap     = inputMatrix->getDomainMap();
  RCP<const map_type> rangeMap      = inputMatrix->getRangeMap();

  RCP<MatrixType> overlapMatrix;
  RCP<const MatrixType> oldMatrix;
  RCP<const map_type> oldRowMap;
  for (int level = 0; level < overlapLevel; ++level) {
    oldMatrix = overlapMatrix;
    oldRowMap = overlapRowMap;

    RCP<const import_type> overlapImporter;
    if (level == 0) {
      overlapImporter = inputMatrix->getGraph()->getImporter();
    } else {
      overlapImporter = oldMatrix->getGraph()->getImporter();
    }

    overlapRowMap = overlapImporter->getTargetMap();
    if (level < overlapLevel - 1) {
      overlapMatrix = rcp(new MatrixType(overlapRowMap, 0));
    } else {
      // On last iteration, we want to filter out all columns except those that
      // correspond to rows in the matrix.  This assures that our matrix is square
      overlapMatrix = rcp(new MatrixType(overlapRowMap, overlapRowMap, 0));
    }

    overlapMatrix->doImport(*inputMatrix, *overlapImporter, Tpetra::INSERT);
    overlapMatrix->fillComplete(domainMap, rangeMap);
  }

  return overlapMatrix;
}

}  // namespace Ifpack2

#endif  // IFPACK2_CREATEOVERLAPGRAPH_HPP