MueLu_UnsmooshFactory_def.hpp

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// @HEADER
// *****************************************************************************
//        MueLu: A package for multigrid based preconditioning
//
// Copyright 2012 NTESS and the MueLu contributors.
// SPDX-License-Identifier: BSD-3-Clause
// *****************************************************************************
// @HEADER

#ifndef PACKAGES_MUELU_SRC_GRAPH_MUELU_UNSMOOSHFACTORY_DEF_HPP_
#define PACKAGES_MUELU_SRC_GRAPH_MUELU_UNSMOOSHFACTORY_DEF_HPP_

#include "MueLu_Monitor.hpp"

#include "MueLu_UnsmooshFactory_decl.hpp"

namespace MueLu {

template <class Scalar, class LocalOrdinal, class GlobalOrdinal, class Node>
UnsmooshFactory<Scalar, LocalOrdinal, GlobalOrdinal, Node>::UnsmooshFactory() {}

template <class Scalar, class LocalOrdinal, class GlobalOrdinal, class Node>
RCP<const ParameterList> UnsmooshFactory<Scalar, LocalOrdinal, GlobalOrdinal, Node>::GetValidParameterList() const {
  RCP<ParameterList> validParamList = rcp(new ParameterList());
  validParamList->set<RCP<const FactoryBase> >("A", Teuchos::null, "Generating factory for unamalgamated matrix. Row map of (unamalgamted) output prolongation operator should match row map of this A.");
  validParamList->set<RCP<const FactoryBase> >("P", Teuchos::null, "Generating factory of the (amalgamated) prolongator P");
  validParamList->set<RCP<const FactoryBase> >("DofStatus", Teuchos::null, "Generating factory for dofStatus array (usually the VariableDofLaplacdianFactory)");

  validParamList->set<int>("maxDofPerNode", 1, "Maximum number of DOFs per node");
  validParamList->set<bool>("fineIsPadded", false, "true if finest level input matrix is padded");

  return validParamList;
}

template <class Scalar, class LocalOrdinal, class GlobalOrdinal, class Node>
void UnsmooshFactory<Scalar, LocalOrdinal, GlobalOrdinal, Node>::DeclareInput(Level &fineLevel, Level &coarseLevel) const {
  // const ParameterList& pL = GetParameterList();
  Input(fineLevel, "A");
  Input(coarseLevel, "P");

  // DofStatus only provided on the finest level (by user)
  // On the coarser levels it is auto-generated using the DBC information from the unamalgamated matrix A
  if (fineLevel.GetLevelID() == 0)
    Input(fineLevel, "DofStatus");
}

template <class Scalar, class LocalOrdinal, class GlobalOrdinal, class Node>
void UnsmooshFactory<Scalar, LocalOrdinal, GlobalOrdinal, Node>::Build(Level &fineLevel, Level &coarseLevel) const {
  FactoryMonitor m(*this, "Build", coarseLevel);
  typedef Teuchos::ScalarTraits<SC> STS;

  const ParameterList &pL = GetParameterList();

  // extract matrices (unamalgamated A and amalgamated P)
  RCP<Matrix> unamalgA = Get<RCP<Matrix> >(fineLevel, "A");
  RCP<Matrix> amalgP   = Get<RCP<Matrix> >(coarseLevel, "P");

  // extract user parameters
  int maxDofPerNode = pL.get<int>("maxDofPerNode");
  bool fineIsPadded = pL.get<bool>("fineIsPadded");

  // get dofStatus information
  // On the finest level it is provided by the user. On the coarser levels it is constructed
  // using the DBC information of the matrix A
  Teuchos::Array<char> dofStatus;
  if (fineLevel.GetLevelID() == 0) {
    dofStatus = Get<Teuchos::Array<char> >(fineLevel, "DofStatus");
  } else {
    // dof status is the dirichlet information of unsmooshed/unamalgamated A (fine level)
    dofStatus = Teuchos::Array<char>(unamalgA->getRowMap()->getLocalNumElements() /*amalgP->getRowMap()->getLocalNumElements() * maxDofPerNode*/, 's');

    bool bHasZeroDiagonal                  = false;
    Teuchos::ArrayRCP<const bool> dirOrNot = MueLu::Utilities<Scalar, LocalOrdinal, GlobalOrdinal, Node>::DetectDirichletRowsExt(*unamalgA, bHasZeroDiagonal, STS::magnitude(0.5));

    TEUCHOS_TEST_FOR_EXCEPTION(dirOrNot.size() != dofStatus.size(), MueLu::Exceptions::RuntimeError, "MueLu::UnsmooshFactory::Build: inconsistent number of coarse DBC array and dofStatus array. dirOrNot.size() = " << dirOrNot.size() << " dofStatus.size() = " << dofStatus.size());
    for (decltype(dirOrNot.size()) i = 0; i < dirOrNot.size(); ++i) {
      if (dirOrNot[i] == true) dofStatus[i] = 'p';
    }
  }

  // TODO: TAW the following check is invalid for SA-AMG based input prolongators
  // TEUCHOS_TEST_FOR_EXCEPTION(amalgP->getDomainMap()->isSameAs(*amalgP->getColMap()) == false, MueLu::Exceptions::RuntimeError,"MueLu::UnsmooshFactory::Build: only support for non-overlapping aggregates. (column map of Ptent must be the same as domain map of Ptent)");

  // extract CRS information from amalgamated prolongation operator
  Teuchos::ArrayRCP<const size_t> amalgRowPtr(amalgP->getLocalNumRows());
  Teuchos::ArrayRCP<const LocalOrdinal> amalgCols(amalgP->getLocalNumEntries());
  Teuchos::ArrayRCP<const Scalar> amalgVals(amalgP->getLocalNumEntries());
  Teuchos::RCP<CrsMatrix> amalgPcrs = toCrsMatrix(amalgP);
  amalgPcrs->getAllValues(amalgRowPtr, amalgCols, amalgVals);

  // calculate number of dof rows for new prolongator
  size_t paddedNrows = amalgP->getRowMap()->getLocalNumElements() * Teuchos::as<size_t>(maxDofPerNode);

  // reserve CSR arrays for new prolongation operator
  Teuchos::ArrayRCP<size_t> newPRowPtr(paddedNrows + 1);
  Teuchos::ArrayRCP<LocalOrdinal> newPCols(amalgP->getLocalNumEntries() * maxDofPerNode);
  Teuchos::ArrayRCP<Scalar> newPVals(amalgP->getLocalNumEntries() * maxDofPerNode);

  size_t rowCount = 0;  // actual number of (local) in unamalgamated prolongator
  if (fineIsPadded == true || fineLevel.GetLevelID() > 0) {
    // build prolongation operator for padded fine level matrices.
    // Note: padded fine level dofs are transferred by injection.
    // That is, these interpolation stencils do not take averages of
    // coarse level variables. Further, fine level Dirichlet points
    // also use injection.

    size_t cnt = 0;  // local id counter
    for (decltype(amalgRowPtr.size()) i = 0; i < amalgRowPtr.size() - 1; i++) {
      // determine number of entries in amalgamated dof row i
      size_t rowLength = amalgRowPtr[i + 1] - amalgRowPtr[i];

      // loop over dofs per node (unamalgamation)
      for (int j = 0; j < maxDofPerNode; j++) {
        newPRowPtr[i * maxDofPerNode + j] = cnt;
        if (dofStatus[i * maxDofPerNode + j] == 's') {  // add only "standard" dofs to unamalgamated prolongator
          // loop over column entries in amalgamated P
          for (size_t k = 0; k < rowLength; k++) {
            newPCols[cnt]   = amalgCols[k + amalgRowPtr[i]] * maxDofPerNode + j;
            newPVals[cnt++] = amalgVals[k + amalgRowPtr[i]];
          }
        }
      }
    }

    newPRowPtr[paddedNrows] = cnt;  // close row CSR array
    rowCount                = paddedNrows;
  } else {
    // Build prolongation operator for non-padded fine level matrices.
    // Need to map from non-padded dofs to padded dofs. For this, look
    // at the status array and skip padded dofs.

    size_t cnt = 0;  // local id counter

    for (decltype(amalgRowPtr.size()) i = 0; i < amalgRowPtr.size() - 1; i++) {
      // determine number of entries in amalgamated dof row i
      size_t rowLength = amalgRowPtr[i + 1] - amalgRowPtr[i];

      // loop over dofs per node (unamalgamation)
      for (int j = 0; j < maxDofPerNode; j++) {
        // no interpolation for padded fine dofs as they do not exist

        if (dofStatus[i * maxDofPerNode + j] == 's') {  // add only "standard" dofs to unamalgamated prolongator
          newPRowPtr[rowCount++] = cnt;
          // loop over column entries in amalgamated P
          for (size_t k = 0; k < rowLength; k++) {
            newPCols[cnt]   = amalgCols[k + amalgRowPtr[i]] * maxDofPerNode + j;
            newPVals[cnt++] = amalgVals[k + amalgRowPtr[i]];
          }
        }
        if (dofStatus[i * maxDofPerNode + j] == 'd') {  // Dirichlet handling
          newPRowPtr[rowCount++] = cnt;
        }
      }
    }
    newPRowPtr[rowCount] = cnt;  // close row CSR array
  }                              // fineIsPadded == false

  // generate coarse domain map
  // So far no support for gid offset or strided maps. This information
  // could be gathered easily from the unamalgamated fine level operator A.
  std::vector<size_t> stridingInfo(1, maxDofPerNode);

  GlobalOrdinal nCoarseDofs      = amalgP->getDomainMap()->getLocalNumElements() * maxDofPerNode;
  GlobalOrdinal indexBase        = amalgP->getDomainMap()->getIndexBase();
  RCP<const Map> coarseDomainMap = StridedMapFactory::Build(amalgP->getDomainMap()->lib(),
                                                            Teuchos::OrdinalTraits<Xpetra::global_size_t>::invalid(),
                                                            nCoarseDofs,
                                                            indexBase,
                                                            stridingInfo,
                                                            amalgP->getDomainMap()->getComm(),
                                                            -1 /* stridedBlockId */,
                                                            0 /*domainGidOffset */);

  size_t nColCoarseDofs = Teuchos::as<size_t>(amalgP->getColMap()->getLocalNumElements() * maxDofPerNode);
  Teuchos::Array<GlobalOrdinal> unsmooshColMapGIDs(nColCoarseDofs);
  for (size_t c = 0; c < amalgP->getColMap()->getLocalNumElements(); ++c) {
    GlobalOrdinal gid = (amalgP->getColMap()->getGlobalElement(c) - indexBase) * maxDofPerNode + indexBase;

    for (int i = 0; i < maxDofPerNode; ++i) {
      unsmooshColMapGIDs[c * maxDofPerNode + i] = gid + i;
    }
  }
  Teuchos::RCP<Map> coarseColMap = MapFactory::Build(amalgP->getDomainMap()->lib(),
                                                     Teuchos::OrdinalTraits<Xpetra::global_size_t>::invalid(),
                                                     unsmooshColMapGIDs(),  // View,
                                                     indexBase,
                                                     amalgP->getDomainMap()->getComm());

  // Assemble unamalgamated P
  Teuchos::RCP<CrsMatrix> unamalgPCrs = CrsMatrixFactory::Build(unamalgA->getRowMap(),
                                                                coarseColMap,
                                                                maxDofPerNode * amalgP->getLocalMaxNumRowEntries());
  for (size_t i = 0; i < rowCount; i++) {
    unamalgPCrs->insertLocalValues(i,
                                   newPCols.view(newPRowPtr[i], newPRowPtr[i + 1] - newPRowPtr[i]),
                                   newPVals.view(newPRowPtr[i], newPRowPtr[i + 1] - newPRowPtr[i]));
  }
  unamalgPCrs->fillComplete(coarseDomainMap, unamalgA->getRowMap());

  Teuchos::RCP<Matrix> unamalgP = Teuchos::rcp(new CrsMatrixWrap(unamalgPCrs));

  Set(coarseLevel, "P", unamalgP);
}

}  // namespace MueLu

#endif /* PACKAGES_MUELU_SRC_GRAPH_MUELU_UNSMOOSHFACTORY_DEF_HPP_ */