Ifpack2_DropFilter_def.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_DROPFILTER_DEF_HPP
#define IFPACK2_DROPFILTER_DEF_HPP
#include "Ifpack2_DropFilter_decl.hpp"
#include <vector>
 
#include "Tpetra_ConfigDefs.hpp"
#include "Tpetra_RowMatrix.hpp"
#include "Tpetra_Map.hpp"
#include "Tpetra_MultiVector.hpp"
#include "Tpetra_Vector.hpp"
 
namespace Ifpack2 {
 
//==========================================================================
template <class MatrixType>
DropFilter<MatrixType>::DropFilter(const Teuchos::RCP<const Tpetra::RowMatrix<Scalar, LocalOrdinal, GlobalOrdinal, Node> > &Matrix,
                                   magnitudeType DropTol)
  : A_(Matrix)
  , DropTol_(DropTol)
  , NumRows_(0)
  , NumNonzeros_(0)
  , MaxNumEntries_(0)
  , MaxNumEntriesA_(0) {
  // use this filter only on serial matrices
  if (A_->getComm()->getSize() != 1 || A_->getLocalNumRows() != A_->getGlobalNumRows()) {
    throw std::runtime_error("Ifpack2::DropFilter can be used with Comm().getSize() == 1 only. This class is a tool for Ifpack2_AdditiveSchwarz, and it is not meant to be used otherwise.");
  }
 
  // localized matrix has all the local rows of Matrix
  NumRows_ = A_->getLocalNumRows();
 
  // NodeNumEntries_ will contain the actual number of nonzeros
  // for each localized row (that is, without external nodes,
  // and always with the diagonal entry)
  NumEntries_.resize(NumRows_);
 
  // tentative value for MaxNumEntries. This is the number of
  // nonzeros in the local matrix
  MaxNumEntries_  = A_->getLocalMaxNumRowEntries();
  MaxNumEntriesA_ = A_->getLocalMaxNumRowEntries();
 
  // ExtractMyRowCopy() will use these vectors
  Kokkos::resize(Indices_, MaxNumEntries_);
  Kokkos::resize(Values_, MaxNumEntries_);
 
  size_t ActualMaxNumEntries = 0;
  for (size_t i = 0; i < NumRows_; ++i) {
    NumEntries_[i] = MaxNumEntriesA_;
    size_t Nnz, NewNnz = 0;
    A_->getLocalRowCopy(i, Indices_, Values_, Nnz);
    for (size_t j = 0; j < Nnz; ++j) {
      if (((size_t)Indices_[j] == i) || (Teuchos::ScalarTraits<Scalar>::magnitude(Values_[j]) >= DropTol_))
        NewNnz++;
    }
 
    NumNonzeros_ += NewNnz;
    NumEntries_[i] = NewNnz;
    if (NewNnz > ActualMaxNumEntries)
      ActualMaxNumEntries = NewNnz;
  }
 
  MaxNumEntries_ = ActualMaxNumEntries;
}
 
//=========================================================================
template <class MatrixType>
DropFilter<MatrixType>::~DropFilter() {}
 
//==========================================================================
template <class MatrixType>
Teuchos::RCP<const Teuchos::Comm<int> >
DropFilter<MatrixType>::getComm() const {
  return A_->getComm();
}
 
//==========================================================================
template <class MatrixType>
Teuchos::RCP<const Tpetra::Map<typename MatrixType::local_ordinal_type,
                               typename MatrixType::global_ordinal_type,
                               typename MatrixType::node_type> >
DropFilter<MatrixType>::getRowMap() const {
  return A_->getRowMap();
}
 
//==========================================================================
template <class MatrixType>
Teuchos::RCP<const Tpetra::Map<typename MatrixType::local_ordinal_type,
                               typename MatrixType::global_ordinal_type,
                               typename MatrixType::node_type> >
DropFilter<MatrixType>::getColMap() const {
  return A_->getColMap();
}
 
//==========================================================================
template <class MatrixType>
Teuchos::RCP<const Tpetra::Map<typename MatrixType::local_ordinal_type,
                               typename MatrixType::global_ordinal_type,
                               typename MatrixType::node_type> >
DropFilter<MatrixType>::getDomainMap() const {
  return A_->getDomainMap();
}
 
//==========================================================================
template <class MatrixType>
Teuchos::RCP<const Tpetra::Map<typename MatrixType::local_ordinal_type,
                               typename MatrixType::global_ordinal_type,
                               typename MatrixType::node_type> >
DropFilter<MatrixType>::getRangeMap() const {
  return A_->getRangeMap();
}
 
//==========================================================================
template <class MatrixType>
Teuchos::RCP<const Tpetra::RowGraph<typename MatrixType::local_ordinal_type,
                                    typename MatrixType::global_ordinal_type,
                                    typename MatrixType::node_type> >
DropFilter<MatrixType>::getGraph() const {
  throw std::runtime_error("Ifpack2::DropFilter: does not support getGraph.");
}
 
//==========================================================================
template <class MatrixType>
global_size_t DropFilter<MatrixType>::getGlobalNumRows() const {
  return NumRows_;
}
 
//==========================================================================
template <class MatrixType>
global_size_t DropFilter<MatrixType>::getGlobalNumCols() const {
  return NumRows_;
}
 
//==========================================================================
template <class MatrixType>
size_t DropFilter<MatrixType>::getLocalNumRows() const {
  return NumRows_;
}
 
//==========================================================================
 
template <class MatrixType>
size_t DropFilter<MatrixType>::getLocalNumCols() const {
  return NumRows_;
}
 
//==========================================================================
template <class MatrixType>
typename MatrixType::global_ordinal_type DropFilter<MatrixType>::getIndexBase() const {
  return A_->getIndexBase();
}
 
//==========================================================================
template <class MatrixType>
global_size_t DropFilter<MatrixType>::getGlobalNumEntries() const {
  return NumNonzeros_;
}
 
//==========================================================================
template <class MatrixType>
size_t DropFilter<MatrixType>::getLocalNumEntries() const {
  return NumNonzeros_;
}
 
//==========================================================================
template <class MatrixType>
size_t DropFilter<MatrixType>::getNumEntriesInGlobalRow(GlobalOrdinal /* globalRow */) const {
  throw std::runtime_error("Ifpack2::DropFilter does not implement getNumEntriesInGlobalRow.");
}
 
//==========================================================================
template <class MatrixType>
size_t DropFilter<MatrixType>::getNumEntriesInLocalRow(LocalOrdinal localRow) const {
  return NumEntries_[localRow];
}
 
//==========================================================================
template <class MatrixType>
size_t DropFilter<MatrixType>::getGlobalMaxNumRowEntries() const {
  return MaxNumEntries_;
}
 
//==========================================================================
template <class MatrixType>
size_t DropFilter<MatrixType>::getLocalMaxNumRowEntries() const {
  return MaxNumEntries_;
}
 
//==========================================================================
template <class MatrixType>
typename MatrixType::local_ordinal_type DropFilter<MatrixType>::getBlockSize() const {
  return A_->getBlockSize();
}
 
//==========================================================================
template <class MatrixType>
bool DropFilter<MatrixType>::hasColMap() const {
  return true;
}
 
//==========================================================================
template <class MatrixType>
bool DropFilter<MatrixType>::isLocallyIndexed() const {
  return A_->isLocallyIndexed();
}
 
//==========================================================================
template <class MatrixType>
bool DropFilter<MatrixType>::isGloballyIndexed() const {
  return A_->isGloballyIndexed();
}
 
//==========================================================================
template <class MatrixType>
bool DropFilter<MatrixType>::isFillComplete() const {
  return A_->isFillComplete();
}
 
//==========================================================================
template <class MatrixType>
void DropFilter<MatrixType>::
    getGlobalRowCopy(GlobalOrdinal /*GlobalRow*/,
                     nonconst_global_inds_host_view_type & /*Indices*/,
                     nonconst_values_host_view_type & /*Values*/,
                     size_t & /*NumEntries*/) const {
  throw std::runtime_error("Ifpack2::DropFilter does not implement getGlobalRowCopy.");
}
 
//==========================================================================
template <class MatrixType>
void DropFilter<MatrixType>::
    getLocalRowCopy(LocalOrdinal LocalRow,
                    nonconst_local_inds_host_view_type &Indices,
                    nonconst_values_host_view_type &Values,
                    size_t &NumEntries) const {
  TEUCHOS_TEST_FOR_EXCEPTION((LocalRow < 0 || (size_t)LocalRow >= NumRows_ || (size_t)Indices.size() < NumEntries_[LocalRow]), std::runtime_error, "Ifpack2::DropFilter::getLocalRowCopy invalid row or array size.");
 
  // Note: This function will work correctly if called by apply, say, with Indices_ and Values_ as
  // parameters.  The structure of the loop below should make that obvious.
 
  // always extract using the object Values_ and Indices_.
  // This is because I need more space than that given by
  // the user (for the external nodes)
  size_t A_NumEntries = 0;
  A_->getLocalRowCopy(LocalRow, Indices_, Values_, A_NumEntries);
 
  // loop over all nonzero elements of row MyRow,
  // and drop elements below specified threshold.
  // Also, add value to zero diagonal
  NumEntries = 0;
  for (size_t i = 0; i < A_NumEntries; ++i) {
    // if element is above specified tol, add to the
    // user's defined arrays. Check that we are not
    // exceeding allocated space. Do not drop any diagonal entry.
    if ((Indices_[i] == LocalRow) || (Teuchos::ScalarTraits<Scalar>::magnitude(Values_[i]) >= DropTol_)) {
      Values[NumEntries]  = Values_[i];
      Indices[NumEntries] = Indices_[i];
      NumEntries++;
    }
  }
}
 
//==========================================================================
template <class MatrixType>
void DropFilter<MatrixType>::getGlobalRowView(GlobalOrdinal /* GlobalRow */,
                                              global_inds_host_view_type & /*indices*/,
                                              values_host_view_type & /*values*/) const {
  throw std::runtime_error("Ifpack2::DropFilter: does not support getGlobalRowView.");
}
 
//==========================================================================
template <class MatrixType>
void DropFilter<MatrixType>::getLocalRowView(LocalOrdinal /* LocalRow */,
                                             local_inds_host_view_type & /*indices*/,
                                             values_host_view_type & /*values*/) const {
  throw std::runtime_error("Ifpack2::DropFilter: does not support getLocalRowView.");
}
 
//==========================================================================
template <class MatrixType>
void DropFilter<MatrixType>::getLocalDiagCopy(Tpetra::Vector<Scalar, LocalOrdinal, GlobalOrdinal, Node> &diag) const {
  // This is somewhat dubious as to how the maps match.
  return A_->getLocalDiagCopy(diag);
}
 
//==========================================================================
template <class MatrixType>
void DropFilter<MatrixType>::leftScale(const Tpetra::Vector<Scalar, LocalOrdinal, GlobalOrdinal, Node> & /* x */) {
  throw std::runtime_error("Ifpack2::DropFilter does not support leftScale.");
}
 
//==========================================================================
template <class MatrixType>
void DropFilter<MatrixType>::rightScale(const Tpetra::Vector<Scalar, LocalOrdinal, GlobalOrdinal, Node> & /* x */) {
  throw std::runtime_error("Ifpack2::DropFilter does not support rightScale.");
}
 
//==========================================================================
template <class MatrixType>
void DropFilter<MatrixType>::apply(const Tpetra::MultiVector<Scalar, LocalOrdinal, GlobalOrdinal, Node> &X,
                                   Tpetra::MultiVector<Scalar, LocalOrdinal, GlobalOrdinal, Node> &Y,
                                   Teuchos::ETransp mode,
                                   Scalar /* alpha */,
                                   Scalar /* beta */) const {
  // Note: This isn't AztecOO compliant.  But neither was Ifpack's version.
  // Note: The localized maps mean the matvec is trivial (and has no import)
  TEUCHOS_TEST_FOR_EXCEPTION(X.getNumVectors() != Y.getNumVectors(), std::runtime_error,
                             "Ifpack2::DropFilter::apply ERROR: X.getNumVectors() != Y.getNumVectors().");
 
  Scalar zero                                               = Teuchos::ScalarTraits<Scalar>::zero();
  Teuchos::ArrayRCP<Teuchos::ArrayRCP<const Scalar> > x_ptr = X.get2dView();
  Teuchos::ArrayRCP<Teuchos::ArrayRCP<Scalar> > y_ptr       = Y.get2dViewNonConst();
 
  Y.putScalar(zero);
  size_t NumVectors = Y.getNumVectors();
 
  for (size_t i = 0; i < NumRows_; ++i) {
    size_t Nnz;
    // Use this class's getrow to make the below code simpler
    getLocalRowCopy(i, Indices_, Values_, Nnz);
    Scalar *Values = reinterpret_cast<Scalar *>(Values_.data());
    if (mode == Teuchos::NO_TRANS) {
      for (size_t j = 0; j < Nnz; ++j)
        for (size_t k = 0; k < NumVectors; ++k)
          y_ptr[k][i] += Values[j] * x_ptr[k][Indices_[j]];
    } else if (mode == Teuchos::TRANS) {
      for (size_t j = 0; j < Nnz; ++j)
        for (size_t k = 0; k < NumVectors; ++k)
          y_ptr[k][Indices_[j]] += Values[j] * x_ptr[k][i];
    } else {  // mode==Teuchos::CONJ_TRANS
      for (size_t j = 0; j < Nnz; ++j)
        for (size_t k = 0; k < NumVectors; ++k)
          y_ptr[k][Indices_[j]] += Teuchos::ScalarTraits<Scalar>::conjugate(Values[j]) * x_ptr[k][i];
    }
  }
}
 
//==========================================================================
template <class MatrixType>
bool DropFilter<MatrixType>::hasTransposeApply() const {
  return true;
}
 
//==========================================================================
template <class MatrixType>
bool DropFilter<MatrixType>::supportsRowViews() const {
  return false;
}
 
//==========================================================================
template <class MatrixType>
typename DropFilter<MatrixType>::mag_type DropFilter<MatrixType>::getFrobeniusNorm() const {
  throw std::runtime_error("Ifpack2::DropFilter does not implement getFrobeniusNorm.");
}
 
#define IFPACK2_DROPFILTER_INSTANT(S, LO, GO, N) \
  template class Ifpack2::DropFilter<Tpetra::RowMatrix<S, LO, GO, N> >;
 
}  // namespace Ifpack2
 
#endif