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//        MueLu: A package for multigrid based preconditioning
//                  Copyright 2012 Sandia Corporation
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#ifndef MUELU_STEEPESTDESCENTSOLVER_DEF_HPP
#define MUELU_STEEPESTDESCENTSOLVER_DEF_HPP

#include <Xpetra_CrsMatrixFactory.hpp>
#include <Xpetra_CrsMatrixWrap.hpp>
#include <Xpetra_MatrixMatrix.hpp>

#include "MueLu_Constraint.hpp"
#include "MueLu_Monitor.hpp"
#include "MueLu_Utilities.hpp"

#include "MueLu_SteepestDescentSolver_decl.hpp"

namespace MueLu {

  using Teuchos::rcp_const_cast;

  template <class Scalar, class LocalOrdinal, class GlobalOrdinal, class Node>
  SteepestDescentSolver<Scalar, LocalOrdinal, GlobalOrdinal, Node>::SteepestDescentSolver(size_t Its, SC StepLength)
  : nIts_(Its), stepLength_(StepLength)
  { }

  template <class Scalar, class LocalOrdinal, class GlobalOrdinal, class Node>
  void SteepestDescentSolver<Scalar, LocalOrdinal, GlobalOrdinal, Node>::Iterate(const Matrix& Aref, const Constraint& C, const Matrix& P0, RCP<Matrix>& P) const {
    PrintMonitor m(*this, "SD iterations");

    RCP<const Matrix> A = rcpFromRef(Aref);
    RCP<Matrix> AP, G;

    Teuchos::FancyOStream& mmfancy = this->GetOStream(Statistics2);

    Teuchos::ArrayRCP<const SC> D = Utilities::GetMatrixDiagonal(*A);

    RCP<CrsMatrix> Ptmp_ = CrsMatrixFactory::Build(C.GetPattern());
    Ptmp_->fillComplete(P0.getDomainMap(), P0.getRangeMap());
    RCP<Matrix>    Ptmp  = rcp(new CrsMatrixWrap(Ptmp_));

    // Initial P0 would only be used for multiplication
    P = rcp_const_cast<Matrix>(rcpFromRef(P0));

    for (size_t k = 0; k < nIts_; k++) {
      AP = Xpetra::MatrixMatrix<Scalar, LocalOrdinal, GlobalOrdinal, Node>::Multiply(*A, false, *P, false, mmfancy, true, false);
#if 0
      // gradient = -2 A^T * A * P
      SC stepLength = 2*stepLength_;
      G = Xpetra::MatrixMatrix<Scalar, LocalOrdinal, GlobalOrdinal, Node>::Multiply(*A, true, *AP, false, true, true);
      C.Apply(*G, *Ptmp);
#else
      // gradient = - A * P
      SC stepLength = stepLength_;
      Utilities::MyOldScaleMatrix(*AP, D, true, false, false);
      C.Apply(*AP, *Ptmp);
#endif

      RCP<Matrix> newP;
      Xpetra::MatrixMatrix<Scalar, LocalOrdinal, GlobalOrdinal, Node>::TwoMatrixAdd(*Ptmp, false, -stepLength, *P, false, Teuchos::ScalarTraits<Scalar>::one(), newP, mmfancy);
      newP->fillComplete(P->getDomainMap(), P->getRangeMap() );
      P = newP;
    }
  }
}

#endif //ifndef MUELU_STEEPESTDESCENTSOLVER_DECL_HPP
