/*@HEADER
// ***********************************************************************
//
//       Ifpack: Object-Oriented Algebraic Preconditioner Package
//                 Copyright (2002) Sandia Corporation
//
// Under terms of Contract DE-AC04-94AL85000, there is a non-exclusive
// license for use of this work by or on behalf of the U.S. Government.
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#ifndef IFPACK_LOCALFILTER_H
#define IFPACK_LOCALFILTER_H

#include "Ifpack_ConfigDefs.h"
#ifdef HAVE_MPI
#include "Epetra_MpiComm.h"
#else
#include "Epetra_SerialComm.h"
#endif
#include "Epetra_RowMatrix.h"
#include "Teuchos_RefCountPtr.hpp"

class Epetra_Map;
class Epetra_MultiVector;
class Epetra_Vector;
class Epetra_Import;
class Epetra_BlockMap;

//! Ifpack_LocalFilter a class for light-weight extraction of the submatrix corresponding to local rows and columns.

/*! Class Ifpack_LocalFilter enables a light-weight contruction of an
 Epetra_RowMatrix-derived object, containing only the elements of the original, 
 distributed matrix with local row and column ID. The local
 submatrix is based on a communicator containing the local process only. 
 Each process will have its local object, corresponding to the local submatrix.
 Submatrices may or may not overlap.
 
 The following instructions can be used to create "localized" matrices:
 \code
 #include "Ifpack_LocalFilter.h"
 ...
 Teuchos::RefCountPtr<Epetra_RowMatrix> A;             // fill the elements of A,
 A->FillComplete();

 Ifpack_LocalFilter LocalA(A);
 \endcode

 Once created, \c LocalA defined, on each process, the submatrix 
 corresponding to local rows and columns only. The creation 
 and use of
 \c LocalA is "cheap", as the elements of the local matrix are
 obtained through calls to ExtractMyRowCopy on the original, distributed
 matrix, say A. This means that \c A must remain in scope every time 
 \c LocalA is accessed.

 A very convenient use of this class is to use Ifpack solvers to
 compute the LU factorizations of local blocks. If applied to
 a localized matrix, several Ifpack objects can operator in the same
 phase in a safe way, without non-required data exchange.

 \author Marzio Sala, SNL 9214

 \date Sep-04
 
 */ 
class Ifpack_LocalFilter : public virtual Epetra_RowMatrix {

public:
  //@{ \name Constructor.
  //! Constructor
  Ifpack_LocalFilter(const Teuchos::RefCountPtr<const Epetra_RowMatrix>& Matrix);

  //@}
  //@{ \name Destructor.
  //! Destructor
  virtual ~Ifpack_LocalFilter() {};

  //@}

  //@{ \name Matrix data extraction routines

  //! Returns the number of nonzero entries in MyRow.
  /*! 
    \param 
    MyRow - (In) Local row.
    \param 
    NumEntries - (Out) Number of nonzero values present.

    \return Integer error code, set to 0 if successful.
    */
  virtual int NumMyRowEntries(int MyRow, int & NumEntries) const
  {
    NumEntries = NumEntries_[MyRow];
    return(0);
  }

  //! Returns the maximum of NumMyRowEntries() over all rows.
  virtual int MaxNumEntries() const
  {
    return(MaxNumEntries_);
  }

  //! Returns a copy of the specified local row in user-provided arrays.
  /*! 
    \param
    MyRow - (In) Local row to extract.
    \param
    Length - (In) Length of Values and Indices.
    \param
    NumEntries - (Out) Number of nonzero entries extracted.
    \param
    Values - (Out) Extracted values for this row.
    \param 
    Indices - (Out) Extracted global column indices for the corresponding values.

    \return Integer error code, set to 0 if successful.
    */
  virtual inline int ExtractMyRowCopy(int MyRow, int Length, int & NumEntries, double *Values, int * Indices) const;

  //! Returns a copy of the main diagonal in a user-provided vector.
  /*! 
    \param
    Diagonal - (Out) Extracted main diagonal.

    \return Integer error code, set to 0 if successful.
    */
  virtual int ExtractDiagonalCopy(Epetra_Vector & Diagonal) const;
  //@}

  //@{ \name Mathematical functions.

  //! Returns the result of a Epetra_RowMatrix multiplied by a Epetra_MultiVector X in Y.
  /*! 
    \param 
    TransA -(In) If true, multiply by the transpose of matrix, otherwise just use matrix.
    \param 
    X - (In) A Epetra_MultiVector of dimension NumVectors to multiply with matrix.
    \param 
    Y -(Out) A Epetra_MultiVector of dimension NumVectorscontaining result.

    \return Integer error code, set to 0 if successful.
    */
  virtual int Multiply(bool TransA, const Epetra_MultiVector& X, Epetra_MultiVector& Y) const
  {
    if (TransA == true) {
      IFPACK_CHK_ERR(-1);
    }

    IFPACK_CHK_ERR(Apply(X,Y));
    return(0);
  }

  //! Returns result of a local-only solve using a triangular Epetra_RowMatrix with Epetra_MultiVectors X and Y (NOT IMPLEMENTED).
  virtual int Solve(bool Upper, bool Trans, bool UnitDiagonal, const Epetra_MultiVector& X, 
		    Epetra_MultiVector& Y) const
  {
    IFPACK_RETURN(-1); // not implemented 
  }

  virtual int Apply(const Epetra_MultiVector& X,
		    Epetra_MultiVector& Y) const;

  virtual int ApplyInverse(const Epetra_MultiVector& X,
			   Epetra_MultiVector& Y) const;
  //! Computes the sum of absolute values of the rows of the Epetra_RowMatrix, results returned in x (NOT IMPLEMENTED).
  virtual int InvRowSums(Epetra_Vector& x) const
  {
    IFPACK_RETURN(-1); // not implemented
  }

  //! Scales the Epetra_RowMatrix on the left with a Epetra_Vector x (NOT IMPLEMENTED).
  virtual int LeftScale(const Epetra_Vector& x)
  {
    IFPACK_RETURN(-1); // not implemented
  }

  //! Computes the sum of absolute values of the columns of the Epetra_RowMatrix, results returned in x (NOT IMPLEMENTED).
  virtual int InvColSums(Epetra_Vector& x) const
  {
    IFPACK_RETURN(-1); // not implemented
  }


  //! Scales the Epetra_RowMatrix on the right with a Epetra_Vector x (NOT IMPLEMENTED).
  virtual int RightScale(const Epetra_Vector& x) 
  {
    IFPACK_RETURN(-1); // not implemented
  }

  //@}

  //@{ \name Atribute access functions

  //! If FillComplete() has been called, this query returns true, otherwise it returns false.
  virtual bool Filled() const
  {
    return true;
  }

  //! Returns the infinity norm of the global matrix.
  /* Returns the quantity \f$ \| A \|_\infty\f$ such that
     \f[\| A \|_\infty = \max_{1\lei\len} \sum_{i=1}^m |a_{ij}| \f].
     */ 
  virtual double NormInf() const
  {
    return(-1.0);
  }

  //! Returns the one norm of the global matrix.
  /* Returns the quantity \f$ \| A \|_1\f$ such that
     \f[\| A \|_1= \max_{1\lej\len} \sum_{j=1}^n |a_{ij}| \f].
     */ 
  virtual double NormOne() const
  {
    IFPACK_RETURN(-1.0);
  }

  //! Returns the number of nonzero entries in the global matrix.
  virtual int NumGlobalNonzeros() const
  {
    return(NumNonzeros_);
  }

  //! Returns the number of global matrix rows.
  virtual int NumGlobalRows() const
  {
    return(NumRows_);
  }

  //! Returns the number of global matrix columns.
  virtual int NumGlobalCols() const
  {
    return(NumRows_);
  }

  //! Returns the number of global nonzero diagonal entries, based on global row/column index comparisons.
  virtual int NumGlobalDiagonals() const
  {
    return(NumRows_);
  }

  //! Returns the number of nonzero entries in the calling processor's portion of the matrix.
  virtual int NumMyNonzeros() const
  {
    return(NumNonzeros_);
  }

  //! Returns the number of matrix rows owned by the calling processor.
  virtual int NumMyRows() const
  {
    return(NumRows_);
  }

  //! Returns the number of matrix columns owned by the calling processor.
  virtual int NumMyCols() const
  {
    return(NumRows_);
  }

  //! Returns the number of local nonzero diagonal entries, based on global row/column index comparisons.
  virtual int NumMyDiagonals() const
  {
    return(NumRows_);
  }

  //! If matrix is lower triangular in local index space, this query returns true, otherwise it returns false.
  virtual bool LowerTriangular() const
  {
    return(Matrix_->LowerTriangular());
  }

  //! If matrix is upper triangular in local index space, this query returns true, otherwise it returns false.
  virtual bool UpperTriangular() const
  {
    return(Matrix_->UpperTriangular());
  }

  //! Returns the Epetra_Map object associated with the rows of this matrix.
  virtual const Epetra_Map & RowMatrixRowMap() const
  {
    return(*Map_);
  }

  //! Returns the Epetra_Map object associated with the columns of this matrix.
  virtual const Epetra_Map & RowMatrixColMap() const
  {
    return(*Map_);
  }

  //! Returns the Epetra_Import object that contains the import operations for distributed operations.
  virtual const Epetra_Import * RowMatrixImporter() const
  {
    return(0);
  }
  //@}

  // following functions are required to derive Epetra_RowMatrix objects.

  //! Sets ownership.
  int SetOwnership(bool ownership)
  {
    IFPACK_RETURN(-1);
  }

  //! Sets use transpose (not implemented).
  int SetUseTranspose(bool UseTranspose_in)
  {
    UseTranspose_ = UseTranspose_in;
    return(0);
  }

  //! Returns the current UseTranspose setting.
  bool UseTranspose() const 
  {
    return(UseTranspose_);
  }

  //! Returns true if the \e this object can provide an approximate Inf-norm, false otherwise.
  bool HasNormInf() const
  {
    return(false);
  }

  //! Returns a pointer to the Epetra_Comm communicator associated with this operator.
  const Epetra_Comm & Comm() const
  {
    return(*SerialComm_);
  }

  //! Returns the Epetra_Map object associated with the domain of this operator.
  const Epetra_Map & OperatorDomainMap() const 
  {
    return(*Map_);
  }

  //! Returns the Epetra_Map object associated with the range of this operator.
  const Epetra_Map & OperatorRangeMap() const 
  {
    return(*Map_);
  }
  //@}

const Epetra_BlockMap& Map() const;

const char* Label() const{
  return(Label_);
};

private:

  //! Pointer to the matrix to be preconditioned.
  Teuchos::RefCountPtr<const Epetra_RowMatrix> Matrix_;
#ifdef HAVE_MPI
  //! Communicator containing this process only.
  Teuchos::RefCountPtr<Epetra_MpiComm> SerialComm_;
#else
  //! Communicator containing this process only.
  Teuchos::RefCountPtr<Epetra_SerialComm> SerialComm_;
#endif
  //! Map based on SerialComm_, containing the local rows only.
  Teuchos::RefCountPtr<Epetra_Map> Map_;
  //! Number of rows in the local matrix.
  int NumRows_;
  //! Number of nonzeros in the local matrix.
  int NumNonzeros_;
  //! Maximum number of nonzero entries in a row for the filtered matrix.
  int MaxNumEntries_;
  //! Maximum number of nonzero entries in a row for Matrix_.
  int MaxNumEntriesA_;
  //! NumEntries_[i] contains the nonzero entries in row `i'.
  std::vector<int> NumEntries_;
  //! Used in ExtractMyRowCopy, to avoid allocation each time.
  mutable std::vector<int> Indices_;
  //! Used in ExtractMyRowCopy, to avoid allocation each time.
  mutable std::vector<double> Values_;
  //! If true, the tranpose of the local matrix will be used.
  bool UseTranspose_;
  //! Label for \c this object.
  char Label_[80];
  Teuchos::RefCountPtr<Epetra_Vector> Diagonal_;
  double NormOne_;
  double NormInf_;

};

#endif /* IFPACK_LOCALFILTER_H */