/*@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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// This library is free software; you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as
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// Lesser General Public License for more details.
//
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// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
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// Questions? Contact Michael A. Heroux (maherou@sandia.gov)
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*/

#ifndef IFPACK_DROPFILTER_H
#define IFPACK_DROPFILTER_H

#include "Ifpack_ConfigDefs.h"
#include "Epetra_RowMatrix.h"
#include "Teuchos_RefCountPtr.hpp"	

class Epetra_Comm;
class Epetra_Map;
class Epetra_MultiVector;
class Epetra_Import;
class Epetra_BlockMap;

//! Ifpack_DropFilter: Filter based on matrix entries.
/*!
Ifpack_DropFilter enables the dropping of all elements whose
absolute value is below a specified threshold.

A typical use is as follows:
\code
Teuchos::RefCountPtr<Epetra_RowMatrix> A;
// first localize the matrix
Ifpack_LocalFilter LocalA(A);
// drop all elements below this value
double DropTol = 1e-5;
// now create the matrix, elements below DropTol are
// not included in calls to ExtractMyRowCopy(), Multiply()
// and Apply()
Ifpack_DropFilter DropA(LocalA,DropTol)
\endcode

<P>It is supposed that Ifpack_DropFilter is used on localized matrices.

\author Marzio Sala, SNL 9214.

\data Last modified: Oct-04.

*/
class Ifpack_DropFilter : public virtual Epetra_RowMatrix {

public:
  //! Constructor.
  Ifpack_DropFilter(const Teuchos::RefCountPtr<Epetra_RowMatrix>& Matrix,
		    double DropTol);

  //! Destructor.
  virtual ~Ifpack_DropFilter() {};

  //! Returns the number of entries in MyRow.
  virtual inline int NumMyRowEntries(int MyRow, int & NumEntries) const
  {
    NumEntries = NumEntries_[MyRow];
    return(0);
  }

  //! Returns the maximum number of entries.
  virtual int MaxNumEntries() const
  {
    return(MaxNumEntries_);
  }

  virtual int ExtractMyRowCopy(int MyRow, int Length, int & NumEntries, double *Values, int * Indices) const;

  virtual int ExtractDiagonalCopy(Epetra_Vector & Diagonal) const;

  virtual int Multiply(bool TransA, const Epetra_MultiVector& X, 
		       Epetra_MultiVector& Y) const;

  virtual int Solve(bool Upper, bool Trans, bool UnitDiagonal, 
		    const Epetra_MultiVector& X,
		    Epetra_MultiVector& Y) const;

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

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

  virtual int InvRowSums(Epetra_Vector& x) const;

  virtual int LeftScale(const Epetra_Vector& x)
  {
    return(A_->LeftScale(x));
  }

  virtual int InvColSums(Epetra_Vector& x) const;

  virtual int RightScale(const Epetra_Vector& x) 
  {
    return(A_->RightScale(x));
  }

  virtual bool Filled() const
  {
    return(A_->Filled());
  }

  virtual double NormInf() const
  {
    return(-1.0);
  }

  virtual double NormOne() const
  {
    return(-1.0);
  }

  virtual int NumGlobalNonzeros() const
  {
    return(NumNonzeros_);
  }

  virtual int NumGlobalRows() const
  {
    return(NumRows_);
  }

  virtual int NumGlobalCols() const
  {
    return(NumRows_);
  }

  virtual int NumGlobalDiagonals() const
  {
    return(NumRows_);
  }

  virtual int NumMyNonzeros() const
  {
    return(NumNonzeros_);
  }

  virtual int NumMyRows() const
  {
    return(NumRows_);
  }

  virtual int NumMyCols() const
  {
    return(NumRows_);
  }

  virtual int NumMyDiagonals() const
  {
    return(NumRows_);
  }

  virtual bool LowerTriangular() const
  {
    return(false);
  }

  virtual bool UpperTriangular() const
  {
    return(false);
  }

  virtual const Epetra_Map & RowMatrixRowMap() const
  {
    return(A_->RowMatrixRowMap());
  }

  virtual const Epetra_Map & RowMatrixColMap() const
  {
    return(A_->RowMatrixColMap());
  }

  virtual const Epetra_Import * RowMatrixImporter() const
  {
    return(A_->RowMatrixImporter());
  }

  int SetUseTranspose(bool UseTranspose)
  {
    return(A_->SetUseTranspose(UseTranspose));
  }

  bool UseTranspose() const 
  {
    return(A_->UseTranspose());
  }

  bool HasNormInf() const
  {
    return(false);
  }

  const Epetra_Comm & Comm() const
  {
    return(A_->Comm());
  }

  const Epetra_Map & OperatorDomainMap() const 
  {
    return(A_->OperatorDomainMap());
  }

  const Epetra_Map & OperatorRangeMap() const 
  {
    return(A_->OperatorRangeMap());
  }

  const Epetra_BlockMap& Map() const 
  {
    return(A_->Map());
  }

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

private:

  //! Pointer to the matrix to be preconditioned.
  Teuchos::RefCountPtr<Epetra_RowMatrix> A_;
  //! Drop tolerance.
  double DropTol_;
  //! Maximum entries in each row.
  int MaxNumEntries_;
  int MaxNumEntriesA_;
  int NumRows_;
  
  //! Number of nonzeros for the dropped matrix.
  int NumNonzeros_;

  //! 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_;
  //! Label for \c this object.
  char Label_[80];
  std::vector<int> NumEntries_;

};


#endif /* IFPACK_DROPFILTER_H */