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//       Ifpack: Object-Oriented Algebraic Preconditioner Package
//                 Copyright (2002) Sandia Corporation
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#ifndef IFPACK_CHEBYSHEV_H
#define IFPACK_CHEBYSHEV_H

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

namespace Teuchos {
  class ParameterList;
}

class Epetra_MultiVector;
class Epetra_Vector;
class Epetra_Map;
class Epetra_Comm;
class Epetra_Time;
class Epetra_Vector;
class Epetra_Operator;
class Epetra_RowMatrix;

//! Ifpack_Chebyshev: class for preconditioning with Chebyshev polynomials in Ifpack

/*!
  The Ifpack_Chebyshev class enables the construction of preconditioners
  based on Chebyshev polynomials for an Epetra_RowMatrix.
  Ifpack_Chebyshev is derived from the Ifpack_Preconditioner class, 
  which is itself derived from Epetra_Operator.
  Therefore this object can be used as preconditioner everywhere an
  ApplyInverse() method is required in the preconditioning step.

  The class is an adaptation of the routine ML_Cheby in Smoother/ml_smoother.h

<P> (04/04/06) Flops are not counted in the routine ApplyInverse()

<P> (04/04/06) The switch to use the transpose matrix is not used in ApplyInverse()

The list of parameters is
- EigRatio_             = List.get("chebyshev: ratio eigenvalue", EigRatio_);
this is the ratio to define the lower bound on the spectrum; lambda^* = LambdaMax_ / EigRatio_;
a typical value used in ML is 30.0 (30.0 is the default value).
- LambdaMin_            = List.get("chebyshev: min eigenvalue", LambdaMin_);
this is the smallest eigenvalue; this parameter is optional and is only
accessed to check whether the input matrix is equal to identity.
- LambdaMax_            = List.get("chebyshev: max eigenvalue", LambdaMax_);
this is the largest eigenvalue of the matrix.
- PolyDegree_           = List.get("chebyshev: degree",PolyDegree_);
this is the polynomial degree.
- MinDiagonalValue_     = List.get("chebyshev: min diagonal value", MinDiagonalValue_);
this defines the threshold for diagonal values under which they are not inverted
- ZeroStartingSolution_ = List.get("chebyshev: zero starting solution", ZeroStartingSolution_);
this flag allows to set a non-zero initial guess.

\author Ulrich Hetmaniuk. SNL 1414.

\date Last modified on 04-Apr-06.
*/

class Ifpack_Chebyshev : public Ifpack_Preconditioner {

public:

  //@{ \name Constructors/Destructors
  //! Ifpack_Chebyshev constructor with given Epetra_Operator/Epetra_RowMatrix.
  /*! Creates an instance of Ifpack_Chebyshev class.
   *
   * \param
   * Matrix - (In) Pointer to the operator to precondition.
   */
  Ifpack_Chebyshev(const Epetra_Operator* Matrix);

  //! Ifpack_Chebyshev constructor with given Epetra_Operator/Epetra_RowMatrix.
  /*! Creates an instance of Ifpack_Chebyshev class.
   *
   * \param
   * Matrix - (In) Pointer to the matrix to precondition.
   */
  Ifpack_Chebyshev(const Epetra_RowMatrix* Matrix);

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

  //@}

  /*! This flag can be used to apply the preconditioner to the transpose of
   * the input operator. 
   * 
   * \return Integer error code, set to 0 if successful.  
   * Set to -1 if this implementation does not support transpose.
    */
  virtual inline int SetUseTranspose(bool UseTranspose_in)
  {
    UseTranspose_ = UseTranspose_in;
    return(0);
  }

  //@}

  //@{ \name Mathematical functions.

  //! Applies the matrix to an Epetra_MultiVector.
  /*! 
    \param 
    X - (In) A Epetra_MultiVector of dimension NumVectors to multiply with matrix.
    \param 
    Y - (Out) A Epetra_MultiVector of dimension NumVectors containing the result.

    \return Integer error code, set to 0 if successful.
    */
  virtual inline int Apply(const Epetra_MultiVector& X, Epetra_MultiVector& Y) const;

  //! Applies the preconditioner to X, returns the result in Y.
  /*! 
    \param
    X - (In) A Epetra_MultiVector of dimension NumVectors to be preconditioned.
    \param
    Y - (InOut) A Epetra_MultiVector of dimension NumVectors containing result.

    \return Integer error code, set to 0 if successful.

    \warning This routine is NOT AztecOO complaint.
    */
  virtual int ApplyInverse(const Epetra_MultiVector& X, Epetra_MultiVector& Y) const;

  //! Returns the infinity norm of the global matrix (not implemented)
  virtual double NormInf() const
  {
    return(-1.0);
  }
  //@}

  //@{ \name Atribute access functions

  virtual const char * Label() const
  {
    return(Label_.c_str());
  }

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

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

  //! Returns a pointer to the Epetra_Comm communicator associated with this operator.
  virtual const Epetra_Comm & Comm() const;

  //! Returns the Epetra_Map object associated with the domain of this operator.
  virtual const Epetra_Map & OperatorDomainMap() const;

  //! Returns the Epetra_Map object associated with the range of this operator.
  virtual const Epetra_Map & OperatorRangeMap() const;

  virtual int Initialize();
  
  virtual bool IsInitialized() const
  {
    return(IsInitialized_);
  }

  //! Returns \c true if the preconditioner has been successfully computed.
  virtual inline bool IsComputed() const
  {
    return(IsComputed_);
  }

  //! Computes the preconditioners.
  virtual int Compute();

  //@}
 
  //@{ \name Miscellaneous

  virtual const Epetra_RowMatrix& Matrix() const 
  {
    return(*Matrix_);
  }

  //! Computes the condition number estimates and returns the value.
  virtual double Condest(const Ifpack_CondestType CT = Ifpack_Cheap,
                         const int MaxIters = 1550,
                         const double Tol = 1e-9,
                         Epetra_RowMatrix* Matrix_in = 0);

  //! Returns the condition number estimate, or -1.0 if not computed.
  virtual double Condest() const
  {
    return(Condest_);
  }

  //! Sets all the parameters for the preconditioner
  virtual int SetParameters(Teuchos::ParameterList& List);

  //! Prints object to an output stream
  virtual ostream& Print(ostream & os) const;

  //@}

  //@{ \name Timing and flop count

  //! Returns the number of calls to Initialize().
  virtual int NumInitialize() const
  {
    return(NumInitialize_);
  }

  //! Returns the number of calls to Compute().
  virtual int NumCompute() const
  {
    return(NumCompute_);
  }

  //! Returns the number of calls to ApplyInverse().
  virtual int NumApplyInverse() const
  {
    return(NumApplyInverse_);
  }

  //! Returns the time spent in Initialize().
  virtual double InitializeTime() const
  {
    return(InitializeTime_);
  }

  //! Returns the time spent in Compute().
  virtual double ComputeTime() const
  {
    return(ComputeTime_);
  }

  //! Returns the time spent in ApplyInverse().
  virtual double ApplyInverseTime() const
  {
    return(ApplyInverseTime_);
  }

  //! Returns the number of flops in the initialization phase.
  virtual double InitializeFlops() const
  {
    return(0.0);
  }

  //! Returns the number of flops in the computation phase.
  virtual double ComputeFlops() const
  {
    return(ComputeFlops_);
  }

  //! Returns the number of flops for the application of the preconditioner.
  virtual double ApplyInverseFlops() const
  {
    return(ApplyInverseFlops_);
  }

  // @}
  // @{ \name Utility methods

  //! Simple power method to compute lambda_max.
  static int PowerMethod(const Epetra_Operator& Operator,
                         const Epetra_Vector& InvPointDiagonal,
                         const int MaximumIterations, 
                         double& LambdaMax);

  //! Uses AztecOO's CG to estimate lambda_min and lambda_max.
  static int CG(const Epetra_Operator& Operator, 
                const Epetra_Vector& InvPointDiagonal, 
                const int MaximumIterations, 
                double& lambda_min, double& lambda_max);

private:
  
  // @}
  // @{ \name Private methods
  
  //! Sets the label.
  virtual void SetLabel();

  //! Copy constructor (PRIVATE, should not be used)
  Ifpack_Chebyshev(const Ifpack_Chebyshev& rhs)
  {}
  
  //! operator = (PRIVATE, should not be used)
  Ifpack_Chebyshev& operator=(const Ifpack_Chebyshev& rhs)
  {
    return(*this);
  }

  // @{ Initializations, timing and flops
  //! If \c true, the preconditioner has been computed successfully.
  bool IsInitialized_;
  //! If \c true, the preconditioner has been computed successfully.
  bool IsComputed_;
  //! Contains the number of successful calls to Initialize().
  int NumInitialize_;
  //! Contains the number of successful call to Compute().
  int NumCompute_;
  //! Contains the number of successful call to ApplyInverse().
  mutable int NumApplyInverse_;
  //! Contains the time for all successful calls to Initialize().
  double InitializeTime_;
  //! Contains the time for all successful calls to Compute().
  double ComputeTime_;
  //! Contains the time for all successful calls to ApplyInverse().
  mutable double ApplyInverseTime_;
  //! Contains the number of flops for Compute().
  double ComputeFlops_;
  //! Contain sthe number of flops for ApplyInverse().
  mutable double ApplyInverseFlops_;
  // @}

  // @{ Settings
  //! Contains the degree of Chebyshev polynomial.
  int PolyDegree_;
  //! If true, use the tranpose of \c Matrix_.
  bool UseTranspose_;
  //! Contains the estimated condition number
  double Condest_;
  //! If true, Compute() also computes the condition number estimate.
  bool ComputeCondest_;
  //! Contains the ratio such that [LambdaMax_ / EigRatio_, LambdaMax_]
  //! is the interval of interest for the Chebyshev polynomial.
  double EigRatio_;
  //! Contains the label of this object.
  string Label_;
  //! Contains an approximation to the smallest eigenvalue.
  double LambdaMin_;
  //! Contains an approximation to the largest eigenvalue.
  double LambdaMax_;
  //! Contains the minimum value on the diagonal.
  double MinDiagonalValue_;
  // @}

  // @{ Other data
  //! Number of local rows.
  int NumMyRows_;
  //! Number of local nonzeros.
  int NumMyNonzeros_;
  //! Number of global rows.
  int NumGlobalRows_;
  //! Number of global nonzeros.
  int NumGlobalNonzeros_;
  //! Pointers to the matrix to be preconditioned as an Epetra_Operator.
  Teuchos::RefCountPtr<const Epetra_Operator> Operator_;
  //! Pointers to the matrix to be preconditioned as an Epetra_RowMatrix.
  Teuchos::RefCountPtr<const Epetra_RowMatrix> Matrix_;
  //! Contains the inverse of diagonal elements of \c Matrix.
  mutable Teuchos::RefCountPtr<Epetra_Vector> InvDiagonal_;
  //! If \c true, the Operator_ is an Epetra_RowMatrix.
  bool IsRowMatrix_;
  //! Time object to track timing.
  Teuchos::RefCountPtr<Epetra_Time> Time_;
  //! If \c true, the starting solution is always the zero vector.
  bool ZeroStartingSolution_;
  // @}

};


#endif // IFPACK_CHEBYSHEV_H