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Ifpack_ILUT Class Reference

Ifpack_ILUT: A class for constructing and using an incomplete LU factorization of a given Epetra_RowMatrix. More...

#include <Ifpack_ILUT.h>

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## Public Member Functions

Ifpack_ILUT (const Epetra_RowMatrix *A)
Ifpack_ILUT constuctor with variable number of indices per row.

virtual ~Ifpack_ILUT ()
Ifpack_ILUT Destructor.

int SetParameters (Teuchos::ParameterList &parameterlis)
Set parameters using a Teuchos::ParameterList object.

int Initialize ()
Initialize L and U with values from user matrix A. More...

bool IsInitialized () const
Returns true if the preconditioner has been successfully initialized.

int Compute ()
Compute IC factor U using the specified graph, diagonal perturbation thresholds and relaxation parameters. More...

bool IsComputed () const
If factor is completed, this query returns true, otherwise it returns false.

int ApplyInverse (const Epetra_MultiVector &X, Epetra_MultiVector &Y) const
Returns the result of a Ifpack_ILUT forward/back solve on a Epetra_MultiVector X in Y. More...

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

double Condest (const Ifpack_CondestType CT=Ifpack_Cheap, const int MaxIters=1550, const double Tol=1e-9, Epetra_RowMatrix *Matrix_in=0)
Computed the estimated condition number and returns the value.

double Condest () const
Returns the computed estimated condition number, or -1.0 if no computed.

int SetUseTranspose (bool UseTranspose_in)
If set true, transpose of this operator will be applied. More...

double NormInf () const
Returns 0.0 because this class cannot compute Inf-norm.

bool HasNormInf () const
Returns false because this class cannot compute an Inf-norm.

bool UseTranspose () const
Returns the current UseTranspose setting.

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

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

const Epetra_Comm & Comm () const
Returns the Epetra_BlockMap object associated with the range of this matrix operator.

const Epetra_RowMatrix & Matrix () const
Returns a reference to the matrix to be preconditioned.

const Epetra_CrsMatrix & L () const
Returns a reference to the L factor.

const Epetra_CrsMatrix & U () const
Returns a reference to the U factor.

const char * Label () const
Returns the label of this object.

int SetLabel (const char *Label_in)
Sets the label for this object.

virtual ostream & Print (std::ostream &os) const
Prints basic information on iostream. This function is used by operator<<.

virtual int NumInitialize () const
Returns the number of calls to Initialize().

virtual int NumCompute () const
Returns the number of calls to Compute().

virtual int NumApplyInverse () const
Returns the number of calls to ApplyInverse().

virtual double InitializeTime () const
Returns the time spent in Initialize().

virtual double ComputeTime () const
Returns the time spent in Compute().

virtual double ApplyInverseTime () const
Returns the time spent in ApplyInverse().

virtual double InitializeFlops () const
Returns the number of flops in the initialization phase.

virtual double ComputeFlops () const
Returns the number of flops in the computation phase.

virtual double ApplyInverseFlops () const
Returns the number of flops in the application of the preconditioner.

double LevelOfFill () const

double RelaxValue () const
Set relative threshold value.

double AbsoluteThreshold () const
Get absolute threshold value.

double RelativeThreshold () const
Get relative threshold value.

double DropTolerance () const
Gets the dropping tolerance.

int NumGlobalNonzeros () const
Returns the number of nonzero entries in the global graph.

long long NumGlobalNonzeros64 () const

int NumMyNonzeros () const
Returns the number of nonzero entries in the local graph.

## Detailed Description

Ifpack_ILUT: A class for constructing and using an incomplete LU factorization of a given Epetra_RowMatrix.

The Ifpack_ILUT class computes a "Relaxed" ILUT factorization with dual threshold dropping of small elements of a given Epetra_RowMatrix.

This implementation does not use the algorithm that is described in General description of incomplete factorizations. The algorithm drops entries in a row (i) of matrix A that are smaller than drop_tolerance even before the factorization of row i then computes the factorization for that row. This is different than the usual algorithm where the drop tolerance is applied to the factored rows.

The complete list of supported parameters is reported in page List of Supported Parameters.

Date

Definition at line 81 of file Ifpack_ILUT.h.

## Member Function Documentation

 int Ifpack_ILUT::ApplyInverse ( const Epetra_MultiVector & X, Epetra_MultiVector & Y ) const
virtual

Returns the result of a Ifpack_ILUT forward/back solve on a Epetra_MultiVector X in Y.

Parameters
 X - (In) A Epetra_MultiVector of dimension NumVectors to solve for. Y - (Out) A Epetra_MultiVector of dimension NumVectorscontaining result.
Returns
Integer error code, set to 0 if successful.

Implements Ifpack_Preconditioner.

Definition at line 534 of file Ifpack_ILUT.cpp.

References IsComputed().

 int Ifpack_ILUT::Compute ( )
virtual

Compute IC factor U using the specified graph, diagonal perturbation thresholds and relaxation parameters.

This function computes the RILU(k) factors L and U using the current:

1. Ifpack_IlukGraph specifying the structure of L and U.
2. Value for the RILU(k) relaxation parameter.
3. Value for the a priori diagonal threshold values.

InitValues() must be called before the factorization can proceed.

Implements Ifpack_Preconditioner.

Definition at line 492 of file Ifpack_ILUT.cpp.

References Comm(), Initialize(), and IsInitialized().

 int Ifpack_ILUT::Initialize ( )
virtual

Initialize L and U with values from user matrix A.

Copies values from the user's matrix into the nonzero pattern of L and U.

Parameters
 In A - User matrix to be factored.
Warning
The graph of A must be identical to the graph passed in to Ifpack_IlukGraph constructor.

Implements Ifpack_Preconditioner.

Definition at line 141 of file Ifpack_ILUT.cpp.

References Comm(), and Matrix().

Referenced by Compute().

 int Ifpack_ILUT::SetUseTranspose ( bool UseTranspose_in )
inline

If set true, transpose of this operator will be applied.

This flag allows the transpose of the given operator to be used implicitly. Setting this flag affects only the Apply() and ApplyInverse() methods. If the implementation of this interface does not support transpose use, this method should return a value of -1.

Parameters
 UseTranspose_in - (In) If true, multiply by the transpose of operator, otherwise just use operator.
Returns
Always returns 0.

Definition at line 169 of file Ifpack_ILUT.h.

The documentation for this class was generated from the following files: