Package org.apache.commons.math4.legacy.linear

Class RealLinearOperator

java.lang.Object

org.apache.commons.math4.legacy.linear.RealLinearOperator

Direct Known Subclasses:

AbstractRealMatrix, JacobiPreconditioner

public abstract class RealLinearOperator
extends Object

This class defines a linear operator operating on real (double) vector spaces. No direct access to the coefficients of the underlying matrix is provided. The motivation for such an interface is well stated by Barrett et al. (1994):

We restrict ourselves to iterative methods, which work by repeatedly improving an approximate solution until it is accurate enough. These methods access the coefficient matrix A of the linear system only via the matrix-vector product y = A · x (and perhaps z = A^T · x). Thus the user need only supply a subroutine for computing y (and perhaps z) given x, which permits full exploitation of the sparsity or other special structure of A.

Barret et al. (1994)

R. Barrett, M. Berry, T. F. Chan, J. Demmel, J. M. Donato, J. Dongarra, V. Eijkhout, R. Pozo, C. Romine and H. Van der Vorst, Templates for the Solution of Linear Systems: Building Blocks for Iterative Methods, SIAM

Since:

3.0

Constructor Summary

Constructors

Constructor	Description
RealLinearOperator()

Method Summary

Modifier and Type	Method	Description
abstract int	getColumnDimension()	Returns the dimension of the domain of this operator.
abstract int	getRowDimension()	Returns the dimension of the codomain of this operator.
boolean	isTransposable()	Returns true if this operator supports operateTranspose(RealVector).
abstract RealVector	operate(RealVector x)	Returns the result of multiplying this by the vector x.
RealVector	operateTranspose(RealVector x)	Returns the result of multiplying the transpose of this operator by the vector x (optional operation).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RealLinearOperator

public RealLinearOperator()

Method Detail

getRowDimension

public abstract int getRowDimension()

Returns the dimension of the codomain of this operator.

Returns:

the number of rows of the underlying matrix

getColumnDimension

public abstract int getColumnDimension()

Returns the dimension of the domain of this operator.

Returns:

the number of columns of the underlying matrix

operate

public abstract RealVector operate(RealVector x)
                            throws DimensionMismatchException

Returns the result of multiplying this by the vector x.

Parameters:

x - the vector to operate on

Returns:

the product of this instance with x

Throws:

DimensionMismatchException - if the column dimension does not match the size of x

operateTranspose

public RealVector operateTranspose(RealVector x)
                            throws DimensionMismatchException,
                                   UnsupportedOperationException

Returns the result of multiplying the transpose of this operator by the vector x (optional operation). The default implementation throws an UnsupportedOperationException. Users overriding this method must also override isTransposable().

Parameters:

x - the vector to operate on

Returns:

the product of the transpose of this instance with x

Throws:

DimensionMismatchException - if the row dimension does not match the size of x

UnsupportedOperationException - if this operation is not supported by this operator

isTransposable

public boolean isTransposable()

Returns true if this operator supports operateTranspose(RealVector). If true is returned, operateTranspose(RealVector) should not throw UnsupportedOperationException. The default implementation returns false.

Returns:

false