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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.math3.linear;
import org.apache.commons.math3.exception.MathUnsupportedOperationException;
import org.apache.commons.math3.util.IterationEvent;
/**
* This is the base class for all events occurring during the iterations of a {@link
* IterativeLinearSolver}.
*
* @since 3.0
*/
public abstract class IterativeLinearSolverEvent extends IterationEvent {
/** Serialization identifier. */
private static final long serialVersionUID = 20120129L;
/**
* Creates a new instance of this class.
*
* @param source the iterative algorithm on which the event initially occurred
* @param iterations the number of iterations performed at the time {@code this} event is
* created
*/
public IterativeLinearSolverEvent(final Object source, final int iterations) {
super(source, iterations);
}
/**
* Returns the current right-hand side of the linear system to be solved. This method should
* return an unmodifiable view, or a deep copy of the actual right-hand side vector, in order
* not to compromise subsequent iterations of the source {@link IterativeLinearSolver}.
*
* @return the right-hand side vector, b
*/
public abstract RealVector getRightHandSideVector();
/**
* Returns the norm of the residual. The returned value is not required to be <em>exact</em>.
* Instead, the norm of the so-called <em>updated</em> residual (if available) should be
* returned. For example, the {@link ConjugateGradient conjugate gradient} method computes a
* sequence of residuals, the norm of which is cheap to compute. However, due to accumulation of
* round-off errors, this residual might differ from the true residual after some iterations.
* See e.g. A. Greenbaum and Z. Strakos, <em>Predicting the Behavior of Finite Precision Lanzos
* and Conjugate Gradient Computations</em>, Technical Report 538, Department of Computer
* Science, New York University, 1991 (available <a
* href="http://www.archive.org/details/predictingbehavi00gree">here</a>).
*
* @return the norm of the residual, ||r||
*/
public abstract double getNormOfResidual();
/**
* Returns the residual. This is an optional operation, as all iterative linear solvers do not
* provide cheap estimate of the updated residual vector, in which case
*
* <ul>
* <li>this method should throw a {@link MathUnsupportedOperationException},
* <li>{@link #providesResidual()} returns {@code false}.
* </ul>
*
* <p>The default implementation throws a {@link MathUnsupportedOperationException}. If this
* method is overriden, then {@link #providesResidual()} should be overriden as well.
*
* @return the updated residual, r
*/
public RealVector getResidual() {
throw new MathUnsupportedOperationException();
}
/**
* Returns the current estimate of the solution to the linear system to be solved. This method
* should return an unmodifiable view, or a deep copy of the actual current solution, in order
* not to compromise subsequent iterations of the source {@link IterativeLinearSolver}.
*
* @return the solution, x
*/
public abstract RealVector getSolution();
/**
* Returns {@code true} if {@link #getResidual()} is supported. The default implementation
* returns {@code false}.
*
* @return {@code false} if {@link #getResidual()} throws a {@link
* MathUnsupportedOperationException}
*/
public boolean providesResidual() {
return false;
}
}
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