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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.util.IterationEvent;
import org.apache.commons.math3.exception.MathUnsupportedOperationException;

This is the base class for all events occurring during the iterations of a IterativeLinearSolver. 
Since:
3.0/**
 * 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. /** Serialization identifier. */
    private static final long serialVersionUID = 20120129L;

    
Creates a new instance of this class.
Params:
source – the iterative algorithm on which the event initially
occurred
iterations – the number of iterations performed at the time this event is created/**
     * 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 IterativeLinearSolver. 
Returns:
the right-hand side vector, b/**
     * 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 exact. Instead, the norm of the so-called updated residual (if available) should be returned. For example, the 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, Predicting the Behavior of Finite Precision Lanzos and
Conjugate Gradient Computations, Technical Report 538, Department of
Computer Science, New York University, 1991 (available
here).
Returns:
the norm of the residual, ||r||/**
     * 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


this method should throw a MathUnsupportedOperationException,
providesResidual() returns false.

 The default implementation throws a MathUnsupportedOperationException. If this method is overriden, then providesResidual() should be overriden as well. 
Returns:
the updated residual, r/**
     * <p>
     * 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
     * </p>
     * <ul>
     * <li>this method should throw a
     * {@link MathUnsupportedOperationException},</li>
     * <li>{@link #providesResidual()} returns {@code false}.</li>
     * </ul>
     * <p>
     * The default implementation throws a
     * {@link MathUnsupportedOperationException}. If this method is overriden,
     * then {@link #providesResidual()} should be overriden as well.
     * </p>
     *
     * @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 IterativeLinearSolver. 
Returns:
the solution, x/**
     * 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 true if getResidual() is supported. The default implementation returns false. 
Returns:
false if getResidual() throws a MathUnsupportedOperationException/**
     * 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;
    }
}