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Java example source code file (SimpleVectorValueChecker.java)

This example Java source code file (SimpleVectorValueChecker.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

abstractconvergencechecker, deprecated, iteration_check_disabled, notstrictlypositiveexception, override, pointvectorvaluepair, simplevectorvaluechecker

The SimpleVectorValueChecker.java Java example source code

/*
 * 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.optimization;

import org.apache.commons.math3.util.FastMath;
import org.apache.commons.math3.exception.NotStrictlyPositiveException;

/**
 * Simple implementation of the {@link ConvergenceChecker} interface using
 * only objective function values.
 *
 * Convergence is considered to have been reached if either the relative
 * difference between the objective function values is smaller than a
 * threshold or if either the absolute difference between the objective
 * function values is smaller than another threshold for all vectors elements.
 * <br/>
 * The {@link #converged(int,PointVectorValuePair,PointVectorValuePair) converged}
 * method will also return {@code true} if the number of iterations has been set
 * (see {@link #SimpleVectorValueChecker(double,double,int) this constructor}).
 *
 * @deprecated As of 3.1 (to be removed in 4.0).
 * @since 3.0
 */
@Deprecated
public class SimpleVectorValueChecker
    extends AbstractConvergenceChecker<PointVectorValuePair> {
    /**
     * If {@link #maxIterationCount} is set to this value, the number of
     * iterations will never cause
     * {@link #converged(int,PointVectorValuePair,PointVectorValuePair)}
     * to return {@code true}.
     */
    private static final int ITERATION_CHECK_DISABLED = -1;
    /**
     * Number of iterations after which the
     * {@link #converged(int,PointVectorValuePair,PointVectorValuePair)} method
     * will return true (unless the check is disabled).
     */
    private final int maxIterationCount;

    /**
     * Build an instance with default thresholds.
     * @deprecated See {@link AbstractConvergenceChecker#AbstractConvergenceChecker()}
     */
    @Deprecated
    public SimpleVectorValueChecker() {
        maxIterationCount = ITERATION_CHECK_DISABLED;
    }

    /**
     * Build an instance with specified thresholds.
     *
     * In order to perform only relative checks, the absolute tolerance
     * must be set to a negative value. In order to perform only absolute
     * checks, the relative tolerance must be set to a negative value.
     *
     * @param relativeThreshold relative tolerance threshold
     * @param absoluteThreshold absolute tolerance threshold
     */
    public SimpleVectorValueChecker(final double relativeThreshold,
                                    final double absoluteThreshold) {
        super(relativeThreshold, absoluteThreshold);
        maxIterationCount = ITERATION_CHECK_DISABLED;
    }

    /**
     * Builds an instance with specified tolerance thresholds and
     * iteration count.
     *
     * In order to perform only relative checks, the absolute tolerance
     * must be set to a negative value. In order to perform only absolute
     * checks, the relative tolerance must be set to a negative value.
     *
     * @param relativeThreshold Relative tolerance threshold.
     * @param absoluteThreshold Absolute tolerance threshold.
     * @param maxIter Maximum iteration count.
     * @throws NotStrictlyPositiveException if {@code maxIter <= 0}.
     *
     * @since 3.1
     */
    public SimpleVectorValueChecker(final double relativeThreshold,
                                    final double absoluteThreshold,
                                    final int maxIter) {
        super(relativeThreshold, absoluteThreshold);

        if (maxIter <= 0) {
            throw new NotStrictlyPositiveException(maxIter);
        }
        maxIterationCount = maxIter;
    }

    /**
     * Check if the optimization algorithm has converged considering the
     * last two points.
     * This method may be called several times from the same algorithm
     * iteration with different points. This can be detected by checking the
     * iteration number at each call if needed. Each time this method is
     * called, the previous and current point correspond to points with the
     * same role at each iteration, so they can be compared. As an example,
     * simplex-based algorithms call this method for all points of the simplex,
     * not only for the best or worst ones.
     *
     * @param iteration Index of current iteration
     * @param previous Best point in the previous iteration.
     * @param current Best point in the current iteration.
     * @return {@code true} if the arguments satify the convergence criterion.
     */
    @Override
    public boolean converged(final int iteration,
                             final PointVectorValuePair previous,
                             final PointVectorValuePair current) {
        if (maxIterationCount != ITERATION_CHECK_DISABLED && iteration >= maxIterationCount) {
            return true;
        }

        final double[] p = previous.getValueRef();
        final double[] c = current.getValueRef();
        for (int i = 0; i < p.length; ++i) {
            final double pi         = p[i];
            final double ci         = c[i];
            final double difference = FastMath.abs(pi - ci);
            final double size       = FastMath.max(FastMath.abs(pi), FastMath.abs(ci));
            if (difference > size * getRelativeThreshold() &&
                difference > getAbsoluteThreshold()) {
                return false;
            }
        }
        return true;
    }
}

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