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Diffstat (limited to 'src/main/java/org/apache/commons/math3/optimization/SimplePointChecker.java')
| -rw-r--r-- | src/main/java/org/apache/commons/math3/optimization/SimplePointChecker.java | 130 |
1 files changed, 130 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/math3/optimization/SimplePointChecker.java b/src/main/java/org/apache/commons/math3/optimization/SimplePointChecker.java new file mode 100644 index 0000000..50ee2c5 --- /dev/null +++ b/src/main/java/org/apache/commons/math3/optimization/SimplePointChecker.java @@ -0,0 +1,130 @@ +/* + * 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.exception.NotStrictlyPositiveException; +import org.apache.commons.math3.util.FastMath; +import org.apache.commons.math3.util.Pair; + +/** + * Simple implementation of the {@link ConvergenceChecker} interface using only point coordinates. + * + * <p>Convergence is considered to have been reached if either the relative difference between each + * point coordinate are smaller than a threshold or if either the absolute difference between the + * point coordinates are smaller than another threshold. <br> + * The {@link #converged(int,Pair,Pair) converged} method will also return {@code true} if the + * number of iterations has been set (see {@link #SimplePointChecker(double,double,int) this + * constructor}). + * + * @param <PAIR> Type of the (point, value) pair. The type of the "value" part of the pair (not used + * by this class). + * @deprecated As of 3.1 (to be removed in 4.0). + * @since 3.0 + */ +@Deprecated +public class SimplePointChecker<PAIR extends Pair<double[], ? extends Object>> + extends AbstractConvergenceChecker<PAIR> { + /** + * If {@link #maxIterationCount} is set to this value, the number of iterations will never cause + * {@link #converged(int, Pair, Pair)} to return {@code true}. + */ + private static final int ITERATION_CHECK_DISABLED = -1; + + /** + * Number of iterations after which the {@link #converged(int, Pair, Pair)} method will return + * true (unless the check is disabled). + */ + private final int maxIterationCount; + + /** + * Build an instance with default threshold. + * + * @deprecated See {@link AbstractConvergenceChecker#AbstractConvergenceChecker()} + */ + @Deprecated + public SimplePointChecker() { + 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 SimplePointChecker(final double relativeThreshold, final double absoluteThreshold) { + super(relativeThreshold, absoluteThreshold); + maxIterationCount = ITERATION_CHECK_DISABLED; + } + + /** + * Builds 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. + * @param maxIter Maximum iteration count. + * @throws NotStrictlyPositiveException if {@code maxIter <= 0}. + * @since 3.1 + */ + public SimplePointChecker( + 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 PAIR previous, final PAIR current) { + if (maxIterationCount != ITERATION_CHECK_DISABLED && iteration >= maxIterationCount) { + return true; + } + + final double[] p = previous.getKey(); + final double[] c = current.getKey(); + 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; + } +} |