001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    
018    package org.apache.commons.math.optimization;
019    
020    /** This interface specifies how to check if a {@link
021     * DifferentiableMultivariateVectorialOptimizer optimization algorithm} has converged.
022     *
023     * <p>Deciding if convergence has been reached is a problem-dependent issue. The
024     * user should provide a class implementing this interface to allow the optimization
025     * algorithm to stop its search according to the problem at hand.</p>
026     * <p>For convenience, two implementations that fit simple needs are already provided:
027     * {@link SimpleVectorialValueChecker} and {@link SimpleVectorialPointChecker}. The first
028     * one considers convergence is reached when the objective function value does not
029     * change much anymore, it does not use the point set at all. The second one
030     * considers convergence is reached when the input point set does not change
031     * much anymore, it does not use objective function value at all.</p>
032     *
033     * @version $Revision: 780674 $ $Date: 2009-06-01 17:10:55 +0200 (lun. 01 juin 2009) $
034     * @since 2.0
035     */
036    
037    public interface VectorialConvergenceChecker {
038    
039      /** Check if the optimization algorithm has converged considering the last points.
040       * <p>
041       * This method may be called several time from the same algorithm iteration with
042       * different points. This can be detected by checking the iteration number at each
043       * call if needed. Each time this method is called, the previous and current point
044       * correspond to points with the same role at each iteration, so they can be
045       * compared. As an example, simplex-based algorithms call this method for all
046       * points of the simplex, not only for the best or worst ones.
047       * </p>
048       * @param iteration index of current iteration
049       * @param previous point from previous iteration
050       * @param current point from current iteration
051       * @return true if the algorithm is considered to have converged
052       */
053      boolean converged(int iteration, VectorialPointValuePair previous, VectorialPointValuePair current);
054    
055    }