    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 an {@link MultivariateRealOptimizer optimization
    021     * 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 SimpleScalarValueChecker} and {@link SimpleRealPointChecker}. 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: 799857 $ $Date: 2009-08-01 15:07:12 +0200 (sam. 01 ao??t 2009) $
    034     * @since 2.0
    035     */
    036
    037    public interface RealConvergenceChecker {
    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, RealPointValuePair previous, RealPointValuePair current);
    054
    055    }