/*
 * 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;

/**
 * This interface specifies how to check if an optimization algorithm has converged. <br>
 * Deciding if convergence has been reached is a problem-dependent issue. The user should provide a
 * class implementing this interface to allow the optimization algorithm to stop its search
 * according to the problem at hand. <br>
 * For convenience, three implementations that fit simple needs are already provided: {@link
 * SimpleValueChecker}, {@link SimpleVectorValueChecker} and {@link SimplePointChecker}. The first
 * two consider that convergence is reached when the objective function value does not change much
 * anymore, it does not use the point set at all. The third one considers that convergence is
 * reached when the input point set does not change much anymore, it does not use objective function
 * value at all.
 *
 * @param <PAIR> Type of the (point, objective value) pair.
 * @see org.apache.commons.math3.optimization.SimplePointChecker
 * @see org.apache.commons.math3.optimization.SimpleValueChecker
 * @see org.apache.commons.math3.optimization.SimpleVectorValueChecker
 * @deprecated As of 3.1 (to be removed in 4.0).
 * @since 3.0
 */
@Deprecated
public interface ConvergenceChecker<PAIR> {
    /**
     * Check if the optimization algorithm has converged.
     *
     * @param iteration Current iteration.
     * @param previous Best point in the previous iteration.
     * @param current Best point in the current iteration.
     * @return {@code true} if the algorithm is considered to have converged.
     */
    boolean converged(int iteration, PAIR previous, PAIR current);
}