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.math3.optimization.general;
019    
020    /**
021     * Available choices of update formulas for the β parameter
022     * in {@link NonLinearConjugateGradientOptimizer}.
023     * <p>
024     * The &beta; parameter is used to compute the successive conjugate
025     * search directions. For non-linear conjugate gradients, there are
026     * two formulas to compute &beta;:
027     * <ul>
028     *   <li>Fletcher-Reeves formula</li>
029     *   <li>Polak-Ribi&egrave;re formula</li>
030     * </ul>
031     * On the one hand, the Fletcher-Reeves formula is guaranteed to converge
032     * if the start point is close enough of the optimum whether the
033     * Polak-Ribi&egrave;re formula may not converge in rare cases. On the
034     * other hand, the Polak-Ribi&egrave;re formula is often faster when it
035     * does converge. Polak-Ribi&egrave;re is often used.
036     * <p>
037     * @see NonLinearConjugateGradientOptimizer
038     * @version $Id: ConjugateGradientFormula.java 1422230 2012-12-15 12:11:13Z erans $
039     * @deprecated As of 3.1 (to be removed in 4.0).
040     * @since 2.0
041     */
042    @Deprecated
043    public enum ConjugateGradientFormula {
044    
045        /** Fletcher-Reeves formula. */
046        FLETCHER_REEVES,
047    
048        /** Polak-Ribi&egrave;re formula. */
049        POLAK_RIBIERE
050    
051    }