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 */
017package org.apache.commons.math4.legacy.optim;
018
019import org.apache.commons.math4.legacy.exception.TooManyEvaluationsException;
020import org.apache.commons.math4.legacy.exception.TooManyIterationsException;
021import org.apache.commons.math4.legacy.core.IntegerSequence;
022
023/**
024 * Base class for implementing optimizers.
025 * It contains the boiler-plate code for counting the number of evaluations
026 * of the objective function and the number of iterations of the algorithm,
027 * and storing the convergence checker.
028 * <em>It is not a "user" class.</em>
029 *
030 * @param <PAIR> Type of the point/value pair returned by the optimization
031 * algorithm.
032 *
033 * @since 3.1
034 */
035public abstract class BaseOptimizer<PAIR> {
036    /** Callback to use for the evaluation counter. */
037    private static final MaxEvalCallback MAX_EVAL_CALLBACK = new MaxEvalCallback();
038    /** Callback to use for the iteration counter. */
039    private static final MaxIterCallback MAX_ITER_CALLBACK = new MaxIterCallback();
040
041    /** Convergence checker. */
042    private final ConvergenceChecker<PAIR> checker;
043    /** Maximum number of evaluations. */
044    private int maxEvaluations;
045    /** Maximum number of iterations. */
046    private int maxIterations;
047    /** Evaluations counter. */
048    private IntegerSequence.Incrementor evaluations;
049    /** Iterations counter. */
050    private IntegerSequence.Incrementor iterations;
051
052    /**
053     * @param checker Convergence checker.
054     */
055    protected BaseOptimizer(ConvergenceChecker<PAIR> checker) {
056        this(checker, 0, Integer.MAX_VALUE);
057    }
058
059    /**
060     * @param checker Convergence checker.
061     * @param maxEval Maximum number of objective function evaluations.
062     * @param maxIter Maximum number of algorithm iterations.
063     */
064    protected BaseOptimizer(ConvergenceChecker<PAIR> checker,
065                            int maxEval,
066                            int maxIter) {
067        this.checker = checker;
068        this.maxEvaluations = maxEval;
069        this.maxIterations = maxIter;
070    }
071
072    /**
073     * Gets the maximal number of function evaluations.
074     *
075     * @return the maximal number of function evaluations.
076     */
077    public int getMaxEvaluations() {
078        return evaluations.getMaximalCount();
079    }
080
081    /**
082     * Gets the number of evaluations of the objective function.
083     * The number of evaluations corresponds to the last call to the
084     * {@code optimize} method. It is 0 if the method has not been
085     * called yet.
086     *
087     * @return the number of evaluations of the objective function.
088     */
089    public int getEvaluations() {
090        return evaluations.getCount();
091    }
092
093    /**
094     * Gets the maximal number of iterations.
095     *
096     * @return the maximal number of iterations.
097     */
098    public int getMaxIterations() {
099        return iterations.getMaximalCount();
100    }
101
102    /**
103     * Gets the number of iterations performed by the algorithm.
104     * The number iterations corresponds to the last call to the
105     * {@code optimize} method. It is 0 if the method has not been
106     * called yet.
107     *
108     * @return the number of evaluations of the objective function.
109     */
110    public int getIterations() {
111        return iterations.getCount();
112    }
113
114    /**
115     * Gets the convergence checker.
116     *
117     * @return the object used to check for convergence.
118     */
119    public ConvergenceChecker<PAIR> getConvergenceChecker() {
120        return checker;
121    }
122
123    /**
124     * Stores data and performs the optimization.
125     * <p>
126     * The list of parameters is open-ended so that sub-classes can extend it
127     * with arguments specific to their concrete implementations.
128     * <p>
129     * When the method is called multiple times, instance data is overwritten
130     * only when actually present in the list of arguments: when not specified,
131     * data set in a previous call is retained (and thus is optional in
132     * subsequent calls).
133     * <p>
134     * Important note: Subclasses <em>must</em> override
135     * {@link #parseOptimizationData(OptimizationData[])} if they need to register
136     * their own options; but then, they <em>must</em> also call
137     * {@code super.parseOptimizationData(optData)} within that method.
138     *
139     * @param optData Optimization data.
140     * This method will register the following data:
141     * <ul>
142     *  <li>{@link MaxEval}</li>
143     *  <li>{@link MaxIter}</li>
144     * </ul>
145     * @return a point/value pair that satisfies the convergence criteria.
146     * @throws TooManyEvaluationsException if the maximal number of
147     * evaluations is exceeded.
148     * @throws TooManyIterationsException if the maximal number of
149     * iterations is exceeded.
150     */
151    public PAIR optimize(OptimizationData... optData) {
152        // Parse options.
153        parseOptimizationData(optData);
154        // Reset counters.
155        resetCounters();
156        // Perform optimization.
157        return doOptimize();
158    }
159
160    /**
161     * Performs the optimization.
162     *
163     * @return a point/value pair that satisfies the convergence criteria.
164     * @throws TooManyEvaluationsException if the maximal number of
165     * evaluations is exceeded.
166     * @throws TooManyIterationsException if the maximal number of
167     * iterations is exceeded.
168     */
169    public PAIR optimize() {
170        // Reset counters.
171        resetCounters();
172        // Perform optimization.
173        return doOptimize();
174    }
175
176    /**
177     * Performs the bulk of the optimization algorithm.
178     *
179     * @return the point/value pair giving the optimal value of the
180     * objective function.
181     */
182    protected abstract PAIR doOptimize();
183
184    /**
185     * Increment the evaluation count.
186     *
187     * @throws TooManyEvaluationsException if the allowed evaluations
188     * have been exhausted.
189     */
190    protected void incrementEvaluationCount() {
191        evaluations.increment();
192    }
193
194    /**
195     * Increment the iteration count.
196     *
197     * @throws TooManyIterationsException if the allowed iterations
198     * have been exhausted.
199     */
200    protected void incrementIterationCount() {
201        iterations.increment();
202    }
203
204    /**
205     * Scans the list of (required and optional) optimization data that
206     * characterize the problem.
207     *
208     * @param optData Optimization data.
209     * The following data will be looked for:
210     * <ul>
211     *  <li>{@link MaxEval}</li>
212     *  <li>{@link MaxIter}</li>
213     * </ul>
214     */
215    protected void parseOptimizationData(OptimizationData... optData) {
216        // The existing values (as set by the previous call) are reused if
217        // not provided in the argument list.
218        for (OptimizationData data : optData) {
219            if (data instanceof MaxEval) {
220                maxEvaluations = ((MaxEval) data).getMaxEval();
221                continue;
222            }
223            if (data instanceof MaxIter) {
224                maxIterations = ((MaxIter) data).getMaxIter();
225                continue;
226            }
227        }
228    }
229
230    /** Reset counters. */
231    private void resetCounters() {
232        evaluations = IntegerSequence.Incrementor.create()
233            .withMaximalCount(maxEvaluations)
234            .withCallback(MAX_EVAL_CALLBACK);
235        iterations = IntegerSequence.Incrementor.create()
236            .withMaximalCount(maxIterations)
237            .withCallback(MAX_ITER_CALLBACK);
238    }
239
240    /**
241     * Defines the action to perform when reaching the maximum number
242     * of evaluations.
243     */
244    private static class MaxEvalCallback
245        implements IntegerSequence.Incrementor.MaxCountExceededCallback {
246        /**
247         * {@inheritDoc}
248         * @throws TooManyEvaluationsException
249         */
250        @Override
251        public void trigger(int max) {
252            throw new TooManyEvaluationsException(max);
253        }
254    }
255
256    /**
257     * Defines the action to perform when reaching the maximum number
258     * of evaluations.
259     */
260    private static class MaxIterCallback
261        implements IntegerSequence.Incrementor.MaxCountExceededCallback {
262        /**
263         * {@inheritDoc}
264         * @throws TooManyIterationsException
265         */
266        @Override
267        public void trigger(int max) {
268            throw new TooManyIterationsException(max);
269        }
270    }
271}