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+/*
+ * 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.optim.nonlinear.scalar;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.ArrayList;
+import java.util.Comparator;
+import org.apache.commons.math3.exception.NotStrictlyPositiveException;
+import org.apache.commons.math3.exception.NullArgumentException;
+import org.apache.commons.math3.random.RandomVectorGenerator;
+import org.apache.commons.math3.optim.BaseMultiStartMultivariateOptimizer;
+import org.apache.commons.math3.optim.PointValuePair;
+
+/**
+ * Multi-start optimizer.
+ *
+ * This class wraps an optimizer in order to use it several times in
+ * turn with different starting points (trying to avoid being trapped
+ * in a local extremum when looking for a global one).
+ *
+ * @since 3.0
+ */
+public class MultiStartMultivariateOptimizer
+ extends BaseMultiStartMultivariateOptimizer<PointValuePair> {
+ /** Underlying optimizer. */
+ private final MultivariateOptimizer optimizer;
+ /** Found optima. */
+ private final List<PointValuePair> optima = new ArrayList<PointValuePair>();
+
+ /**
+ * Create a multi-start optimizer from a single-start optimizer.
+ *
+ * @param optimizer Single-start optimizer to wrap.
+ * @param starts Number of starts to perform.
+ * If {@code starts == 1}, the result will be same as if {@code optimizer}
+ * is called directly.
+ * @param generator Random vector generator to use for restarts.
+ * @throws NullArgumentException if {@code optimizer} or {@code generator}
+ * is {@code null}.
+ * @throws NotStrictlyPositiveException if {@code starts < 1}.
+ */
+ public MultiStartMultivariateOptimizer(final MultivariateOptimizer optimizer,
+ final int starts,
+ final RandomVectorGenerator generator)
+ throws NullArgumentException,
+ NotStrictlyPositiveException {
+ super(optimizer, starts, generator);
+ this.optimizer = optimizer;
+ }
+
+ /**
+ * {@inheritDoc}
+ */
+ @Override
+ public PointValuePair[] getOptima() {
+ Collections.sort(optima, getPairComparator());
+ return optima.toArray(new PointValuePair[0]);
+ }
+
+ /**
+ * {@inheritDoc}
+ */
+ @Override
+ protected void store(PointValuePair optimum) {
+ optima.add(optimum);
+ }
+
+ /**
+ * {@inheritDoc}
+ */
+ @Override
+ protected void clear() {
+ optima.clear();
+ }
+
+ /**
+ * @return a comparator for sorting the optima.
+ */
+ private Comparator<PointValuePair> getPairComparator() {
+ return new Comparator<PointValuePair>() {
+ /** {@inheritDoc} */
+ public int compare(final PointValuePair o1,
+ final PointValuePair o2) {
+ if (o1 == null) {
+ return (o2 == null) ? 0 : 1;
+ } else if (o2 == null) {
+ return -1;
+ }
+ final double v1 = o1.getValue();
+ final double v2 = o2.getValue();
+ return (optimizer.getGoalType() == GoalType.MINIMIZE) ?
+ Double.compare(v1, v2) : Double.compare(v2, v1);
+ }
+ };
+ }
+}