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.ode.nonstiff;
019    
020    import static org.junit.Assert.assertEquals;
021    import static org.junit.Assert.assertTrue;
022    
023    import java.io.ByteArrayInputStream;
024    import java.io.ByteArrayOutputStream;
025    import java.io.IOException;
026    import java.io.ObjectInputStream;
027    import java.io.ObjectOutputStream;
028    import java.util.Random;
029    
030    import org.apache.commons.math.ode.ContinuousOutputModel;
031    import org.apache.commons.math.ode.DerivativeException;
032    import org.apache.commons.math.ode.IntegratorException;
033    import org.apache.commons.math.ode.TestProblem3;
034    import org.apache.commons.math.ode.sampling.StepHandler;
035    import org.apache.commons.math.ode.sampling.StepInterpolator;
036    import org.apache.commons.math.ode.sampling.StepInterpolatorTestUtils;
037    import org.junit.Test;
038    
039    public class GraggBulirschStoerStepInterpolatorTest {
040    
041      @Test
042      public void derivativesConsistency()
043      throws DerivativeException, IntegratorException {
044        TestProblem3 pb = new TestProblem3(0.9);
045        double minStep   = 0;
046        double maxStep   = pb.getFinalTime() - pb.getInitialTime();
047        double absTolerance = 1.0e-8;
048        double relTolerance = 1.0e-8;
049    
050        GraggBulirschStoerIntegrator integ =
051          new GraggBulirschStoerIntegrator(minStep, maxStep,
052                                           absTolerance, relTolerance);
053        StepInterpolatorTestUtils.checkDerivativesConsistency(integ, pb, 1.0e-8);
054      }
055    
056      @Test
057      public void serialization()
058        throws DerivativeException, IntegratorException,
059               IOException, ClassNotFoundException {
060    
061        TestProblem3 pb  = new TestProblem3(0.9);
062        double minStep   = 0;
063        double maxStep   = pb.getFinalTime() - pb.getInitialTime();
064        double absTolerance = 1.0e-8;
065        double relTolerance = 1.0e-8;
066    
067        GraggBulirschStoerIntegrator integ =
068          new GraggBulirschStoerIntegrator(minStep, maxStep,
069                                           absTolerance, relTolerance);
070        integ.addStepHandler(new ContinuousOutputModel());
071        integ.integrate(pb,
072                        pb.getInitialTime(), pb.getInitialState(),
073                        pb.getFinalTime(), new double[pb.getDimension()]);
074    
075        ByteArrayOutputStream bos = new ByteArrayOutputStream();
076        ObjectOutputStream    oos = new ObjectOutputStream(bos);
077        for (StepHandler handler : integ.getStepHandlers()) {
078            oos.writeObject(handler);
079        }
080    
081        assertTrue(bos.size () > 34000);
082        assertTrue(bos.size () < 35000);
083    
084        ByteArrayInputStream  bis = new ByteArrayInputStream(bos.toByteArray());
085        ObjectInputStream     ois = new ObjectInputStream(bis);
086        ContinuousOutputModel cm  = (ContinuousOutputModel) ois.readObject();
087    
088        Random random = new Random(347588535632l);
089        double maxError = 0.0;
090        for (int i = 0; i < 1000; ++i) {
091          double r = random.nextDouble();
092          double time = r * pb.getInitialTime() + (1.0 - r) * pb.getFinalTime();
093          cm.setInterpolatedTime(time);
094          double[] interpolatedY = cm.getInterpolatedState ();
095          double[] theoreticalY  = pb.computeTheoreticalState(time);
096          double dx = interpolatedY[0] - theoreticalY[0];
097          double dy = interpolatedY[1] - theoreticalY[1];
098          double error = dx * dx + dy * dy;
099          if (error > maxError) {
100            maxError = error;
101          }
102        }
103    
104        assertTrue(maxError < 5.0e-11);
105    
106      }
107    
108      @Test
109      public void checklone()
110      throws DerivativeException, IntegratorException {
111        TestProblem3 pb = new TestProblem3(0.9);
112        double minStep = 0;
113        double maxStep = pb.getFinalTime() - pb.getInitialTime();
114        double scalAbsoluteTolerance = 1.0e-8;
115        double scalRelativeTolerance = scalAbsoluteTolerance;
116        GraggBulirschStoerIntegrator integ = new GraggBulirschStoerIntegrator(minStep, maxStep,
117                                                                              scalAbsoluteTolerance,
118                                                                              scalRelativeTolerance);
119        integ.addStepHandler(new StepHandler() {
120            public void handleStep(StepInterpolator interpolator, boolean isLast)
121            throws DerivativeException {
122                StepInterpolator cloned = interpolator.copy();
123                double tA = cloned.getPreviousTime();
124                double tB = cloned.getCurrentTime();
125                double halfStep = Math.abs(tB - tA) / 2;
126                assertEquals(interpolator.getPreviousTime(), tA, 1.0e-12);
127                assertEquals(interpolator.getCurrentTime(), tB, 1.0e-12);
128                for (int i = 0; i < 10; ++i) {
129                    double t = (i * tB + (9 - i) * tA) / 9;
130                    interpolator.setInterpolatedTime(t);
131                    assertTrue(Math.abs(cloned.getInterpolatedTime() - t) > (halfStep / 10));
132                    cloned.setInterpolatedTime(t);
133                    assertEquals(t, cloned.getInterpolatedTime(), 1.0e-12);
134                    double[] referenceState = interpolator.getInterpolatedState();
135                    double[] cloneState     = cloned.getInterpolatedState();
136                    for (int j = 0; j < referenceState.length; ++j) {
137                        assertEquals(referenceState[j], cloneState[j], 1.0e-12);
138                    }
139                }
140            }
141            public boolean requiresDenseOutput() {
142                return true;
143            }
144            public void reset() {
145            }
146        });
147        integ.integrate(pb,
148                pb.getInitialTime(), pb.getInitialState(),
149                pb.getFinalTime(), new double[pb.getDimension()]);
150    
151      }
152    
153    }