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 DormandPrince853StepInterpolatorTest {
040    
041      @Test
042      public void derivativesConsistency()
043      throws DerivativeException, IntegratorException {
044        TestProblem3 pb = new TestProblem3(0.1);
045        double minStep = 0;
046        double maxStep = pb.getFinalTime() - pb.getInitialTime();
047        double scalAbsoluteTolerance = 1.0e-8;
048        double scalRelativeTolerance = scalAbsoluteTolerance;
049        DormandPrince853Integrator integ = new DormandPrince853Integrator(minStep, maxStep,
050                                                                          scalAbsoluteTolerance,
051                                                                          scalRelativeTolerance);
052        StepInterpolatorTestUtils.checkDerivativesConsistency(integ, pb, 1.0e-10);
053      }
054    
055      @Test
056      public void serialization()
057        throws DerivativeException, IntegratorException,
058               IOException, ClassNotFoundException {
059    
060        TestProblem3 pb = new TestProblem3(0.9);
061        double minStep = 0;
062        double maxStep = pb.getFinalTime() - pb.getInitialTime();
063        double scalAbsoluteTolerance = 1.0e-8;
064        double scalRelativeTolerance = scalAbsoluteTolerance;
065        DormandPrince853Integrator integ = new DormandPrince853Integrator(minStep, maxStep,
066                                                                          scalAbsoluteTolerance,
067                                                                          scalRelativeTolerance);
068        integ.addStepHandler(new ContinuousOutputModel());
069        integ.integrate(pb,
070                        pb.getInitialTime(), pb.getInitialState(),
071                        pb.getFinalTime(), new double[pb.getDimension()]);
072    
073        ByteArrayOutputStream bos = new ByteArrayOutputStream();
074        ObjectOutputStream    oos = new ObjectOutputStream(bos);
075        for (StepHandler handler : integ.getStepHandlers()) {
076            oos.writeObject(handler);
077        }
078    
079        assertTrue(bos.size () > 86000);
080        assertTrue(bos.size () < 87000);
081    
082        ByteArrayInputStream  bis = new ByteArrayInputStream(bos.toByteArray());
083        ObjectInputStream     ois = new ObjectInputStream(bis);
084        ContinuousOutputModel cm  = (ContinuousOutputModel) ois.readObject();
085    
086        Random random = new Random(347588535632l);
087        double maxError = 0.0;
088        for (int i = 0; i < 1000; ++i) {
089          double r = random.nextDouble();
090          double time = r * pb.getInitialTime() + (1.0 - r) * pb.getFinalTime();
091          cm.setInterpolatedTime(time);
092          double[] interpolatedY = cm.getInterpolatedState ();
093          double[] theoreticalY  = pb.computeTheoreticalState(time);
094          double dx = interpolatedY[0] - theoreticalY[0];
095          double dy = interpolatedY[1] - theoreticalY[1];
096          double error = dx * dx + dy * dy;
097          if (error > maxError) {
098            maxError = error;
099          }
100        }
101    
102        assertTrue(maxError < 2.4e-10);
103    
104      }
105    
106      @Test
107      public void checklone()
108      throws DerivativeException, IntegratorException {
109        TestProblem3 pb = new TestProblem3(0.9);
110        double minStep = 0;
111        double maxStep = pb.getFinalTime() - pb.getInitialTime();
112        double scalAbsoluteTolerance = 1.0e-8;
113        double scalRelativeTolerance = scalAbsoluteTolerance;
114        DormandPrince853Integrator integ = new DormandPrince853Integrator(minStep, maxStep,
115                                                                          scalAbsoluteTolerance,
116                                                                          scalRelativeTolerance);
117        integ.addStepHandler(new StepHandler() {
118            public void handleStep(StepInterpolator interpolator, boolean isLast)
119            throws DerivativeException {
120                StepInterpolator cloned = interpolator.copy();
121                double tA = cloned.getPreviousTime();
122                double tB = cloned.getCurrentTime();
123                double halfStep = Math.abs(tB - tA) / 2;
124                assertEquals(interpolator.getPreviousTime(), tA, 1.0e-12);
125                assertEquals(interpolator.getCurrentTime(), tB, 1.0e-12);
126                for (int i = 0; i < 10; ++i) {
127                    double t = (i * tB + (9 - i) * tA) / 9;
128                    interpolator.setInterpolatedTime(t);
129                    assertTrue(Math.abs(cloned.getInterpolatedTime() - t) > (halfStep / 10));
130                    cloned.setInterpolatedTime(t);
131                    assertEquals(t, cloned.getInterpolatedTime(), 1.0e-12);
132                    double[] referenceState = interpolator.getInterpolatedState();
133                    double[] cloneState     = cloned.getInterpolatedState();
134                    for (int j = 0; j < referenceState.length; ++j) {
135                        assertEquals(referenceState[j], cloneState[j], 1.0e-12);
136                    }
137                }
138            }
139            public boolean requiresDenseOutput() {
140                return true;
141            }
142            public void reset() {
143            }
144        });
145        integ.integrate(pb,
146                pb.getInitialTime(), pb.getInitialState(),
147                pb.getFinalTime(), new double[pb.getDimension()]);
148    
149      }
150    
151    }