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Java example source code file (DormandPrince54IntegratorTest.java)

This example Java source code file (DormandPrince54IntegratorTest.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

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Java - Java tags/keywords

dimensionmismatchexception, dormandprince54integrator, dp54smalllasthandler, firstorderintegrator, keplerhandler, maxcountexceededexception, nobracketingexception, numberistoosmallexception, stephandler, testproblem1, testproblem3, testproblem5, testproblemhandler, variablehandler

The DormandPrince54IntegratorTest.java Java example source code

/*
 * 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.ode.nonstiff;

import org.apache.commons.math3.exception.DimensionMismatchException;
import org.apache.commons.math3.exception.MaxCountExceededException;
import org.apache.commons.math3.exception.NoBracketingException;
import org.apache.commons.math3.exception.NumberIsTooSmallException;
import org.apache.commons.math3.ode.FirstOrderIntegrator;
import org.apache.commons.math3.ode.TestProblem1;
import org.apache.commons.math3.ode.TestProblem3;
import org.apache.commons.math3.ode.TestProblem4;
import org.apache.commons.math3.ode.TestProblem5;
import org.apache.commons.math3.ode.TestProblemAbstract;
import org.apache.commons.math3.ode.TestProblemHandler;
import org.apache.commons.math3.ode.events.EventHandler;
import org.apache.commons.math3.ode.sampling.StepHandler;
import org.apache.commons.math3.ode.sampling.StepInterpolator;
import org.apache.commons.math3.util.FastMath;
import org.junit.Assert;
import org.junit.Test;


public class DormandPrince54IntegratorTest {

  @Test(expected=DimensionMismatchException.class)
  public void testDimensionCheck()
      throws DimensionMismatchException, NumberIsTooSmallException,
             MaxCountExceededException, NoBracketingException {
      TestProblem1 pb = new TestProblem1();
      DormandPrince54Integrator integrator = new DormandPrince54Integrator(0.0, 1.0,
                                                                           1.0e-10, 1.0e-10);
      integrator.integrate(pb,
                           0.0, new double[pb.getDimension()+10],
                           1.0, new double[pb.getDimension()+10]);
  }

  @Test(expected=NumberIsTooSmallException.class)
  public void testMinStep()
      throws DimensionMismatchException, NumberIsTooSmallException,
             MaxCountExceededException, NoBracketingException {

      TestProblem1 pb = new TestProblem1();
      double minStep = 0.1 * (pb.getFinalTime() - pb.getInitialTime());
      double maxStep = pb.getFinalTime() - pb.getInitialTime();
      double[] vecAbsoluteTolerance = { 1.0e-15, 1.0e-16 };
      double[] vecRelativeTolerance = { 1.0e-15, 1.0e-16 };

      FirstOrderIntegrator integ = new DormandPrince54Integrator(minStep, maxStep,
                                                                 vecAbsoluteTolerance,
                                                                 vecRelativeTolerance);
      TestProblemHandler handler = new TestProblemHandler(pb, integ);
      integ.addStepHandler(handler);
      integ.integrate(pb,
                      pb.getInitialTime(), pb.getInitialState(),
                      pb.getFinalTime(), new double[pb.getDimension()]);
      Assert.fail("an exception should have been thrown");

  }

  @Test
  public void testSmallLastStep()
      throws DimensionMismatchException, NumberIsTooSmallException,
             MaxCountExceededException, NoBracketingException {

    TestProblemAbstract pb = new TestProblem5();
    double minStep = 1.25;
    double maxStep = FastMath.abs(pb.getFinalTime() - pb.getInitialTime());
    double scalAbsoluteTolerance = 6.0e-4;
    double scalRelativeTolerance = 6.0e-4;

    AdaptiveStepsizeIntegrator integ =
      new DormandPrince54Integrator(minStep, maxStep,
                                    scalAbsoluteTolerance,
                                    scalRelativeTolerance);

    DP54SmallLastHandler handler = new DP54SmallLastHandler(minStep);
    integ.addStepHandler(handler);
    integ.setInitialStepSize(1.7);
    integ.integrate(pb,
                    pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);
    Assert.assertTrue(handler.wasLastSeen());
    Assert.assertEquals("Dormand-Prince 5(4)", integ.getName());

  }

  @Test
  public void testBackward()
      throws DimensionMismatchException, NumberIsTooSmallException,
             MaxCountExceededException, NoBracketingException {

      TestProblem5 pb = new TestProblem5();
      double minStep = 0;
      double maxStep = pb.getFinalTime() - pb.getInitialTime();
      double scalAbsoluteTolerance = 1.0e-8;
      double scalRelativeTolerance = 0.01 * scalAbsoluteTolerance;

      FirstOrderIntegrator integ = new DormandPrince54Integrator(minStep, maxStep,
                                                                 scalAbsoluteTolerance,
                                                                 scalRelativeTolerance);
      TestProblemHandler handler = new TestProblemHandler(pb, integ);
      integ.addStepHandler(handler);
      integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(),
                      pb.getFinalTime(), new double[pb.getDimension()]);

      Assert.assertTrue(handler.getLastError() < 2.0e-7);
      Assert.assertTrue(handler.getMaximalValueError() < 2.0e-7);
      Assert.assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);
      Assert.assertEquals("Dormand-Prince 5(4)", integ.getName());
  }

  private static class DP54SmallLastHandler implements StepHandler {

    public DP54SmallLastHandler(double minStep) {
      lastSeen = false;
      this.minStep = minStep;
    }

    public void init(double t0, double[] y0, double t) {
    }

    public void handleStep(StepInterpolator interpolator, boolean isLast) {
      if (isLast) {
        lastSeen = true;
        double h = interpolator.getCurrentTime() - interpolator.getPreviousTime();
        Assert.assertTrue(FastMath.abs(h) < minStep);
      }
    }

    public boolean wasLastSeen() {
      return lastSeen;
    }

    private boolean lastSeen;
    private double  minStep;

  }

  @Test
  public void testIncreasingTolerance()
      throws DimensionMismatchException, NumberIsTooSmallException,
             MaxCountExceededException, NoBracketingException {

    int previousCalls = Integer.MAX_VALUE;
    for (int i = -12; i < -2; ++i) {
      TestProblem1 pb = new TestProblem1();
      double minStep = 0;
      double maxStep = pb.getFinalTime() - pb.getInitialTime();
      double scalAbsoluteTolerance = FastMath.pow(10.0, i);
      double scalRelativeTolerance = 0.01 * scalAbsoluteTolerance;

      EmbeddedRungeKuttaIntegrator integ =
          new DormandPrince54Integrator(minStep, maxStep,
                                        scalAbsoluteTolerance, scalRelativeTolerance);
      TestProblemHandler handler = new TestProblemHandler(pb, integ);
      integ.setSafety(0.8);
      integ.setMaxGrowth(5.0);
      integ.setMinReduction(0.3);
      integ.addStepHandler(handler);
      integ.integrate(pb,
                      pb.getInitialTime(), pb.getInitialState(),
                      pb.getFinalTime(), new double[pb.getDimension()]);
      Assert.assertEquals(0.8, integ.getSafety(), 1.0e-12);
      Assert.assertEquals(5.0, integ.getMaxGrowth(), 1.0e-12);
      Assert.assertEquals(0.3, integ.getMinReduction(), 1.0e-12);

      // the 0.7 factor is only valid for this test
      // and has been obtained from trial and error
      // there is no general relation between local and global errors
      Assert.assertTrue(handler.getMaximalValueError() < (0.7 * scalAbsoluteTolerance));
      Assert.assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);

      int calls = pb.getCalls();
      Assert.assertEquals(integ.getEvaluations(), calls);
      Assert.assertTrue(calls <= previousCalls);
      previousCalls = calls;

    }

  }

  @Test
  public void testEvents()
      throws DimensionMismatchException, NumberIsTooSmallException,
             MaxCountExceededException, NoBracketingException {

    TestProblem4 pb = new TestProblem4();
    double minStep = 0;
    double maxStep = pb.getFinalTime() - pb.getInitialTime();
    double scalAbsoluteTolerance = 1.0e-8;
    double scalRelativeTolerance = 0.01 * scalAbsoluteTolerance;

    FirstOrderIntegrator integ = new DormandPrince54Integrator(minStep, maxStep,
                                                               scalAbsoluteTolerance,
                                                               scalRelativeTolerance);
    TestProblemHandler handler = new TestProblemHandler(pb, integ);
    integ.addStepHandler(handler);
    EventHandler[] functions = pb.getEventsHandlers();
    double convergence = 1.0e-8 * maxStep;
    for (int l = 0; l < functions.length; ++l) {
      integ.addEventHandler(functions[l],
                                 Double.POSITIVE_INFINITY, convergence, 1000);
    }
    Assert.assertEquals(functions.length, integ.getEventHandlers().size());
    integ.integrate(pb,
                    pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);

    Assert.assertTrue(handler.getMaximalValueError() < 5.0e-6);
    Assert.assertEquals(0, handler.getMaximalTimeError(), convergence);
    Assert.assertEquals(12.0, handler.getLastTime(), convergence);
    integ.clearEventHandlers();
    Assert.assertEquals(0, integ.getEventHandlers().size());

  }

  @Test
  public void testKepler()
      throws DimensionMismatchException, NumberIsTooSmallException,
             MaxCountExceededException, NoBracketingException {

    final TestProblem3 pb  = new TestProblem3(0.9);
    double minStep = 0;
    double maxStep = pb.getFinalTime() - pb.getInitialTime();
    double scalAbsoluteTolerance = 1.0e-8;
    double scalRelativeTolerance = scalAbsoluteTolerance;

    FirstOrderIntegrator integ = new DormandPrince54Integrator(minStep, maxStep,
                                                               scalAbsoluteTolerance,
                                                               scalRelativeTolerance);
    integ.addStepHandler(new KeplerHandler(pb));
    integ.integrate(pb,
                    pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);

    Assert.assertEquals(integ.getEvaluations(), pb.getCalls());
    Assert.assertTrue(pb.getCalls() < 2800);

  }

  @Test
  public void testVariableSteps()
      throws DimensionMismatchException, NumberIsTooSmallException,
             MaxCountExceededException, NoBracketingException {

    final TestProblem3 pb  = new TestProblem3(0.9);
    double minStep = 0;
    double maxStep = pb.getFinalTime() - pb.getInitialTime();
    double scalAbsoluteTolerance = 1.0e-8;
    double scalRelativeTolerance = scalAbsoluteTolerance;

    FirstOrderIntegrator integ = new DormandPrince54Integrator(minStep, maxStep,
                                                               scalAbsoluteTolerance,
                                                               scalRelativeTolerance);
    integ.addStepHandler(new VariableHandler());
    double stopTime = integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(),
                                      pb.getFinalTime(), new double[pb.getDimension()]);
    Assert.assertEquals(pb.getFinalTime(), stopTime, 1.0e-10);
  }

  private static class KeplerHandler implements StepHandler {
    public KeplerHandler(TestProblem3 pb) {
      this.pb = pb;
    }
    public void init(double t0, double[] y0, double t) {
      nbSteps = 0;
      maxError = 0;
    }
    public void handleStep(StepInterpolator interpolator, boolean isLast)
        throws MaxCountExceededException {

      ++nbSteps;
      for (int a = 1; a < 10; ++a) {

        double prev   = interpolator.getPreviousTime();
        double curr   = interpolator.getCurrentTime();
        double interp = ((10 - a) * prev + a * curr) / 10;
        interpolator.setInterpolatedTime(interp);

        double[] interpolatedY = interpolator.getInterpolatedState ();
        double[] theoreticalY  = pb.computeTheoreticalState(interpolator.getInterpolatedTime());
        double dx = interpolatedY[0] - theoreticalY[0];
        double dy = interpolatedY[1] - theoreticalY[1];
        double error = dx * dx + dy * dy;
        if (error > maxError) {
          maxError = error;
        }
      }
      if (isLast) {
        Assert.assertTrue(maxError < 7.0e-10);
        Assert.assertTrue(nbSteps < 400);
      }
    }
    private int nbSteps;
    private double maxError;
    private TestProblem3 pb;
  }

  private static class VariableHandler implements StepHandler {
    public VariableHandler() {
      firstTime = true;
      minStep = 0;
      maxStep = 0;
    }
    public void init(double t0, double[] y0, double t) {
      firstTime = true;
      minStep = 0;
      maxStep = 0;
    }
    public void handleStep(StepInterpolator interpolator,
                           boolean isLast) {

      double step = FastMath.abs(interpolator.getCurrentTime()
                             - interpolator.getPreviousTime());
      if (firstTime) {
        minStep   = FastMath.abs(step);
        maxStep   = minStep;
        firstTime = false;
      } else {
        if (step < minStep) {
          minStep = step;
        }
        if (step > maxStep) {
          maxStep = step;
        }
      }

      if (isLast) {
        Assert.assertTrue(minStep < (1.0 / 450.0));
        Assert.assertTrue(maxStep > (1.0 / 4.2));
      }
    }
    private boolean firstTime;
    private double  minStep;
    private double  maxStep;
  }

}

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