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Java example source code file (ContinuousOutputModelTest.java)

This example Java source code file (ContinuousOutputModelTest.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.

Learn more about this Java project at its project page.

Java - Java tags/keywords

after, continuousoutputmodel, continuousoutputmodeltest, dimensionmismatchexception, dormandprince853integrator, dummystepinterpolator, firstorderdifferentialequations, firstorderintegrator, mathillegalargumentexception, maxcountexceededexception, nobracketingexception, numberistoosmallexception, random, test, util

The ContinuousOutputModelTest.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;

import java.util.Random;

import org.apache.commons.math3.exception.DimensionMismatchException;
import org.apache.commons.math3.exception.MathIllegalArgumentException;
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.nonstiff.DormandPrince54Integrator;
import org.apache.commons.math3.ode.nonstiff.DormandPrince853Integrator;
import org.apache.commons.math3.ode.sampling.DummyStepInterpolator;
import org.apache.commons.math3.ode.sampling.StepInterpolator;
import org.apache.commons.math3.util.FastMath;
import org.junit.After;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;

public class ContinuousOutputModelTest {

  public ContinuousOutputModelTest() {
    pb    = null;
    integ = null;
  }

  @Test
  public void testBoundaries() throws DimensionMismatchException, NumberIsTooSmallException, MaxCountExceededException, NoBracketingException {
    integ.addStepHandler(new ContinuousOutputModel());
    integ.integrate(pb,
                    pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);
    ContinuousOutputModel cm = (ContinuousOutputModel) integ.getStepHandlers().iterator().next();
    cm.setInterpolatedTime(2.0 * pb.getInitialTime() - pb.getFinalTime());
    cm.setInterpolatedTime(2.0 * pb.getFinalTime() - pb.getInitialTime());
    cm.setInterpolatedTime(0.5 * (pb.getFinalTime() + pb.getInitialTime()));
  }

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

    ContinuousOutputModel cm = new ContinuousOutputModel();
    integ.addStepHandler(cm);
    integ.integrate(pb,
                    pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);

    Random random = new Random(347588535632l);
    double maxError    = 0.0;
    double maxErrorDot = 0.0;
    for (int i = 0; i < 1000; ++i) {
      double r = random.nextDouble();
      double time = r * pb.getInitialTime() + (1.0 - r) * pb.getFinalTime();
      cm.setInterpolatedTime(time);
      double[] interpolatedY    = cm.getInterpolatedState();
      double[] interpolatedYDot = cm.getInterpolatedDerivatives();
      double[] theoreticalY     = pb.computeTheoreticalState(time);
      double[] theoreticalYDot  = new double[pb.getDimension()];
      pb.doComputeDerivatives(time, theoreticalY, theoreticalYDot);
      double dx = interpolatedY[0] - theoreticalY[0];
      double dy = interpolatedY[1] - theoreticalY[1];
      double error = dx * dx + dy * dy;
      maxError = FastMath.max(maxError, error);
      double dxDot = interpolatedYDot[0] - theoreticalYDot[0];
      double dyDot = interpolatedYDot[1] - theoreticalYDot[1];
      double errorDot = dxDot * dxDot + dyDot * dyDot;
      maxErrorDot = FastMath.max(maxErrorDot, errorDot);
    }

    Assert.assertEquals(0.0, maxError,    1.0e-9);
    Assert.assertEquals(0.0, maxErrorDot, 4.0e-7);

  }

  @Test
  public void testModelsMerging() throws MaxCountExceededException, MathIllegalArgumentException {

      // theoretical solution: y[0] = cos(t), y[1] = sin(t)
      FirstOrderDifferentialEquations problem =
          new FirstOrderDifferentialEquations() {
              public void computeDerivatives(double t, double[] y, double[] dot) {
                  dot[0] = -y[1];
                  dot[1] =  y[0];
              }
              public int getDimension() {
                  return 2;
              }
          };

      // integrate backward from π to 0;
      ContinuousOutputModel cm1 = new ContinuousOutputModel();
      FirstOrderIntegrator integ1 =
          new DormandPrince853Integrator(0, 1.0, 1.0e-8, 1.0e-8);
      integ1.addStepHandler(cm1);
      integ1.integrate(problem, FastMath.PI, new double[] { -1.0, 0.0 },
                       0, new double[2]);

      // integrate backward from 2π to π
      ContinuousOutputModel cm2 = new ContinuousOutputModel();
      FirstOrderIntegrator integ2 =
          new DormandPrince853Integrator(0, 0.1, 1.0e-12, 1.0e-12);
      integ2.addStepHandler(cm2);
      integ2.integrate(problem, 2.0 * FastMath.PI, new double[] { 1.0, 0.0 },
                       FastMath.PI, new double[2]);

      // merge the two half circles
      ContinuousOutputModel cm = new ContinuousOutputModel();
      cm.append(cm2);
      cm.append(new ContinuousOutputModel());
      cm.append(cm1);

      // check circle
      Assert.assertEquals(2.0 * FastMath.PI, cm.getInitialTime(), 1.0e-12);
      Assert.assertEquals(0, cm.getFinalTime(), 1.0e-12);
      Assert.assertEquals(cm.getFinalTime(), cm.getInterpolatedTime(), 1.0e-12);
      for (double t = 0; t < 2.0 * FastMath.PI; t += 0.1) {
          cm.setInterpolatedTime(t);
          double[] y = cm.getInterpolatedState();
          Assert.assertEquals(FastMath.cos(t), y[0], 1.0e-7);
          Assert.assertEquals(FastMath.sin(t), y[1], 1.0e-7);
      }

  }

  @Test
  public void testErrorConditions() throws MaxCountExceededException, MathIllegalArgumentException {

      ContinuousOutputModel cm = new ContinuousOutputModel();
      cm.handleStep(buildInterpolator(0, new double[] { 0.0, 1.0, -2.0 }, 1), true);

      // dimension mismatch
      Assert.assertTrue(checkAppendError(cm, 1.0, new double[] { 0.0, 1.0 }, 2.0));

      // hole between time ranges
      Assert.assertTrue(checkAppendError(cm, 10.0, new double[] { 0.0, 1.0, -2.0 }, 20.0));

      // propagation direction mismatch
      Assert.assertTrue(checkAppendError(cm, 1.0, new double[] { 0.0, 1.0, -2.0 }, 0.0));

      // no errors
      Assert.assertFalse(checkAppendError(cm, 1.0, new double[] { 0.0, 1.0, -2.0 }, 2.0));

  }

  private boolean checkAppendError(ContinuousOutputModel cm,
                                   double t0, double[] y0, double t1)
      throws MaxCountExceededException, MathIllegalArgumentException {
      try {
          ContinuousOutputModel otherCm = new ContinuousOutputModel();
          otherCm.handleStep(buildInterpolator(t0, y0, t1), true);
          cm.append(otherCm);
      } catch(IllegalArgumentException iae) {
          return true; // there was an allowable error
      }
      return false; // no allowable error
  }

  private StepInterpolator buildInterpolator(double t0, double[] y0, double t1) {
      DummyStepInterpolator interpolator  = new DummyStepInterpolator(y0, new double[y0.length], t1 >= t0);
      interpolator.storeTime(t0);
      interpolator.shift();
      interpolator.storeTime(t1);
      return interpolator;
  }

  public void checkValue(double value, double reference) {
    Assert.assertTrue(FastMath.abs(value - reference) < 1.0e-10);
  }

  @Before
  public void setUp() {
    pb = new TestProblem3(0.9);
    double minStep = 0;
    double maxStep = pb.getFinalTime() - pb.getInitialTime();
    integ = new DormandPrince54Integrator(minStep, maxStep, 1.0e-8, 1.0e-8);
  }

  @After
  public void tearDown() {
    pb    = null;
    integ = null;
  }

  TestProblem3 pb;
  FirstOrderIntegrator integ;

}

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