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Commons Math example source code file (EulerStepInterpolatorTest.java)

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

Java - Commons Math tags/keywords

continuousoutputmodel, derivativeexception, derivativeexception, dummyintegrator, dummyintegrator, eulerintegrator, eulerstepinterpolator, eulerstepinterpolator, integratorexception, io, random, test, test, testproblem1, testproblem3, util

The Commons Math EulerStepInterpolatorTest.java 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.math.ode.nonstiff;

import static org.junit.Assert.assertTrue;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Random;

import org.apache.commons.math.ode.ContinuousOutputModel;
import org.apache.commons.math.ode.DerivativeException;
import org.apache.commons.math.ode.IntegratorException;
import org.apache.commons.math.ode.TestProblem1;
import org.apache.commons.math.ode.TestProblem3;
import org.apache.commons.math.ode.sampling.StepHandler;
import org.apache.commons.math.ode.sampling.StepInterpolatorTestUtils;
import org.junit.Test;

public class EulerStepInterpolatorTest {

  @Test
  public void noReset() throws DerivativeException {

    double[]   y    =   { 0.0, 1.0, -2.0 };
    double[][] yDot = { { 1.0, 2.0, -2.0 } };
    EulerStepInterpolator interpolator = new EulerStepInterpolator();
    interpolator.reinitialize(new DummyIntegrator(interpolator), y, yDot, true);
    interpolator.storeTime(0);
    interpolator.shift();
    interpolator.storeTime(1);

    double[] result = interpolator.getInterpolatedState();
    for (int i = 0; i < result.length; ++i) {
      assertTrue(Math.abs(result[i] - y[i]) < 1.0e-10);
    }

  }

  @Test
  public void interpolationAtBounds()
    throws DerivativeException {

    double   t0 = 0;
    double[] y0 = {0.0, 1.0, -2.0};

    double[] y = y0.clone();
    double[][] yDot = { new double[y0.length] };
    EulerStepInterpolator interpolator = new EulerStepInterpolator();
    interpolator.reinitialize(new DummyIntegrator(interpolator), y, yDot, true);
    interpolator.storeTime(t0);

    double dt = 1.0;
    y[0] =  1.0;
    y[1] =  3.0;
    y[2] = -4.0;
    yDot[0][0] = (y[0] - y0[0]) / dt;
    yDot[0][1] = (y[1] - y0[1]) / dt;
    yDot[0][2] = (y[2] - y0[2]) / dt;
    interpolator.shift();
    interpolator.storeTime(t0 + dt);

    interpolator.setInterpolatedTime(interpolator.getPreviousTime());
    double[] result = interpolator.getInterpolatedState();
    for (int i = 0; i < result.length; ++i) {
      assertTrue(Math.abs(result[i] - y0[i]) < 1.0e-10);
    }

    interpolator.setInterpolatedTime(interpolator.getCurrentTime());
    result = interpolator.getInterpolatedState();
    for (int i = 0; i < result.length; ++i) {
      assertTrue(Math.abs(result[i] - y[i]) < 1.0e-10);
    }

  }

  @Test
  public void interpolationInside()
  throws DerivativeException {

    double[]   y    =   { 1.0, 3.0, -4.0 };
    double[][] yDot = { { 1.0, 2.0, -2.0 } };
    EulerStepInterpolator interpolator = new EulerStepInterpolator();
    interpolator.reinitialize(new DummyIntegrator(interpolator), y, yDot, true);
    interpolator.storeTime(0);
    interpolator.shift();
    interpolator.storeTime(1);

    interpolator.setInterpolatedTime(0.1);
    double[] result = interpolator.getInterpolatedState();
    assertTrue(Math.abs(result[0] - 0.1) < 1.0e-10);
    assertTrue(Math.abs(result[1] - 1.2) < 1.0e-10);
    assertTrue(Math.abs(result[2] + 2.2) < 1.0e-10);

    interpolator.setInterpolatedTime(0.5);
    result = interpolator.getInterpolatedState();
    assertTrue(Math.abs(result[0] - 0.5) < 1.0e-10);
    assertTrue(Math.abs(result[1] - 2.0) < 1.0e-10);
    assertTrue(Math.abs(result[2] + 3.0) < 1.0e-10);

  }

  @Test
  public void derivativesConsistency()
  throws DerivativeException, IntegratorException {
    TestProblem3 pb = new TestProblem3();
    double step = (pb.getFinalTime() - pb.getInitialTime()) * 0.001;
    EulerIntegrator integ = new EulerIntegrator(step);
    StepInterpolatorTestUtils.checkDerivativesConsistency(integ, pb, 1.0e-10);
  }

  @Test
  public void serialization()
    throws DerivativeException, IntegratorException,
           IOException, ClassNotFoundException {

    TestProblem1 pb = new TestProblem1();
    double step = (pb.getFinalTime() - pb.getInitialTime()) * 0.001;
    EulerIntegrator integ = new EulerIntegrator(step);
    integ.addStepHandler(new ContinuousOutputModel());
    integ.integrate(pb,
                    pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);

    ByteArrayOutputStream bos = new ByteArrayOutputStream();
    ObjectOutputStream    oos = new ObjectOutputStream(bos);
    for (StepHandler handler : integ.getStepHandlers()) {
        oos.writeObject(handler);
    }

    ByteArrayInputStream  bis = new ByteArrayInputStream(bos.toByteArray());
    ObjectInputStream     ois = new ObjectInputStream(bis);
    ContinuousOutputModel cm  = (ContinuousOutputModel) ois.readObject();

    Random random = new Random(347588535632l);
    double maxError = 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[] theoreticalY  = pb.computeTheoreticalState(time);
      double dx = interpolatedY[0] - theoreticalY[0];
      double dy = interpolatedY[1] - theoreticalY[1];
      double error = dx * dx + dy * dy;
      if (error > maxError) {
        maxError = error;
      }
    }
    assertTrue(maxError < 0.001);

  }

  private static class DummyIntegrator extends RungeKuttaIntegrator {


      protected DummyIntegrator(RungeKuttaStepInterpolator prototype) {
          super("dummy", new double[0], new double[0][0], new double[0], prototype, Double.NaN);
      }

  }

}

Other Commons Math examples (source code examples)

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