alvinalexander.com | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Commons Math example source code file (TestProblem4.java)

This example Commons Math source code file (TestProblem4.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

bounce, bounce, eventhandler, eventhandler, override, override, stop, testproblem4, testproblem4, testproblemabstract

The Commons Math TestProblem4.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;

import org.apache.commons.math.ode.events.EventHandler;

/**
 * This class is used in the junit tests for the ODE integrators.

 * <p>This specific problem is the following differential equation :
 * <pre>
 *    x'' = -x
 * </pre>
 * And when x decreases down to 0, the state should be changed as follows :
 * <pre>
 *   x' -> -x'
 * </pre>
 * The theoretical solution of this problem is x = |sin(t+a)|
 * </p>

 */
public class TestProblem4
  extends TestProblemAbstract {

  /** Serializable version identifier. */
  private static final long serialVersionUID = -5910438521889015745L;

  /** Time offset. */
  private double a;

  /** theoretical state */
  private double[] y;

  /** Simple constructor. */
  public TestProblem4() {
    super();
    a = 1.2;
    double[] y0 = { Math.sin(a), Math.cos(a) };
    setInitialConditions(0.0, y0);
    setFinalConditions(15);
    double[] errorScale = { 1.0, 0.0 };
    setErrorScale(errorScale);
    y = new double[y0.length];
  }

  /**
   * Copy constructor.
   * @param problem problem to copy
   */
  public TestProblem4(TestProblem4 problem) {
    super(problem);
    a = problem.a;
    y = problem.y.clone();
  }

  /** {@inheritDoc} */
  @Override
public TestProblem4 copy() {
    return new TestProblem4(this);
  }

  @Override
  public EventHandler[] getEventsHandlers() {
    return new EventHandler[] { new Bounce(), new Stop() };
  }

  @Override
  public void doComputeDerivatives(double t, double[] y, double[] yDot) {
    yDot[0] =  y[1];
    yDot[1] = -y[0];
  }

  @Override
  public double[] computeTheoreticalState(double t) {
    double sin = Math.sin(t + a);
    double cos = Math.cos(t + a);
    y[0] = Math.abs(sin);
    y[1] = (sin >= 0) ? cos : -cos;
    return y;
  }

  private static class Bounce implements EventHandler {

    private static final long serialVersionUID = 1356097180027801200L;
    private int sign;

    public Bounce() {
      sign = +1;
    }

    public double g(double t, double[] y) {
      return sign * y[0];
    }

    public int eventOccurred(double t, double[] y, boolean increasing) {
      // this sign change is needed because the state will be reset soon
      sign = -sign;
      return EventHandler.RESET_STATE;
    }

    public void resetState(double t, double[] y) {
      y[0] = -y[0];
      y[1] = -y[1];
    }

  }

  private static class Stop implements EventHandler {

    private static final long serialVersionUID = 6975050568227951931L;

    public Stop() {
    }

    public double g(double t, double[] y) {
      return t - 12.0;
    }

    public int eventOccurred(double t, double[] y, boolean increasing) {
      return EventHandler.STOP;
    }

    public void resetState(double t, double[] y) {
    }

  }

}

Other Commons Math examples (source code examples)

Here is a short list of links related to this Commons Math TestProblem4.java source code file:

... this post is sponsored by my books ...

#1 New Release!

FP Best Seller

 

new blog posts

 

Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.