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Java example source code file (TestProblemHandler.java)

This example Java source code file (TestProblemHandler.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

maxcountexceededexception, odeintegrator, stephandler, testproblemabstract, testproblemhandler

The TestProblemHandler.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 org.apache.commons.math3.exception.MaxCountExceededException;
import org.apache.commons.math3.ode.sampling.StepHandler;
import org.apache.commons.math3.ode.sampling.StepInterpolator;
import org.apache.commons.math3.util.FastMath;

/**
 * This class is used to handle steps for the test problems
 * integrated during the junit tests for the ODE integrators.
 */
public class TestProblemHandler
  implements StepHandler {

  /** Associated problem. */
  private TestProblemAbstract problem;

  /** Maximal errors encountered during the integration. */
  private double maxValueError;
  private double maxTimeError;

  /** Error at the end of the integration. */
  private double lastError;

  /** Time at the end of integration. */
  private double lastTime;

  /** ODE solver used. */
  private ODEIntegrator integrator;

  /** Expected start for step. */
  private double expectedStepStart;

  /**
   * Simple constructor.
   * @param problem problem for which steps should be handled
   * @param integrator ODE solver used
   */
  public TestProblemHandler(TestProblemAbstract problem, ODEIntegrator integrator) {
    this.problem = problem;
    this.integrator = integrator;
    maxValueError = 0;
    maxTimeError  = 0;
    lastError     = 0;
    expectedStepStart = Double.NaN;
  }

  public void init(double t0, double[] y0, double t) {
    maxValueError = 0;
    maxTimeError  = 0;
    lastError     = 0;
    expectedStepStart = Double.NaN;
  }

  public void handleStep(StepInterpolator interpolator, boolean isLast) throws MaxCountExceededException {

    double start = integrator.getCurrentStepStart();
    if (FastMath.abs((start - problem.getInitialTime()) / integrator.getCurrentSignedStepsize()) > 0.001) {
        // multistep integrators do not handle the first steps themselves
        // so we have to make sure the integrator we look at has really started its work
        if (!Double.isNaN(expectedStepStart)) {
            // the step should either start at the end of the integrator step
            // or at an event if the step is split into several substeps
            double stepError = FastMath.max(maxTimeError, FastMath.abs(start - expectedStepStart));
            for (double eventTime : problem.getTheoreticalEventsTimes()) {
                stepError = FastMath.min(stepError, FastMath.abs(start - eventTime));
            }
            maxTimeError = FastMath.max(maxTimeError, stepError);
        }
        expectedStepStart = start + integrator.getCurrentSignedStepsize();
    }


    double pT = interpolator.getPreviousTime();
    double cT = interpolator.getCurrentTime();
    double[] errorScale = problem.getErrorScale();

    // store the error at the last step
    if (isLast) {
        double[] interpolatedY = interpolator.getInterpolatedState();
        double[] theoreticalY  = problem.computeTheoreticalState(cT);
        for (int i = 0; i < interpolatedY.length; ++i) {
            double error = FastMath.abs(interpolatedY[i] - theoreticalY[i]);
            lastError = FastMath.max(error, lastError);
        }
        lastTime = cT;
    }
    // walk through the step
    for (int k = 0; k <= 20; ++k) {

        double time = pT + (k * (cT - pT)) / 20;
        interpolator.setInterpolatedTime(time);
        double[] interpolatedY = interpolator.getInterpolatedState();
        double[] theoreticalY  = problem.computeTheoreticalState(interpolator.getInterpolatedTime());

        // update the errors
        for (int i = 0; i < interpolatedY.length; ++i) {
            double error = errorScale[i] * FastMath.abs(interpolatedY[i] - theoreticalY[i]);
            maxValueError = FastMath.max(error, maxValueError);
        }
    }

  }

  /**
   * Get the maximal value error encountered during integration.
   * @return maximal value error
   */
  public double getMaximalValueError() {
    return maxValueError;
  }

  /**
   * Get the maximal time error encountered during integration.
   * @return maximal time error
   */
  public double getMaximalTimeError() {
    return maxTimeError;
  }


  public int getCalls() {
      return problem.getCalls();
  }

  /**
   * Get the error at the end of the integration.
   * @return error at the end of the integration
   */
  public double getLastError() {
    return lastError;
  }

  /**
   * Get the time at the end of the integration.
   * @return time at the end of the integration.
   */
  public double getLastTime() {
    return lastTime;
  }

}

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