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Java example source code file (TestFieldProblemHandler.java)

This example Java source code file (TestFieldProblemHandler.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

fieldstephandler, firstorderfieldintegrator, maxcountexceededexception, realfieldelement, testfieldproblemabstract, testfieldproblemhandler

The TestFieldProblemHandler.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.RealFieldElement;
import org.apache.commons.math3.exception.MaxCountExceededException;
import org.apache.commons.math3.ode.sampling.FieldStepHandler;
import org.apache.commons.math3.ode.sampling.FieldStepInterpolator;
import org.apache.commons.math3.util.MathUtils;

/**
 * This class is used to handle steps for the test problems
 * integrated during the junit tests for the ODE integrators.
 * @param <T> the type of the field elements
 */
public class TestFieldProblemHandler<T extends RealFieldElement
    implements FieldStepHandler<T> {

    /** Associated problem. */
    private TestFieldProblemAbstract<T> problem;

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

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

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

    /** ODE solver used. */
    private FirstOrderFieldIntegrator<T> integrator;

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

    /**
     * Simple constructor.
     * @param problem problem for which steps should be handled
     * @param integrator ODE solver used
     */
    public TestFieldProblemHandler(TestFieldProblemAbstract<T> problem, FirstOrderFieldIntegrator integrator) {
        this.problem      = problem;
        this.integrator   = integrator;
        maxValueError     = problem.getField().getZero();
        maxTimeError      = problem.getField().getZero();
        lastError         = problem.getField().getZero();
        expectedStepStart = null;
    }

    public void init(FieldODEStateAndDerivative<T> state0, T t) {
        maxValueError     = problem.getField().getZero();
        maxTimeError      = problem.getField().getZero();
        lastError         = problem.getField().getZero();
        expectedStepStart = null;
    }

    public void handleStep(FieldStepInterpolator<T> interpolator, boolean isLast) throws MaxCountExceededException {

        T start = integrator.getCurrentStepStart().getTime();
        if (start.subtract(problem.getInitialState().getTime()).divide(integrator.getCurrentSignedStepsize()).abs().getReal() > 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 (expectedStepStart != null) {
                // the step should either start at the end of the integrator step
                // or at an event if the step is split into several substeps
                T stepError = MathUtils.max(maxTimeError, start.subtract(expectedStepStart).abs());
                for (T eventTime : problem.getTheoreticalEventsTimes()) {
                    stepError = MathUtils.min(stepError, start.subtract(eventTime).abs());
                }
                maxTimeError = MathUtils.max(maxTimeError, stepError);
            }
            expectedStepStart = start.add(integrator.getCurrentSignedStepsize());
        }

        T pT = interpolator.getPreviousState().getTime();
        T cT = interpolator.getCurrentState().getTime();
        T[] errorScale = problem.getErrorScale();

        // store the error at the last step
        if (isLast) {
            T[] interpolatedY = interpolator.getInterpolatedState(cT).getState();
            T[] theoreticalY  = problem.computeTheoreticalState(cT);
            for (int i = 0; i < interpolatedY.length; ++i) {
                T error = interpolatedY[i].subtract(theoreticalY[i]).abs();
                lastError = MathUtils.max(error, lastError);
            }
            lastTime = cT;
        }

        // walk through the step
        for (int k = 0; k <= 20; ++k) {

            T time = pT.add(cT.subtract(pT).multiply(k).divide(20));
            T[] interpolatedY = interpolator.getInterpolatedState(time).getState();
            T[] theoreticalY  = problem.computeTheoreticalState(time);

            // update the errors
            for (int i = 0; i < interpolatedY.length; ++i) {
                T error = errorScale[i].multiply(interpolatedY[i].subtract(theoreticalY[i]).abs());
                maxValueError = MathUtils.max(error, maxValueError);
            }
        }
    }

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

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

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

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

}

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