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Java example source code file (OverlappingEventsTest.java)

This example Java source code file (OverlappingEventsTest.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

action, arraylist, basesecantsolver, dimensionmismatchexception, event, event_times1, eventhandler, list, maxcountexceededexception, nobracketingexception, numberistoosmallexception, overlappingeventstest, pegasussolver, test, util

The OverlappingEventsTest.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.events;

import java.util.ArrayList;
import java.util.List;

import org.apache.commons.math3.analysis.solvers.BaseSecantSolver;
import org.apache.commons.math3.analysis.solvers.PegasusSolver;
import org.apache.commons.math3.exception.DimensionMismatchException;
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.FirstOrderDifferentialEquations;
import org.apache.commons.math3.ode.FirstOrderIntegrator;
import org.apache.commons.math3.ode.nonstiff.DormandPrince853Integrator;
import org.junit.Assert;
import org.junit.Test;

/** Tests for overlapping state events. Also tests an event function that does
 * not converge to zero, but does have values of opposite sign around its root.
 */
public class OverlappingEventsTest implements FirstOrderDifferentialEquations {

    /** Expected event times for first event. */
    private static final double[] EVENT_TIMES1 = {1.0, 2.0, 3.0, 4.0, 5.0, 6.0,
                                                  7.0, 8.0, 9.0};

    /** Expected event times for second event. */
    private static final double[] EVENT_TIMES2 = {0.5, 1.0, 1.5, 2.0, 2.5, 3.0,
                                                  3.5, 4.0, 4.5, 5.0, 5.5, 6.0,
                                                  6.5, 7.0, 7.5, 8.0, 8.5, 9.0,
                                                  9.5};

    /** Test for events that occur at the exact same time, but due to numerical
     * calculations occur very close together instead. Uses event type 0. See
     * {@link org.apache.commons.math3.ode.events.EventHandler#g(double, double[])
     * EventHandler.g(double, double[])}.
     */
    @Test
    public void testOverlappingEvents0()
        throws DimensionMismatchException, NumberIsTooSmallException,
               MaxCountExceededException, NoBracketingException {
        test(0);
    }

    /** Test for events that occur at the exact same time, but due to numerical
     * calculations occur very close together instead. Uses event type 1. See
     * {@link org.apache.commons.math3.ode.events.EventHandler#g(double, double[])
     * EventHandler.g(double, double[])}.
     */
    @Test
    public void testOverlappingEvents1()
        throws DimensionMismatchException, NumberIsTooSmallException,
               MaxCountExceededException, NoBracketingException {
        test(1);
    }

    /** Test for events that occur at the exact same time, but due to numerical
     * calculations occur very close together instead.
     * @param eventType the type of events to use. See
     * {@link org.apache.commons.math3.ode.events.EventHandler#g(double, double[])
     * EventHandler.g(double, double[])}.
     */
    public void test(int eventType)
        throws DimensionMismatchException, NumberIsTooSmallException,
               MaxCountExceededException, NoBracketingException {
        double e = 1e-15;
        FirstOrderIntegrator integrator = new DormandPrince853Integrator(e, 100.0, 1e-7, 1e-7);
        BaseSecantSolver rootSolver = new PegasusSolver(e, e);
        EventHandler evt1 = new Event(0, eventType);
        EventHandler evt2 = new Event(1, eventType);
        integrator.addEventHandler(evt1, 0.1, e, 999, rootSolver);
        integrator.addEventHandler(evt2, 0.1, e, 999, rootSolver);
        double t = 0.0;
        double tEnd = 10.0;
        double[] y = {0.0, 0.0};
        List<Double> events1 = new ArrayList();
        List<Double> events2 = new ArrayList();
        while (t < tEnd) {
            t = integrator.integrate(this, t, y, tEnd, y);
            //System.out.println("t=" + t + ",\t\ty=[" + y[0] + "," + y[1] + "]");

            if (y[0] >= 1.0) {
                y[0] = 0.0;
                events1.add(t);
                //System.out.println("Event 1 @ t=" + t);
            }
            if (y[1] >= 1.0) {
                y[1] = 0.0;
                events2.add(t);
                //System.out.println("Event 2 @ t=" + t);
            }
        }
        Assert.assertEquals(EVENT_TIMES1.length, events1.size());
        Assert.assertEquals(EVENT_TIMES2.length, events2.size());
        for(int i = 0; i < EVENT_TIMES1.length; i++) {
            Assert.assertEquals(EVENT_TIMES1[i], events1.get(i), 1e-7);
        }
        for(int i = 0; i < EVENT_TIMES2.length; i++) {
            Assert.assertEquals(EVENT_TIMES2[i], events2.get(i), 1e-7);
        }
        //System.out.println();
    }

    /** {@inheritDoc} */
    public int getDimension() {
        return 2;
    }

    /** {@inheritDoc} */
    public void computeDerivatives(double t, double[] y, double[] yDot) {
        yDot[0] = 1.0;
        yDot[1] = 2.0;
    }

    /** State events for this unit test. */
    private class Event implements EventHandler {
        /** The index of the continuous variable to use. */
        private final int idx;

        /** The event type to use. See {@link #g}. */
        private final int eventType;

        /** Constructor for the {@link Event} class.
         * @param idx the index of the continuous variable to use
         * @param eventType the type of event to use. See {@link #g}
         */
        public Event(int idx, int eventType) {
            this.idx = idx;
            this.eventType = eventType;
        }

        /** {@inheritDoc} */
        public void init(double t0, double[] y0, double t) {
        }

        /** {@inheritDoc} */
        public double g(double t, double[] y) {
            return (eventType == 0) ? y[idx] >= 1.0 ? 1.0 : -1.0
                                    : y[idx] - 1.0;
        }

        /** {@inheritDoc} */
        public Action eventOccurred(double t, double[] y, boolean increasing) {
            return Action.STOP;
        }

        /** {@inheritDoc} */
        public void resetState(double t, double[] y) {
            // Never called.
        }
    }
}

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