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Java example source code file (EventStateTest.java)

This example Java source code file (EventStateTest.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, closeeventsgenerator, dimensionmismatchexception, dormandprince853integrator, eventhandler, eventstate, expandablestatefulode, firstorderdifferentialequations, maxcountexceededexception, nobracketingexception, numberistoosmallexception, resettingevent, secondarystateevent, test

The EventStateTest.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 org.apache.commons.math3.analysis.solvers.BrentSolver;
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.ExpandableStatefulODE;
import org.apache.commons.math3.ode.FirstOrderDifferentialEquations;
import org.apache.commons.math3.ode.SecondaryEquations;
import org.apache.commons.math3.ode.nonstiff.DormandPrince853Integrator;
import org.apache.commons.math3.ode.nonstiff.LutherIntegrator;
import org.apache.commons.math3.ode.sampling.AbstractStepInterpolator;
import org.apache.commons.math3.ode.sampling.DummyStepInterpolator;
import org.junit.Assert;
import org.junit.Test;

public class EventStateTest {

    // JIRA: MATH-322
    @Test
    public void closeEvents() throws MaxCountExceededException, NoBracketingException {

        final double r1  = 90.0;
        final double r2  = 135.0;
        final double gap = r2 - r1;

        final double tolerance = 0.1;
        EventState es = new EventState(new CloseEventsGenerator(r1, r2), 1.5 * gap,
                                       tolerance, 100,
                                       new BrentSolver(tolerance));
        es.setExpandable(new ExpandableStatefulODE(new FirstOrderDifferentialEquations() {
            public int getDimension() {
                return 0;
            }
            public void computeDerivatives(double t, double[] y, double[] yDot) {
            }
        }));

        AbstractStepInterpolator interpolator =
            new DummyStepInterpolator(new double[0], new double[0], true);
        interpolator.storeTime(r1 - 2.5 * gap);
        interpolator.shift();
        interpolator.storeTime(r1 - 1.5 * gap);
        es.reinitializeBegin(interpolator);

        interpolator.shift();
        interpolator.storeTime(r1 - 0.5 * gap);
        Assert.assertFalse(es.evaluateStep(interpolator));

        interpolator.shift();
        interpolator.storeTime(0.5 * (r1 + r2));
        Assert.assertTrue(es.evaluateStep(interpolator));
        Assert.assertEquals(r1, es.getEventTime(), tolerance);
        es.stepAccepted(es.getEventTime(), new double[0]);

        interpolator.shift();
        interpolator.storeTime(r2 + 0.4 * gap);
        Assert.assertTrue(es.evaluateStep(interpolator));
        Assert.assertEquals(r2, es.getEventTime(), tolerance);

    }

    // Jira: MATH-695
    @Test
    public void testIssue695()
        throws DimensionMismatchException, NumberIsTooSmallException,
               MaxCountExceededException, NoBracketingException {

        FirstOrderDifferentialEquations equation = new FirstOrderDifferentialEquations() {

            public int getDimension() {
                return 1;
            }

            public void computeDerivatives(double t, double[] y, double[] yDot) {
                yDot[0] = 1.0;
            }
        };

        DormandPrince853Integrator integrator = new DormandPrince853Integrator(0.001, 1000, 1.0e-14, 1.0e-14);
        integrator.addEventHandler(new ResettingEvent(10.99), 0.1, 1.0e-9, 1000);
        integrator.addEventHandler(new ResettingEvent(11.01), 0.1, 1.0e-9, 1000);
        integrator.setInitialStepSize(3.0);

        double target = 30.0;
        double[] y = new double[1];
        double tEnd = integrator.integrate(equation, 0.0, y, target, y);
        Assert.assertEquals(target, tEnd, 1.0e-10);
        Assert.assertEquals(32.0, y[0], 1.0e-10);

    }

    private static class ResettingEvent implements EventHandler {

        private static double lastTriggerTime = Double.NEGATIVE_INFINITY;
        private final double tEvent;

        public ResettingEvent(final double tEvent) {
            this.tEvent = tEvent;
        }

        public void init(double t0, double[] y0, double t) {
        }

        public double g(double t, double[] y) {
            // the bug corresponding to issue 695 causes the g function
            // to be called at obsolete times t despite an event
            // occurring later has already been triggered.
            // When this occurs, the following assertion is violated
            Assert.assertTrue("going backard in time! (" + t + " < " + lastTriggerTime + ")",
                              t >= lastTriggerTime);
            return t - tEvent;
        }

        public Action eventOccurred(double t, double[] y, boolean increasing) {
            // remember in a class variable when the event was triggered
            lastTriggerTime = t;
            return Action.RESET_STATE;
        }

        public void resetState(double t, double[] y) {
            y[0] += 1.0;
        }

    }

    // Jira: MATH-965
    @Test
    public void testIssue965()
        throws DimensionMismatchException, NumberIsTooSmallException,
               MaxCountExceededException, NoBracketingException {

        ExpandableStatefulODE equation =
                new ExpandableStatefulODE(new FirstOrderDifferentialEquations() {

            public int getDimension() {
                return 1;
            }

            public void computeDerivatives(double t, double[] y, double[] yDot) {
                yDot[0] = 2.0;
            }
        });
        equation.setTime(0.0);
        equation.setPrimaryState(new double[1]);
        equation.addSecondaryEquations(new SecondaryEquations() {

            public int getDimension() {
                return 1;
            }

            public void computeDerivatives(double t, double[] primary,
                                           double[] primaryDot, double[] secondary,
                                           double[] secondaryDot) {
                secondaryDot[0] = -3.0;
            }
        });
        int index = equation.getSecondaryMappers()[0].getFirstIndex();

        DormandPrince853Integrator integrator = new DormandPrince853Integrator(0.001, 1000, 1.0e-14, 1.0e-14);
        integrator.addEventHandler(new SecondaryStateEvent(index, -3.0), 0.1, 1.0e-9, 1000);
        integrator.setInitialStepSize(3.0);

        integrator.integrate(equation, 30.0);
        Assert.assertEquals( 1.0, equation.getTime(), 1.0e-10);
        Assert.assertEquals( 2.0, equation.getPrimaryState()[0], 1.0e-10);
        Assert.assertEquals(-3.0, equation.getSecondaryState(0)[0], 1.0e-10);

    }

    private static class SecondaryStateEvent implements EventHandler {

        private int index;
        private final double target;

        public SecondaryStateEvent(final int index, final double target) {
            this.index  = index;
            this.target = target;
        }

        public void init(double t0, double[] y0, double t) {
        }

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

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

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

    }

    @Test
    public void testEventsCloserThanThreshold()
        throws DimensionMismatchException, NumberIsTooSmallException,
               MaxCountExceededException, NoBracketingException {

        FirstOrderDifferentialEquations equation = new FirstOrderDifferentialEquations() {

            public int getDimension() {
                return 1;
            }

            public void computeDerivatives(double t, double[] y, double[] yDot) {
                yDot[0] = 1.0;
            }
        };

        LutherIntegrator integrator = new LutherIntegrator(20.0);
        CloseEventsGenerator eventsGenerator =
                        new CloseEventsGenerator(9.0 - 1.0 / 128, 9.0 + 1.0 / 128);
        integrator.addEventHandler(eventsGenerator, 1.0, 0.02, 1000);
        double[] y = new double[1];
        double tEnd = integrator.integrate(equation, 0.0, y, 100.0, y);
        Assert.assertEquals( 2, eventsGenerator.getCount());
        Assert.assertEquals( 9.0 + 1.0 / 128, tEnd, 1.0 / 32.0);

    }

    private class CloseEventsGenerator implements EventHandler {

        final double r1;
        final double r2;
        int count;

        public CloseEventsGenerator(final double r1, final double r2) {
            this.r1    = r1;
            this.r2    = r2;
            this.count = 0;
        }

        public void init(double t0, double[] y0, double t) {
        }

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

        public double g(double t, double[] y) {
            return (t - r1) * (r2 - t);
        }

        public Action eventOccurred(double t, double[] y, boolean increasing) {
            return ++count < 2 ? Action.CONTINUE : Action.STOP;
        }

        public int getCount() {
            return count;
        }

    }

}

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