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Java example source code file (StepInterpolatorTestUtils.java)

This example Java source code file (StepInterpolatorTestUtils.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

dimensionmismatchexception, fieldexpandableode, fieldstephandler, firstorderfieldintegrator, firstorderintegrator, maxcountexceededexception, nobracketingexception, numberistoosmallexception, realfieldelement, stephandler, stepinterpolatortestutils, testfieldproblemabstract, testproblemabstract

The StepInterpolatorTestUtils.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.sampling;


import org.apache.commons.math3.RealFieldElement;
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.FieldExpandableODE;
import org.apache.commons.math3.ode.FirstOrderFieldIntegrator;
import org.apache.commons.math3.ode.FieldODEStateAndDerivative;
import org.apache.commons.math3.ode.FirstOrderIntegrator;
import org.apache.commons.math3.ode.TestFieldProblemAbstract;
import org.apache.commons.math3.ode.TestProblemAbstract;
import org.apache.commons.math3.util.FastMath;
import org.junit.Assert;

public class StepInterpolatorTestUtils {

    public static void checkDerivativesConsistency(final FirstOrderIntegrator integrator,
                                                   final TestProblemAbstract problem,
                                                   final double finiteDifferencesRatio,
                                                   final double threshold)
        throws DimensionMismatchException, NumberIsTooSmallException,
               MaxCountExceededException, NoBracketingException {
        integrator.addStepHandler(new StepHandler() {

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

                final double dt = interpolator.getCurrentTime() - interpolator.getPreviousTime();
                final double h  = finiteDifferencesRatio * dt;
                final double t  = interpolator.getCurrentTime() - 0.3 * dt;

                if (FastMath.abs(h) < 10 * FastMath.ulp(t)) {
                    return;
                }

                interpolator.setInterpolatedTime(t - 4 * h);
                final double[] yM4h = interpolator.getInterpolatedState().clone();
                interpolator.setInterpolatedTime(t - 3 * h);
                final double[] yM3h = interpolator.getInterpolatedState().clone();
                interpolator.setInterpolatedTime(t - 2 * h);
                final double[] yM2h = interpolator.getInterpolatedState().clone();
                interpolator.setInterpolatedTime(t - h);
                final double[] yM1h = interpolator.getInterpolatedState().clone();
                interpolator.setInterpolatedTime(t + h);
                final double[] yP1h = interpolator.getInterpolatedState().clone();
                interpolator.setInterpolatedTime(t + 2 * h);
                final double[] yP2h = interpolator.getInterpolatedState().clone();
                interpolator.setInterpolatedTime(t + 3 * h);
                final double[] yP3h = interpolator.getInterpolatedState().clone();
                interpolator.setInterpolatedTime(t + 4 * h);
                final double[] yP4h = interpolator.getInterpolatedState().clone();

                interpolator.setInterpolatedTime(t);
                final double[] yDot = interpolator.getInterpolatedDerivatives();

                for (int i = 0; i < yDot.length; ++i) {
                    final double approYDot = ( -3 * (yP4h[i] - yM4h[i]) +
                                               32 * (yP3h[i] - yM3h[i]) +
                                             -168 * (yP2h[i] - yM2h[i]) +
                                              672 * (yP1h[i] - yM1h[i])) / (840 * h);
                    Assert.assertEquals("" + (approYDot - yDot[i]), approYDot, yDot[i], threshold);
                }

            }

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

        });

        integrator.integrate(problem,
                             problem.getInitialTime(), problem.getInitialState(),
                             problem.getFinalTime(), new double[problem.getDimension()]);

    }

    public static <T extends RealFieldElement void checkDerivativesConsistency(final FirstOrderFieldIntegrator integrator,
                                                                                   final TestFieldProblemAbstract<T> problem,
                                                                                   final double threshold) {
        integrator.addStepHandler(new FieldStepHandler<T>() {

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

                final T h = interpolator.getCurrentState().getTime().subtract(interpolator.getPreviousState().getTime()).multiply(0.001);
                final T t = interpolator.getCurrentState().getTime().subtract(h.multiply(300));

                if (h.abs().subtract(FastMath.ulp(t.getReal()) * 10).getReal() < 0) {
                    return;
                }

                final T[] yM4h = interpolator.getInterpolatedState(t.add(h.multiply(-4))).getState();
                final T[] yM3h = interpolator.getInterpolatedState(t.add(h.multiply(-3))).getState();
                final T[] yM2h = interpolator.getInterpolatedState(t.add(h.multiply(-2))).getState();
                final T[] yM1h = interpolator.getInterpolatedState(t.add(h.multiply(-1))).getState();
                final T[] yP1h = interpolator.getInterpolatedState(t.add(h.multiply( 1))).getState();
                final T[] yP2h = interpolator.getInterpolatedState(t.add(h.multiply( 2))).getState();
                final T[] yP3h = interpolator.getInterpolatedState(t.add(h.multiply( 3))).getState();
                final T[] yP4h = interpolator.getInterpolatedState(t.add(h.multiply( 4))).getState();

                final T[] yDot = interpolator.getInterpolatedState(t).getDerivative();

                for (int i = 0; i < yDot.length; ++i) {
                    final T approYDot =     yP4h[i].subtract(yM4h[i]).multiply(  -3).
                                        add(yP3h[i].subtract(yM3h[i]).multiply(  32)).
                                        add(yP2h[i].subtract(yM2h[i]).multiply(-168)).
                                        add(yP1h[i].subtract(yM1h[i]).multiply( 672)).
                                        divide(h.multiply(840));
                    Assert.assertEquals(approYDot.getReal(), yDot[i].getReal(), threshold);
                }

            }

            public void init(FieldODEStateAndDerivative<T> state0, T t) {
            }

        });

        integrator.integrate(new FieldExpandableODE<T>(problem), problem.getInitialState(), problem.getFinalTime());

    }
}

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