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Commons Math example source code file (MidpointIntegratorTest.java)

This example Commons Math source code file (MidpointIntegratorTest.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons Math tags/keywords

derivativeexception, derivativeexception, firstorderintegrator, firstorderintegrator, integratorexception, midpointintegrator, midpointintegratortest, testcase, testproblem1, testproblem1, testproblem5, testproblemabstract, testproblemhandler, testproblemhandler

The Commons Math MidpointIntegratorTest.java 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.math.ode.nonstiff;

import junit.framework.*;

import org.apache.commons.math.ode.DerivativeException;
import org.apache.commons.math.ode.FirstOrderDifferentialEquations;
import org.apache.commons.math.ode.FirstOrderIntegrator;
import org.apache.commons.math.ode.IntegratorException;
import org.apache.commons.math.ode.TestProblem1;
import org.apache.commons.math.ode.TestProblem5;
import org.apache.commons.math.ode.TestProblemAbstract;
import org.apache.commons.math.ode.TestProblemFactory;
import org.apache.commons.math.ode.TestProblemHandler;
import org.apache.commons.math.ode.events.EventHandler;
import org.apache.commons.math.ode.nonstiff.MidpointIntegrator;
import org.apache.commons.math.ode.sampling.StepHandler;
import org.apache.commons.math.ode.sampling.StepInterpolator;

public class MidpointIntegratorTest
  extends TestCase {

  public MidpointIntegratorTest(String name) {
    super(name);
  }

  public void testDimensionCheck() {
    try  {
      TestProblem1 pb = new TestProblem1();
      new MidpointIntegrator(0.01).integrate(pb,
                                             0.0, new double[pb.getDimension()+10],
                                             1.0, new double[pb.getDimension()+10]);
        fail("an exception should have been thrown");
    } catch(DerivativeException de) {
      fail("wrong exception caught");
    } catch(IntegratorException ie) {
    }
  }

  public void testDecreasingSteps()
    throws DerivativeException, IntegratorException  {

    TestProblemAbstract[] problems = TestProblemFactory.getProblems();
    for (int k = 0; k < problems.length; ++k) {

      double previousError = Double.NaN;
      for (int i = 4; i < 10; ++i) {

        TestProblemAbstract pb = problems[k].copy();
        double step = (pb.getFinalTime() - pb.getInitialTime())
          * Math.pow(2.0, -i);
        FirstOrderIntegrator integ = new MidpointIntegrator(step);
        TestProblemHandler handler = new TestProblemHandler(pb, integ);
        integ.addStepHandler(handler);
        EventHandler[] functions = pb.getEventsHandlers();
        for (int l = 0; l < functions.length; ++l) {
          integ.addEventHandler(functions[l],
                                     Double.POSITIVE_INFINITY, 1.0e-6 * step, 1000);
        }
        double stopTime = integ.integrate(pb,
                                          pb.getInitialTime(), pb.getInitialState(),
                                          pb.getFinalTime(), new double[pb.getDimension()]);
        if (functions.length == 0) {
            assertEquals(pb.getFinalTime(), stopTime, 1.0e-10);
        }

        double error = handler.getMaximalValueError();
        if (i > 4) {
          assertTrue(error < Math.abs(previousError));
        }
        previousError = error;
        assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);

      }

    }

  }

  public void testSmallStep()
    throws DerivativeException, IntegratorException {

    TestProblem1 pb  = new TestProblem1();
    double step = (pb.getFinalTime() - pb.getInitialTime()) * 0.001;

    FirstOrderIntegrator integ = new MidpointIntegrator(step);
    TestProblemHandler handler = new TestProblemHandler(pb, integ);
    integ.addStepHandler(handler);
    integ.integrate(pb,
                    pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);

    assertTrue(handler.getLastError() < 2.0e-7);
    assertTrue(handler.getMaximalValueError() < 1.0e-6);
    assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);
    assertEquals("midpoint", integ.getName());

  }

  public void testBigStep()
    throws DerivativeException, IntegratorException {

    TestProblem1 pb  = new TestProblem1();
    double step = (pb.getFinalTime() - pb.getInitialTime()) * 0.2;

    FirstOrderIntegrator integ = new MidpointIntegrator(step);
    TestProblemHandler handler = new TestProblemHandler(pb, integ);
    integ.addStepHandler(handler);
    integ.integrate(pb,
                    pb.getInitialTime(), pb.getInitialState(),
                    pb.getFinalTime(), new double[pb.getDimension()]);

    assertTrue(handler.getLastError() > 0.01);
    assertTrue(handler.getMaximalValueError() > 0.05);
    assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);

  }

  public void testBackward()
      throws DerivativeException, IntegratorException {

      TestProblem5 pb = new TestProblem5();
      double step = Math.abs(pb.getFinalTime() - pb.getInitialTime()) * 0.001;

      FirstOrderIntegrator integ = new MidpointIntegrator(step);
      TestProblemHandler handler = new TestProblemHandler(pb, integ);
      integ.addStepHandler(handler);
      integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(),
                      pb.getFinalTime(), new double[pb.getDimension()]);

      assertTrue(handler.getLastError() < 6.0e-4);
      assertTrue(handler.getMaximalValueError() < 6.0e-4);
      assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);
      assertEquals("midpoint", integ.getName());
  }

  public void testStepSize()
    throws DerivativeException, IntegratorException {
      final double step = 1.23456;
      FirstOrderIntegrator integ = new MidpointIntegrator(step);
      integ.addStepHandler(new StepHandler() {
          public void handleStep(StepInterpolator interpolator, boolean isLast) {
              if (! isLast) {
                  assertEquals(step,
                               interpolator.getCurrentTime() - interpolator.getPreviousTime(),
                               1.0e-12);
              }
          }
          public boolean requiresDenseOutput() {
              return false;
          }
          public void reset() {
          }
      });
      integ.integrate(new FirstOrderDifferentialEquations() {
          private static final long serialVersionUID = 0L;
          public void computeDerivatives(double t, double[] y, double[] dot) {
              dot[0] = 1.0;
          }
          public int getDimension() {
              return 1;
          }
      }, 0.0, new double[] { 0.0 }, 5.0, new double[1]);
  }

}

Other Commons Math examples (source code examples)

Here is a short list of links related to this Commons Math MidpointIntegratorTest.java source code file:

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