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* 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
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* 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.
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package org.apache.commons.math3.ode.nonstiff;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.Random;
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.ContinuousOutputModel;
import org.apache.commons.math3.ode.EquationsMapper;
import org.apache.commons.math3.ode.TestProblem1;
import org.apache.commons.math3.ode.TestProblem3;
import org.apache.commons.math3.ode.sampling.StepHandler;
import org.apache.commons.math3.ode.sampling.StepInterpolatorTestUtils;
import org.apache.commons.math3.util.FastMath;
import org.junit.Assert;
import org.junit.Test;
public class EulerStepInterpolatorTest {
@Test
public void noReset() throws MaxCountExceededException {
double[] y = { 0.0, 1.0, -2.0 };
double[][] yDot = { { 1.0, 2.0, -2.0 } };
EulerStepInterpolator interpolator = new EulerStepInterpolator();
interpolator.reinitialize(new DummyIntegrator(interpolator), y, yDot, true,
new EquationsMapper(0, y.length),
new EquationsMapper[0]);
interpolator.storeTime(0);
interpolator.shift();
interpolator.storeTime(1);
double[] result = interpolator.getInterpolatedState();
for (int i = 0; i < result.length; ++i) {
Assert.assertTrue(FastMath.abs(result[i] - y[i]) < 1.0e-10);
}
}
@Test
public void interpolationAtBounds() throws MaxCountExceededException {
double t0 = 0;
double[] y0 = {0.0, 1.0, -2.0};
double[] y = y0.clone();
double[][] yDot = { new double[y0.length] };
EulerStepInterpolator interpolator = new EulerStepInterpolator();
interpolator.reinitialize(new DummyIntegrator(interpolator), y, yDot, true,
new EquationsMapper(0, y.length),
new EquationsMapper[0]);
interpolator.storeTime(t0);
double dt = 1.0;
interpolator.shift();
y[0] = 1.0;
y[1] = 3.0;
y[2] = -4.0;
yDot[0][0] = (y[0] - y0[0]) / dt;
yDot[0][1] = (y[1] - y0[1]) / dt;
yDot[0][2] = (y[2] - y0[2]) / dt;
interpolator.storeTime(t0 + dt);
interpolator.setInterpolatedTime(interpolator.getPreviousTime());
double[] result = interpolator.getInterpolatedState();
for (int i = 0; i < result.length; ++i) {
Assert.assertTrue(FastMath.abs(result[i] - y0[i]) < 1.0e-10);
}
interpolator.setInterpolatedTime(interpolator.getCurrentTime());
result = interpolator.getInterpolatedState();
for (int i = 0; i < result.length; ++i) {
Assert.assertTrue(FastMath.abs(result[i] - y[i]) < 1.0e-10);
}
}
@Test
public void interpolationInside() throws MaxCountExceededException {
double[] y = { 0.0, 1.0, -2.0 };
double[][] yDot = { { 1.0, 2.0, -2.0 } };
EulerStepInterpolator interpolator = new EulerStepInterpolator();
interpolator.reinitialize(new DummyIntegrator(interpolator), y, yDot, true,
new EquationsMapper(0, y.length),
new EquationsMapper[0]);
interpolator.storeTime(0);
interpolator.shift();
y[0] = 1.0;
y[1] = 3.0;
y[2] = -4.0;
interpolator.storeTime(1);
interpolator.setInterpolatedTime(0.1);
double[] result = interpolator.getInterpolatedState();
Assert.assertTrue(FastMath.abs(result[0] - 0.1) < 1.0e-10);
Assert.assertTrue(FastMath.abs(result[1] - 1.2) < 1.0e-10);
Assert.assertTrue(FastMath.abs(result[2] + 2.2) < 1.0e-10);
interpolator.setInterpolatedTime(0.5);
result = interpolator.getInterpolatedState();
Assert.assertTrue(FastMath.abs(result[0] - 0.5) < 1.0e-10);
Assert.assertTrue(FastMath.abs(result[1] - 2.0) < 1.0e-10);
Assert.assertTrue(FastMath.abs(result[2] + 3.0) < 1.0e-10);
}
@Test
public void derivativesConsistency()
throws DimensionMismatchException, NumberIsTooSmallException,
MaxCountExceededException, NoBracketingException {
TestProblem3 pb = new TestProblem3();
double step = (pb.getFinalTime() - pb.getInitialTime()) * 0.001;
EulerIntegrator integ = new EulerIntegrator(step);
StepInterpolatorTestUtils.checkDerivativesConsistency(integ, pb, 1.0e-10);
}
@Test
public void serialization()
throws IOException, ClassNotFoundException,
DimensionMismatchException, NumberIsTooSmallException,
MaxCountExceededException, NoBracketingException {
TestProblem1 pb = new TestProblem1();
double step = (pb.getFinalTime() - pb.getInitialTime()) * 0.001;
EulerIntegrator integ = new EulerIntegrator(step);
integ.addStepHandler(new ContinuousOutputModel());
integ.integrate(pb,
pb.getInitialTime(), pb.getInitialState(),
pb.getFinalTime(), new double[pb.getDimension()]);
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(bos);
for (StepHandler handler : integ.getStepHandlers()) {
oos.writeObject(handler);
}
ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
ObjectInputStream ois = new ObjectInputStream(bis);
ContinuousOutputModel cm = (ContinuousOutputModel) ois.readObject();
Random random = new Random(347588535632l);
double maxError = 0.0;
for (int i = 0; i < 1000; ++i) {
double r = random.nextDouble();
double time = r * pb.getInitialTime() + (1.0 - r) * pb.getFinalTime();
cm.setInterpolatedTime(time);
double[] interpolatedY = cm.getInterpolatedState ();
double[] theoreticalY = pb.computeTheoreticalState(time);
double dx = interpolatedY[0] - theoreticalY[0];
double dy = interpolatedY[1] - theoreticalY[1];
double error = dx * dx + dy * dy;
if (error > maxError) {
maxError = error;
}
}
Assert.assertTrue(maxError < 0.001);
}
private static class DummyIntegrator extends RungeKuttaIntegrator {
protected DummyIntegrator(RungeKuttaStepInterpolator prototype) {
super("dummy", new double[0], new double[0][0], new double[0], prototype, Double.NaN);
}
}
}