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18 package org.apache.commons.math.ode.nonstiff;
19
20 import junit.framework.*;
21
22 import org.apache.commons.math.ode.DerivativeException;
23 import org.apache.commons.math.ode.FirstOrderDifferentialEquations;
24 import org.apache.commons.math.ode.FirstOrderIntegrator;
25 import org.apache.commons.math.ode.IntegratorException;
26 import org.apache.commons.math.ode.TestProblem1;
27 import org.apache.commons.math.ode.TestProblem5;
28 import org.apache.commons.math.ode.TestProblemAbstract;
29 import org.apache.commons.math.ode.TestProblemFactory;
30 import org.apache.commons.math.ode.TestProblemHandler;
31 import org.apache.commons.math.ode.events.EventHandler;
32 import org.apache.commons.math.ode.nonstiff.MidpointIntegrator;
33 import org.apache.commons.math.ode.sampling.StepHandler;
34 import org.apache.commons.math.ode.sampling.StepInterpolator;
35
36 public class MidpointIntegratorTest
37 extends TestCase {
38
39 public MidpointIntegratorTest(String name) {
40 super(name);
41 }
42
43 public void testDimensionCheck() {
44 try {
45 TestProblem1 pb = new TestProblem1();
46 new MidpointIntegrator(0.01).integrate(pb,
47 0.0, new double[pb.getDimension()+10],
48 1.0, new double[pb.getDimension()+10]);
49 fail("an exception should have been thrown");
50 } catch(DerivativeException de) {
51 fail("wrong exception caught");
52 } catch(IntegratorException ie) {
53 }
54 }
55
56 public void testDecreasingSteps()
57 throws DerivativeException, IntegratorException {
58
59 TestProblemAbstract[] problems = TestProblemFactory.getProblems();
60 for (int k = 0; k < problems.length; ++k) {
61
62 double previousError = Double.NaN;
63 for (int i = 4; i < 10; ++i) {
64
65 TestProblemAbstract pb = problems[k].copy();
66 double step = (pb.getFinalTime() - pb.getInitialTime())
67 * Math.pow(2.0, -i);
68 FirstOrderIntegrator integ = new MidpointIntegrator(step);
69 TestProblemHandler handler = new TestProblemHandler(pb, integ);
70 integ.addStepHandler(handler);
71 EventHandler[] functions = pb.getEventsHandlers();
72 for (int l = 0; l < functions.length; ++l) {
73 integ.addEventHandler(functions[l],
74 Double.POSITIVE_INFINITY, 1.0e-6 * step, 1000);
75 }
76 double stopTime = integ.integrate(pb,
77 pb.getInitialTime(), pb.getInitialState(),
78 pb.getFinalTime(), new double[pb.getDimension()]);
79 if (functions.length == 0) {
80 assertEquals(pb.getFinalTime(), stopTime, 1.0e-10);
81 }
82
83 double error = handler.getMaximalValueError();
84 if (i > 4) {
85 assertTrue(error < Math.abs(previousError));
86 }
87 previousError = error;
88 assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);
89
90 }
91
92 }
93
94 }
95
96 public void testSmallStep()
97 throws DerivativeException, IntegratorException {
98
99 TestProblem1 pb = new TestProblem1();
100 double step = (pb.getFinalTime() - pb.getInitialTime()) * 0.001;
101
102 FirstOrderIntegrator integ = new MidpointIntegrator(step);
103 TestProblemHandler handler = new TestProblemHandler(pb, integ);
104 integ.addStepHandler(handler);
105 integ.integrate(pb,
106 pb.getInitialTime(), pb.getInitialState(),
107 pb.getFinalTime(), new double[pb.getDimension()]);
108
109 assertTrue(handler.getLastError() < 2.0e-7);
110 assertTrue(handler.getMaximalValueError() < 1.0e-6);
111 assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);
112 assertEquals("midpoint", integ.getName());
113
114 }
115
116 public void testBigStep()
117 throws DerivativeException, IntegratorException {
118
119 TestProblem1 pb = new TestProblem1();
120 double step = (pb.getFinalTime() - pb.getInitialTime()) * 0.2;
121
122 FirstOrderIntegrator integ = new MidpointIntegrator(step);
123 TestProblemHandler handler = new TestProblemHandler(pb, integ);
124 integ.addStepHandler(handler);
125 integ.integrate(pb,
126 pb.getInitialTime(), pb.getInitialState(),
127 pb.getFinalTime(), new double[pb.getDimension()]);
128
129 assertTrue(handler.getLastError() > 0.01);
130 assertTrue(handler.getMaximalValueError() > 0.05);
131 assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);
132
133 }
134
135 public void testBackward()
136 throws DerivativeException, IntegratorException {
137
138 TestProblem5 pb = new TestProblem5();
139 double step = Math.abs(pb.getFinalTime() - pb.getInitialTime()) * 0.001;
140
141 FirstOrderIntegrator integ = new MidpointIntegrator(step);
142 TestProblemHandler handler = new TestProblemHandler(pb, integ);
143 integ.addStepHandler(handler);
144 integ.integrate(pb, pb.getInitialTime(), pb.getInitialState(),
145 pb.getFinalTime(), new double[pb.getDimension()]);
146
147 assertTrue(handler.getLastError() < 6.0e-4);
148 assertTrue(handler.getMaximalValueError() < 6.0e-4);
149 assertEquals(0, handler.getMaximalTimeError(), 1.0e-12);
150 assertEquals("midpoint", integ.getName());
151 }
152
153 public void testStepSize()
154 throws DerivativeException, IntegratorException {
155 final double step = 1.23456;
156 FirstOrderIntegrator integ = new MidpointIntegrator(step);
157 integ.addStepHandler(new StepHandler() {
158 public void handleStep(StepInterpolator interpolator, boolean isLast) {
159 if (! isLast) {
160 assertEquals(step,
161 interpolator.getCurrentTime() - interpolator.getPreviousTime(),
162 1.0e-12);
163 }
164 }
165 public boolean requiresDenseOutput() {
166 return false;
167 }
168 public void reset() {
169 }
170 });
171 integ.integrate(new FirstOrderDifferentialEquations() {
172 private static final long serialVersionUID = 0L;
173 public void computeDerivatives(double t, double[] y, double[] dot) {
174 dot[0] = 1.0;
175 }
176 public int getDimension() {
177 return 1;
178 }
179 }, 0.0, new double[] { 0.0 }, 5.0, new double[1]);
180 }
181
182 public static Test suite() {
183 return new TestSuite(MidpointIntegratorTest.class);
184 }
185
186 }