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Java example source code file (RungeKuttaFieldIntegratorAbstractTest.java)
This example Java source code file (RungeKuttaFieldIntegratorAbstractTest.java) is included in the alvinalexander.com
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The RungeKuttaFieldIntegratorAbstractTest.java Java example source code
/*
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* 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
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*
* http://www.apache.org/licenses/LICENSE-2.0
*
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* distributed under the License is distributed on an "AS IS" BASIS,
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package org.apache.commons.math3.ode.nonstiff;
import java.lang.reflect.Array;
import org.apache.commons.math3.Field;
import org.apache.commons.math3.RealFieldElement;
import org.apache.commons.math3.analysis.differentiation.DerivativeStructure;
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.FirstOrderFieldDifferentialEquations;
import org.apache.commons.math3.ode.FieldODEState;
import org.apache.commons.math3.ode.FieldODEStateAndDerivative;
import org.apache.commons.math3.ode.TestFieldProblem1;
import org.apache.commons.math3.ode.TestFieldProblem2;
import org.apache.commons.math3.ode.TestFieldProblem3;
import org.apache.commons.math3.ode.TestFieldProblem4;
import org.apache.commons.math3.ode.TestFieldProblem5;
import org.apache.commons.math3.ode.TestFieldProblem6;
import org.apache.commons.math3.ode.TestFieldProblemAbstract;
import org.apache.commons.math3.ode.TestFieldProblemHandler;
import org.apache.commons.math3.ode.events.Action;
import org.apache.commons.math3.ode.events.FieldEventHandler;
import org.apache.commons.math3.ode.sampling.FieldStepHandler;
import org.apache.commons.math3.ode.sampling.FieldStepInterpolator;
import org.apache.commons.math3.ode.sampling.StepInterpolatorTestUtils;
import org.apache.commons.math3.util.FastMath;
import org.apache.commons.math3.util.MathArrays;
import org.junit.Assert;
import org.junit.Test;
public abstract class RungeKuttaFieldIntegratorAbstractTest {
protected abstract <T extends RealFieldElement RungeKuttaFieldIntegrator
createIntegrator(Field<T> field, T step);
@Test
public abstract void testNonFieldIntegratorConsistency();
protected <T extends RealFieldElement void doTestNonFieldIntegratorConsistency(final Field field) {
try {
// get the Butcher arrays from the field integrator
RungeKuttaFieldIntegrator<T> fieldIntegrator = createIntegrator(field, field.getZero().add(1));
T[][] fieldA = fieldIntegrator.getA();
T[] fieldB = fieldIntegrator.getB();
T[] fieldC = fieldIntegrator.getC();
String fieldName = fieldIntegrator.getClass().getName();
String regularName = fieldName.replaceAll("Field", "");
// get the Butcher arrays from the regular integrator
@SuppressWarnings("unchecked")
Class<RungeKuttaIntegrator> c = (Class) Class.forName(regularName);
java.lang.reflect.Field jlrFieldA = c.getDeclaredField("STATIC_A");
jlrFieldA.setAccessible(true);
double[][] regularA = (double[][]) jlrFieldA.get(null);
java.lang.reflect.Field jlrFieldB = c.getDeclaredField("STATIC_B");
jlrFieldB.setAccessible(true);
double[] regularB = (double[]) jlrFieldB.get(null);
java.lang.reflect.Field jlrFieldC = c.getDeclaredField("STATIC_C");
jlrFieldC.setAccessible(true);
double[] regularC = (double[]) jlrFieldC.get(null);
Assert.assertEquals(regularA.length, fieldA.length);
for (int i = 0; i < regularA.length; ++i) {
checkArray(regularA[i], fieldA[i]);
}
checkArray(regularB, fieldB);
checkArray(regularC, fieldC);
} catch (ClassNotFoundException cnfe) {
Assert.fail(cnfe.getLocalizedMessage());
} catch (IllegalAccessException iae) {
Assert.fail(iae.getLocalizedMessage());
} catch (IllegalArgumentException iae) {
Assert.fail(iae.getLocalizedMessage());
} catch (SecurityException se) {
Assert.fail(se.getLocalizedMessage());
} catch (NoSuchFieldException nsfe) {
Assert.fail(nsfe.getLocalizedMessage());
}
}
private <T extends RealFieldElement void checkArray(double[] regularArray, T[] fieldArray) {
Assert.assertEquals(regularArray.length, fieldArray.length);
for (int i = 0; i < regularArray.length; ++i) {
if (regularArray[i] == 0) {
Assert.assertTrue(0.0 == fieldArray[i].getReal());
} else {
Assert.assertEquals(regularArray[i], fieldArray[i].getReal(), FastMath.ulp(regularArray[i]));
}
}
}
@Test
public abstract void testMissedEndEvent();
protected <T extends RealFieldElement void doTestMissedEndEvent(final Field field,
final double epsilonT, final double epsilonY)
throws DimensionMismatchException, NumberIsTooSmallException,
MaxCountExceededException, NoBracketingException {
final T t0 = field.getZero().add(1878250320.0000029);
final T tEvent = field.getZero().add(1878250379.9999986);
final T[] k = MathArrays.buildArray(field, 3);
k[0] = field.getZero().add(1.0e-4);
k[1] = field.getZero().add(1.0e-5);
k[2] = field.getZero().add(1.0e-6);
FirstOrderFieldDifferentialEquations<T> ode = new FirstOrderFieldDifferentialEquations() {
public int getDimension() {
return k.length;
}
public void init(T t0, T[] y0, T t) {
}
public T[] computeDerivatives(T t, T[] y) {
T[] yDot = MathArrays.buildArray(field, k.length);
for (int i = 0; i < y.length; ++i) {
yDot[i] = k[i].multiply(y[i]);
}
return yDot;
}
};
RungeKuttaFieldIntegrator<T> integrator = createIntegrator(field, field.getZero().add(60.0));
T[] y0 = MathArrays.buildArray(field, k.length);
for (int i = 0; i < y0.length; ++i) {
y0[i] = field.getOne().add(i);
}
FieldODEStateAndDerivative<T> result = integrator.integrate(new FieldExpandableODE(ode),
new FieldODEState<T>(t0, y0),
tEvent);
Assert.assertEquals(tEvent.getReal(), result.getTime().getReal(), epsilonT);
T[] y = result.getState();
for (int i = 0; i < y.length; ++i) {
Assert.assertEquals(y0[i].multiply(k[i].multiply(result.getTime().subtract(t0)).exp()).getReal(),
y[i].getReal(),
epsilonY);
}
integrator.addEventHandler(new FieldEventHandler<T>() {
public void init(FieldODEStateAndDerivative<T> state0, T t) {
}
public FieldODEState<T> resetState(FieldODEStateAndDerivative state) {
return state;
}
public T g(FieldODEStateAndDerivative<T> state) {
return state.getTime().subtract(tEvent);
}
public Action eventOccurred(FieldODEStateAndDerivative<T> state, boolean increasing) {
Assert.assertEquals(tEvent.getReal(), state.getTime().getReal(), epsilonT);
return Action.CONTINUE;
}
}, Double.POSITIVE_INFINITY, 1.0e-20, 100);
result = integrator.integrate(new FieldExpandableODE<T>(ode),
new FieldODEState<T>(t0, y0),
tEvent.add(120));
Assert.assertEquals(tEvent.add(120).getReal(), result.getTime().getReal(), epsilonT);
y = result.getState();
for (int i = 0; i < y.length; ++i) {
Assert.assertEquals(y0[i].multiply(k[i].multiply(result.getTime().subtract(t0)).exp()).getReal(),
y[i].getReal(),
epsilonY);
}
}
@Test
public abstract void testSanityChecks();
protected <T extends RealFieldElement void doTestSanityChecks(Field field)
throws DimensionMismatchException, NumberIsTooSmallException,
MaxCountExceededException, NoBracketingException {
RungeKuttaFieldIntegrator<T> integrator = createIntegrator(field, field.getZero().add(0.01));
try {
TestFieldProblem1<T> pb = new TestFieldProblem1(field);
integrator.integrate(new FieldExpandableODE<T>(pb),
new FieldODEState<T>(field.getZero(), MathArrays.buildArray(field, pb.getDimension() + 10)),
field.getOne());
Assert.fail("an exception should have been thrown");
} catch(DimensionMismatchException ie) {
}
try {
TestFieldProblem1<T> pb = new TestFieldProblem1(field);
integrator.integrate(new FieldExpandableODE<T>(pb),
new FieldODEState<T>(field.getZero(), MathArrays.buildArray(field, pb.getDimension())),
field.getZero());
Assert.fail("an exception should have been thrown");
} catch(NumberIsTooSmallException ie) {
}
}
@Test
public abstract void testDecreasingSteps();
protected <T extends RealFieldElement void doTestDecreasingSteps(Field field,
final double safetyValueFactor,
final double safetyTimeFactor,
final double epsilonT)
throws DimensionMismatchException, NumberIsTooSmallException,
MaxCountExceededException, NoBracketingException {
@SuppressWarnings("unchecked")
TestFieldProblemAbstract<T>[] allProblems =
(TestFieldProblemAbstract<T>[]) Array.newInstance(TestFieldProblemAbstract.class, 6);
allProblems[0] = new TestFieldProblem1<T>(field);
allProblems[1] = new TestFieldProblem2<T>(field);
allProblems[2] = new TestFieldProblem3<T>(field);
allProblems[3] = new TestFieldProblem4<T>(field);
allProblems[4] = new TestFieldProblem5<T>(field);
allProblems[5] = new TestFieldProblem6<T>(field);
for (TestFieldProblemAbstract<T> pb : allProblems) {
T previousValueError = null;
T previousTimeError = null;
for (int i = 4; i < 10; ++i) {
T step = pb.getFinalTime().subtract(pb.getInitialState().getTime()).multiply(FastMath.pow(2.0, -i));
RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, step);
TestFieldProblemHandler<T> handler = new TestFieldProblemHandler(pb, integ);
integ.addStepHandler(handler);
FieldEventHandler<T>[] functions = pb.getEventsHandlers();
for (int l = 0; l < functions.length; ++l) {
integ.addEventHandler(functions[l],
Double.POSITIVE_INFINITY, 1.0e-6 * step.getReal(), 1000);
}
Assert.assertEquals(functions.length, integ.getEventHandlers().size());
FieldODEStateAndDerivative<T> stop = integ.integrate(new FieldExpandableODE(pb),
pb.getInitialState(),
pb.getFinalTime());
if (functions.length == 0) {
Assert.assertEquals(pb.getFinalTime().getReal(), stop.getTime().getReal(), epsilonT);
}
T error = handler.getMaximalValueError();
if (i > 4) {
Assert.assertTrue(error.subtract(previousValueError.abs().multiply(safetyValueFactor)).getReal() < 0);
}
previousValueError = error;
T timeError = handler.getMaximalTimeError();
if (i > 4) {
Assert.assertTrue(timeError.subtract(previousTimeError.abs().multiply(safetyTimeFactor)).getReal() <= 0);
}
previousTimeError = timeError;
integ.clearEventHandlers();
Assert.assertEquals(0, integ.getEventHandlers().size());
}
}
}
@Test
public abstract void testSmallStep();
protected <T extends RealFieldElement void doTestSmallStep(Field field,
final double epsilonLast,
final double epsilonMaxValue,
final double epsilonMaxTime,
final String name)
throws DimensionMismatchException, NumberIsTooSmallException,
MaxCountExceededException, NoBracketingException {
TestFieldProblem1<T> pb = new TestFieldProblem1(field);
T step = pb.getFinalTime().subtract(pb.getInitialState().getTime()).multiply(0.001);
RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, step);
TestFieldProblemHandler<T> handler = new TestFieldProblemHandler(pb, integ);
integ.addStepHandler(handler);
integ.integrate(new FieldExpandableODE<T>(pb), pb.getInitialState(), pb.getFinalTime());
Assert.assertEquals(0, handler.getLastError().getReal(), epsilonLast);
Assert.assertEquals(0, handler.getMaximalValueError().getReal(), epsilonMaxValue);
Assert.assertEquals(0, handler.getMaximalTimeError().getReal(), epsilonMaxTime);
Assert.assertEquals(name, integ.getName());
}
@Test
public abstract void testBigStep();
protected <T extends RealFieldElement void doTestBigStep(Field field,
final double belowLast,
final double belowMaxValue,
final double epsilonMaxTime,
final String name)
throws DimensionMismatchException, NumberIsTooSmallException,
MaxCountExceededException, NoBracketingException {
TestFieldProblem1<T> pb = new TestFieldProblem1(field);
T step = pb.getFinalTime().subtract(pb.getInitialState().getTime()).multiply(0.2);
RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, step);
TestFieldProblemHandler<T> handler = new TestFieldProblemHandler(pb, integ);
integ.addStepHandler(handler);
integ.integrate(new FieldExpandableODE<T>(pb), pb.getInitialState(), pb.getFinalTime());
Assert.assertTrue(handler.getLastError().getReal() > belowLast);
Assert.assertTrue(handler.getMaximalValueError().getReal() > belowMaxValue);
Assert.assertEquals(0, handler.getMaximalTimeError().getReal(), epsilonMaxTime);
Assert.assertEquals(name, integ.getName());
}
@Test
public abstract void testBackward();
protected <T extends RealFieldElement void doTestBackward(Field field,
final double epsilonLast,
final double epsilonMaxValue,
final double epsilonMaxTime,
final String name)
throws DimensionMismatchException, NumberIsTooSmallException,
MaxCountExceededException, NoBracketingException {
TestFieldProblem5<T> pb = new TestFieldProblem5(field);
T step = pb.getFinalTime().subtract(pb.getInitialState().getTime()).multiply(0.001).abs();
RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, step);
TestFieldProblemHandler<T> handler = new TestFieldProblemHandler(pb, integ);
integ.addStepHandler(handler);
integ.integrate(new FieldExpandableODE<T>(pb), pb.getInitialState(), pb.getFinalTime());
Assert.assertEquals(0, handler.getLastError().getReal(), epsilonLast);
Assert.assertEquals(0, handler.getMaximalValueError().getReal(), epsilonMaxValue);
Assert.assertEquals(0, handler.getMaximalTimeError().getReal(), epsilonMaxTime);
Assert.assertEquals(name, integ.getName());
}
@Test
public abstract void testKepler();
protected <T extends RealFieldElement void doTestKepler(Field field, double expectedMaxError, double epsilon)
throws DimensionMismatchException, NumberIsTooSmallException,
MaxCountExceededException, NoBracketingException {
final TestFieldProblem3<T> pb = new TestFieldProblem3(field, field.getZero().add(0.9));
T step = pb.getFinalTime().subtract(pb.getInitialState().getTime()).multiply(0.0003);
RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, step);
integ.addStepHandler(new KeplerHandler<T>(pb, expectedMaxError, epsilon));
integ.integrate(new FieldExpandableODE<T>(pb), pb.getInitialState(), pb.getFinalTime());
}
private static class KeplerHandler<T extends RealFieldElement implements FieldStepHandler {
private T maxError;
private final TestFieldProblem3<T> pb;
private final double expectedMaxError;
private final double epsilon;
public KeplerHandler(TestFieldProblem3<T> pb, double expectedMaxError, double epsilon) {
this.pb = pb;
this.expectedMaxError = expectedMaxError;
this.epsilon = epsilon;
maxError = pb.getField().getZero();
}
public void init(FieldODEStateAndDerivative<T> state0, T t) {
maxError = pb.getField().getZero();
}
public void handleStep(FieldStepInterpolator<T> interpolator, boolean isLast)
throws MaxCountExceededException {
FieldODEStateAndDerivative<T> current = interpolator.getCurrentState();
T[] theoreticalY = pb.computeTheoreticalState(current.getTime());
T dx = current.getState()[0].subtract(theoreticalY[0]);
T dy = current.getState()[1].subtract(theoreticalY[1]);
T error = dx.multiply(dx).add(dy.multiply(dy));
if (error.subtract(maxError).getReal() > 0) {
maxError = error;
}
if (isLast) {
Assert.assertEquals(expectedMaxError, maxError.getReal(), epsilon);
}
}
}
@Test
public abstract void testStepSize();
protected <T extends RealFieldElement void doTestStepSize(final Field field, final double epsilon)
throws DimensionMismatchException, NumberIsTooSmallException,
MaxCountExceededException, NoBracketingException {
final T step = field.getZero().add(1.23456);
RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, step);
integ.addStepHandler(new FieldStepHandler<T>() {
public void handleStep(FieldStepInterpolator<T> interpolator, boolean isLast) {
if (! isLast) {
Assert.assertEquals(step.getReal(),
interpolator.getCurrentState().getTime().subtract(interpolator.getPreviousState().getTime()).getReal(),
epsilon);
}
}
public void init(FieldODEStateAndDerivative<T> s0, T t) {
}
});
integ.integrate(new FieldExpandableODE<T>(new FirstOrderFieldDifferentialEquations() {
public void init(T t0, T[] y0, T t) {
}
public T[] computeDerivatives(T t, T[] y) {
T[] dot = MathArrays.buildArray(t.getField(), 1);
dot[0] = t.getField().getOne();
return dot;
}
public int getDimension() {
return 1;
}
}), new FieldODEState<T>(field.getZero(), MathArrays.buildArray(field, 1)), field.getZero().add(5.0));
}
@Test
public abstract void testSingleStep();
protected <T extends RealFieldElement void doTestSingleStep(final Field field, final double epsilon) {
final TestFieldProblem3<T> pb = new TestFieldProblem3(field, field.getZero().add(0.9));
T h = pb.getFinalTime().subtract(pb.getInitialState().getTime()).multiply(0.0003);
RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, field.getZero().add(Double.NaN));
T t = pb.getInitialState().getTime();
T[] y = pb.getInitialState().getState();
for (int i = 0; i < 100; ++i) {
y = integ.singleStep(pb, t, y, t.add(h));
t = t.add(h);
}
T[] yth = pb.computeTheoreticalState(t);
T dx = y[0].subtract(yth[0]);
T dy = y[1].subtract(yth[1]);
T error = dx.multiply(dx).add(dy.multiply(dy));
Assert.assertEquals(0.0, error.getReal(), epsilon);
}
@Test
public abstract void testTooLargeFirstStep();
protected <T extends RealFieldElement void doTestTooLargeFirstStep(final Field field) {
RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, field.getZero().add(0.5));
final T t0 = field.getZero();
final T[] y0 = MathArrays.buildArray(field, 1);
y0[0] = field.getOne();
final T t = field.getZero().add(0.001);
FirstOrderFieldDifferentialEquations<T> equations = new FirstOrderFieldDifferentialEquations() {
public int getDimension() {
return 1;
}
public void init(T t0, T[] y0, T t) {
}
public T[] computeDerivatives(T t, T[] y) {
Assert.assertTrue(t.getReal() >= FastMath.nextAfter(t0.getReal(), Double.NEGATIVE_INFINITY));
Assert.assertTrue(t.getReal() <= FastMath.nextAfter(t.getReal(), Double.POSITIVE_INFINITY));
T[] yDot = MathArrays.buildArray(field, 1);
yDot[0] = y[0].multiply(-100.0);
return yDot;
}
};
integ.integrate(new FieldExpandableODE<T>(equations), new FieldODEState(t0, y0), t);
}
@Test
public abstract void testUnstableDerivative();
protected <T extends RealFieldElement void doTestUnstableDerivative(Field field, double epsilon) {
final StepFieldProblem<T> stepProblem = new StepFieldProblem(field,
field.getZero().add(0.0),
field.getZero().add(1.0),
field.getZero().add(2.0));
RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, field.getZero().add(0.3));
integ.addEventHandler(stepProblem, 1.0, 1.0e-12, 1000);
FieldODEStateAndDerivative<T> result = integ.integrate(new FieldExpandableODE(stepProblem),
new FieldODEState<T>(field.getZero(), MathArrays.buildArray(field, 1)),
field.getZero().add(10.0));
Assert.assertEquals(8.0, result.getState()[0].getReal(), epsilon);
}
@Test
public abstract void testDerivativesConsistency();
protected <T extends RealFieldElement void doTestDerivativesConsistency(final Field field, double epsilon) {
TestFieldProblem3<T> pb = new TestFieldProblem3(field);
T step = pb.getFinalTime().subtract(pb.getInitialState().getTime()).multiply(0.001);
RungeKuttaFieldIntegrator<T> integ = createIntegrator(field, step);
StepInterpolatorTestUtils.checkDerivativesConsistency(integ, pb, 1.0e-10);
}
@Test
public abstract void testPartialDerivatives();
protected void doTestPartialDerivatives(final double epsilonY,
final double[] epsilonPartials) {
// parameters indices
final int parameters = 5;
final int order = 1;
final int parOmega = 0;
final int parTO = 1;
final int parY00 = 2;
final int parY01 = 3;
final int parT = 4;
DerivativeStructure omega = new DerivativeStructure(parameters, order, parOmega, 1.3);
DerivativeStructure t0 = new DerivativeStructure(parameters, order, parTO, 1.3);
DerivativeStructure[] y0 = new DerivativeStructure[] {
new DerivativeStructure(parameters, order, parY00, 3.0),
new DerivativeStructure(parameters, order, parY01, 4.0)
};
DerivativeStructure t = new DerivativeStructure(parameters, order, parT, 6.0);
SinCos sinCos = new SinCos(omega);
RungeKuttaFieldIntegrator<DerivativeStructure> integrator =
createIntegrator(omega.getField(), t.subtract(t0).multiply(0.001));
FieldODEStateAndDerivative<DerivativeStructure> result =
integrator.integrate(new FieldExpandableODE<DerivativeStructure>(sinCos),
new FieldODEState<DerivativeStructure>(t0, y0),
t);
// check values
for (int i = 0; i < sinCos.getDimension(); ++i) {
Assert.assertEquals(sinCos.theoreticalY(t.getReal())[i], result.getState()[i].getValue(), epsilonY);
}
// check derivatives
final double[][] derivatives = sinCos.getDerivatives(t.getReal());
for (int i = 0; i < sinCos.getDimension(); ++i) {
for (int parameter = 0; parameter < parameters; ++parameter) {
Assert.assertEquals(derivatives[i][parameter],
dYdP(result.getState()[i], parameter),
epsilonPartials[parameter]);
}
}
}
private double dYdP(final DerivativeStructure y, final int parameter) {
int[] orders = new int[y.getFreeParameters()];
orders[parameter] = 1;
return y.getPartialDerivative(orders);
}
private static class SinCos implements FirstOrderFieldDifferentialEquations<DerivativeStructure> {
private final DerivativeStructure omega;
private DerivativeStructure r;
private DerivativeStructure alpha;
private double dRdY00;
private double dRdY01;
private double dAlphadOmega;
private double dAlphadT0;
private double dAlphadY00;
private double dAlphadY01;
protected SinCos(final DerivativeStructure omega) {
this.omega = omega;
}
public int getDimension() {
return 2;
}
public void init(final DerivativeStructure t0, final DerivativeStructure[] y0,
final DerivativeStructure finalTime) {
// theoretical solution is y(t) = { r * sin(omega * t + alpha), r * cos(omega * t + alpha) }
// so we retrieve alpha by identification from the initial state
final DerivativeStructure r2 = y0[0].multiply(y0[0]).add(y0[1].multiply(y0[1]));
this.r = r2.sqrt();
this.dRdY00 = y0[0].divide(r).getReal();
this.dRdY01 = y0[1].divide(r).getReal();
this.alpha = y0[0].atan2(y0[1]).subtract(t0.multiply(omega));
this.dAlphadOmega = -t0.getReal();
this.dAlphadT0 = -omega.getReal();
this.dAlphadY00 = y0[1].divide(r2).getReal();
this.dAlphadY01 = y0[0].negate().divide(r2).getReal();
}
public DerivativeStructure[] computeDerivatives(final DerivativeStructure t, final DerivativeStructure[] y) {
return new DerivativeStructure[] {
omega.multiply(y[1]),
omega.multiply(y[0]).negate()
};
}
public double[] theoreticalY(final double t) {
final double theta = omega.getReal() * t + alpha.getReal();
return new double[] {
r.getReal() * FastMath.sin(theta), r.getReal() * FastMath.cos(theta)
};
}
public double[][] getDerivatives(final double t) {
// intermediate angle and state
final double theta = omega.getReal() * t + alpha.getReal();
final double sin = FastMath.sin(theta);
final double cos = FastMath.cos(theta);
final double y0 = r.getReal() * sin;
final double y1 = r.getReal() * cos;
// partial derivatives of the state first component
final double dY0dOmega = y1 * (t + dAlphadOmega);
final double dY0dT0 = y1 * dAlphadT0;
final double dY0dY00 = dRdY00 * sin + y1 * dAlphadY00;
final double dY0dY01 = dRdY01 * sin + y1 * dAlphadY01;
final double dY0dT = y1 * omega.getReal();
// partial derivatives of the state second component
final double dY1dOmega = - y0 * (t + dAlphadOmega);
final double dY1dT0 = - y0 * dAlphadT0;
final double dY1dY00 = dRdY00 * cos - y0 * dAlphadY00;
final double dY1dY01 = dRdY01 * cos - y0 * dAlphadY01;
final double dY1dT = - y0 * omega.getReal();
return new double[][] {
{ dY0dOmega, dY0dT0, dY0dY00, dY0dY01, dY0dT },
{ dY1dOmega, dY1dT0, dY1dY00, dY1dY01, dY1dT }
};
}
}
}
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