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/*
* 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;
/**
* This class is used in the junit tests for the ODE integrators.
* <p>This specific problem is the following differential equation :
* <pre>
* y' = 3x^5 - y
* </pre>
* when the initial condition is y(0) = -360, the solution of this
* equation degenerates to a simple quintic polynomial function :
* <pre>
* y (t) = 3x^5 - 15x^4 + 60x^3 - 180x^2 + 360x - 360
* </pre>
* </p>
*/
public class TestProblem6
extends TestProblemAbstract {
/** theoretical state */
private double[] y;
/**
* Simple constructor.
*/
public TestProblem6() {
super();
double[] y0 = { -360.0 };
setInitialConditions(0.0, y0);
setFinalConditions(1.0);
double[] errorScale = { 1.0 };
setErrorScale(errorScale);
y = new double[y0.length];
}
@Override
public void doComputeDerivatives(double t, double[] y, double[] yDot) {
// compute the derivatives
double t2 = t * t;
double t4 = t2 * t2;
double t5 = t4 * t;
for (int i = 0; i < getDimension(); ++i) {
yDot[i] = 3 * t5 - y[i];
}
}
@Override
public double[] computeTheoreticalState(double t) {
for (int i = 0; i < getDimension(); ++i) {
y[i] = ((((3 * t - 15) * t + 60) * t - 180) * t + 360) * t - 360;
}
return y;
}
}