| /* |
| * 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; |
| |
| import java.lang.reflect.Array; |
| |
| import org.apache.commons.math3.Field; |
| import org.apache.commons.math3.RealFieldElement; |
| import org.apache.commons.math3.ode.events.Action; |
| import org.apache.commons.math3.ode.events.FieldEventHandler; |
| import org.apache.commons.math3.util.FastMath; |
| import org.apache.commons.math3.util.MathArrays; |
| |
| /** |
| * This class is used in the junit tests for the ODE integrators. |
| |
| * <p>This specific problem is the following differential equation : |
| * <pre> |
| * x'' = -x |
| * </pre> |
| * And when x decreases down to 0, the state should be changed as follows : |
| * <pre> |
| * x' -> -x' |
| * </pre> |
| * The theoretical solution of this problem is x = |sin(t+a)| |
| * </p> |
| |
| * @param <T> the type of the field elements |
| */ |
| public class TestFieldProblem4<T extends RealFieldElement<T>> |
| extends TestFieldProblemAbstract<T> { |
| |
| /** Time offset. */ |
| private T a; |
| |
| /** Simple constructor. |
| * @param field field to which elements belong |
| */ |
| public TestFieldProblem4(Field<T> field) { |
| super(field); |
| a = convert(1.2); |
| T[] y0 = MathArrays.buildArray(field, 2); |
| y0[0] = a.sin(); |
| y0[1] = a.cos();; |
| setInitialConditions(convert(0.0), y0); |
| setFinalConditions(convert(15)); |
| setErrorScale(convert(1.0, 0.0)); |
| } |
| |
| @Override |
| public FieldEventHandler<T>[] getEventsHandlers() { |
| @SuppressWarnings("unchecked") |
| FieldEventHandler<T>[] handlers = |
| (FieldEventHandler<T>[]) Array.newInstance(FieldEventHandler.class, 2); |
| handlers[0] = new Bounce<T>(); |
| handlers[1] = new Stop<T>(); |
| return handlers; |
| } |
| |
| /** |
| * Get the theoretical events times. |
| * @return theoretical events times |
| */ |
| @Override |
| public T[] getTheoreticalEventsTimes() { |
| T[] array = MathArrays.buildArray(getField(), 5); |
| array[0] = a.negate().add(1 * FastMath.PI); |
| array[1] = a.negate().add(2 * FastMath.PI); |
| array[2] = a.negate().add(3 * FastMath.PI); |
| array[3] = a.negate().add(4 * FastMath.PI); |
| array[4] = convert(120.0); |
| return array; |
| } |
| |
| @Override |
| public T[] doComputeDerivatives(T t, T[] y) { |
| final T[] yDot = MathArrays.buildArray(getField(), getDimension()); |
| yDot[0] = y[1]; |
| yDot[1] = y[0].negate(); |
| return yDot; |
| } |
| |
| @Override |
| public T[] computeTheoreticalState(T t) { |
| T sin = t.add(a).sin(); |
| T cos = t.add(a).cos(); |
| final T[] y = MathArrays.buildArray(getField(), getDimension()); |
| y[0] = sin.abs(); |
| y[1] = (sin.getReal() >= 0) ? cos : cos.negate(); |
| return y; |
| } |
| |
| private static class Bounce<T extends RealFieldElement<T>> implements FieldEventHandler<T> { |
| |
| private int sign; |
| |
| public Bounce() { |
| sign = +1; |
| } |
| |
| public void init(FieldODEStateAndDerivative<T> state0, T t) { |
| } |
| |
| public T g(FieldODEStateAndDerivative<T> state) { |
| return state.getState()[0].multiply(sign); |
| } |
| |
| public Action eventOccurred(FieldODEStateAndDerivative<T> state, boolean increasing) { |
| // this sign change is needed because the state will be reset soon |
| sign = -sign; |
| return Action.RESET_STATE; |
| } |
| |
| public FieldODEState<T> resetState(FieldODEStateAndDerivative<T> state) { |
| T[] y = state.getState(); |
| y[0] = y[0].negate(); |
| y[1] = y[1].negate(); |
| return new FieldODEState<T>(state.getTime(), y); |
| } |
| |
| } |
| |
| private static class Stop<T extends RealFieldElement<T>> implements FieldEventHandler<T> { |
| |
| public Stop() { |
| } |
| |
| public void init(FieldODEStateAndDerivative<T> state0, T t) { |
| } |
| |
| public T g(FieldODEStateAndDerivative<T> state) { |
| return state.getTime().subtract(12.0); |
| } |
| |
| public Action eventOccurred(FieldODEStateAndDerivative<T> state, boolean increasing) { |
| return Action.STOP; |
| } |
| |
| public FieldODEState<T> resetState(FieldODEStateAndDerivative<T> state) { |
| return state; |
| } |
| |
| } |
| |
| } |