001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018 package org.apache.commons.math.ode;
019
020 import org.apache.commons.math.ode.DerivativeException;
021
022 /** This interface represents a second order differential equations set.
023
024 * <p>This interface should be implemented by all real second order
025 * differential equation problems before they can be handled by the
026 * integrators {@link SecondOrderIntegrator#integrate} method.</p>
027 *
028 * <p>A second order differential equations problem, as seen by an
029 * integrator is the second time derivative <code>d2Y/dt^2</code> of a
030 * state vector <code>Y</code>, both being one dimensional
031 * arrays. From the integrator point of view, this derivative depends
032 * only on the current time <code>t</code>, on the state vector
033 * <code>Y</code> and on the first time derivative of the state
034 * vector.</p>
035 *
036 * <p>For real problems, the derivative depends also on parameters
037 * that do not belong to the state vector (dynamical model constants
038 * for example). These constants are completely outside of the scope
039 * of this interface, the classes that implement it are allowed to
040 * handle them as they want.</p>
041 *
042 * @see SecondOrderIntegrator
043 * @see FirstOrderConverter
044 * @see FirstOrderDifferentialEquations
045 * @version $Revision: 1073158 $ $Date: 2011-02-21 22:46:52 +0100 (lun. 21 f??vr. 2011) $
046 * @since 1.2
047 */
048
049 public interface SecondOrderDifferentialEquations {
050
051 /** Get the dimension of the problem.
052 * @return dimension of the problem
053 */
054 int getDimension();
055
056 /** Get the current time derivative of the state vector.
057 * @param t current value of the independent <I>time</I> variable
058 * @param y array containing the current value of the state vector
059 * @param yDot array containing the current value of the first derivative
060 * of the state vector
061 * @param yDDot placeholder array where to put the second time derivative
062 * of the state vector
063 * @throws DerivativeException this user-defined exception should be used if an error is
064 * is triggered by user code
065 */
066 void computeSecondDerivatives(double t, double[] y, double[] yDot, double[] yDDot)
067 throws DerivativeException;
068
069 }