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 /** This interface represents a second order differential equations set.
021
022 * <p>This interface should be implemented by all real second order
023 * differential equation problems before they can be handled by the
024 * integrators {@link SecondOrderIntegrator#integrate} method.</p>
025 *
026 * <p>A second order differential equations problem, as seen by an
027 * integrator is the second time derivative <code>d2Y/dt^2</code> of a
028 * state vector <code>Y</code>, both being one dimensional
029 * arrays. From the integrator point of view, this derivative depends
030 * only on the current time <code>t</code>, on the state vector
031 * <code>Y</code> and on the first time derivative of the state
032 * vector.</p>
033 *
034 * <p>For real problems, the derivative depends also on parameters
035 * that do not belong to the state vector (dynamical model constants
036 * for example). These constants are completely outside of the scope
037 * of this interface, the classes that implement it are allowed to
038 * handle them as they want.</p>
039 *
040 * @see SecondOrderIntegrator
041 * @see FirstOrderConverter
042 * @see FirstOrderDifferentialEquations
043 * @version $Revision: 811786 $ $Date: 2009-09-06 05:36:08 -0400 (Sun, 06 Sep 2009) $
044 * @since 1.2
045 */
046
047 public interface SecondOrderDifferentialEquations {
048
049 /** Get the dimension of the problem.
050 * @return dimension of the problem
051 */
052 int getDimension();
053
054 /** Get the current time derivative of the state vector.
055 * @param t current value of the independent <I>time</I> variable
056 * @param y array containing the current value of the state vector
057 * @param yDot array containing the current value of the first derivative
058 * of the state vector
059 * @param yDDot placeholder array where to put the second time derivative
060 * of the state vector
061 * @throws DerivativeException this exception is propagated to the caller if the
062 * underlying user function triggers one
063 */
064 void computeSecondDerivatives(double t, double[] y, double[] yDot,
065 double[] yDDot) throws DerivativeException;
066
067 }