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
018package org.apache.commons.math4.ode;
019
020import org.apache.commons.math4.exception.DimensionMismatchException;
021import org.apache.commons.math4.exception.MaxCountExceededException;
022
023
024
025/** This interface represents a first order differential equations set.
026 *
027 * <p>This interface should be implemented by all real first order
028 * differential equation problems before they can be handled by the
029 * integrators {@link FirstOrderIntegrator#integrate} method.</p>
030 *
031 * <p>A first order differential equations problem, as seen by an
032 * integrator is the time derivative <code>dY/dt</code> of a state
033 * vector <code>Y</code>, both being one dimensional arrays. From the
034 * integrator point of view, this derivative depends only on the
035 * current time <code>t</code> and on the state vector
036 * <code>Y</code>.</p>
037 *
038 * <p>For real problems, the derivative depends also on parameters
039 * that do not belong to the state vector (dynamical model constants
040 * for example). These constants are completely outside of the scope
041 * of this interface, the classes that implement it are allowed to
042 * handle them as they want.</p>
043 *
044 * @see FirstOrderIntegrator
045 * @see FirstOrderConverter
046 * @see SecondOrderDifferentialEquations
047 *
048 * @since 1.2
049 */
050
051public interface FirstOrderDifferentialEquations {
052
053    /** Get the dimension of the problem.
054     * @return dimension of the problem
055     */
056    int getDimension();
057
058    /** Get the current time derivative of the state vector.
059     * @param t current value of the independent <I>time</I> variable
060     * @param y array containing the current value of the state vector
061     * @param yDot placeholder array where to put the time derivative of the state vector
062     * @exception MaxCountExceededException if the number of functions evaluations is exceeded
063     * @exception DimensionMismatchException if arrays dimensions do not match equations settings
064     */
065    void computeDerivatives(double t, double[] y, double[] yDot)
066        throws MaxCountExceededException, DimensionMismatchException;
067
068}