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.math3.ode;
019    
020    import org.apache.commons.math3.exception.DimensionMismatchException;
021    import org.apache.commons.math3.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     * @version $Id: FirstOrderDifferentialEquations.java 1416643 2012-12-03 19:37:14Z tn $
049     * @since 1.2
050     */
051    
052    public interface FirstOrderDifferentialEquations {
053    
054        /** Get the dimension of the problem.
055         * @return dimension of the problem
056         */
057        int getDimension();
058    
059        /** Get the current time derivative of the state vector.
060         * @param t current value of the independent <I>time</I> variable
061         * @param y array containing the current value of the state vector
062         * @param yDot placeholder array where to put the time derivative of the state vector
063         * @exception MaxCountExceededException if the number of functions evaluations is exceeded
064         * @exception DimensionMismatchException if arrays dimensions do not match equations settings
065         */
066        void computeDerivatives(double t, double[] y, double[] yDot)
067            throws MaxCountExceededException, DimensionMismatchException;
068    
069    }