    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    }