    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
    021
    022    /** This interface represents a first order differential equations set.
    023     *
    024     * <p>This interface should be implemented by all real first order
    025     * differential equation problems before they can be handled by the
    026     * integrators {@link FirstOrderIntegrator#integrate} method.</p>
    027     *
    028     * <p>A first order differential equations problem, as seen by an
    029     * integrator is the time derivative <code>dY/dt</code> of a state
    030     * vector <code>Y</code>, both being one dimensional arrays. From the
    031     * integrator point of view, this derivative depends only on the
    032     * current time <code>t</code> and on the state vector
    033     * <code>Y</code>.</p>
    034     *
    035     * <p>For real problems, the derivative depends also on parameters
    036     * that do not belong to the state vector (dynamical model constants
    037     * for example). These constants are completely outside of the scope
    038     * of this interface, the classes that implement it are allowed to
    039     * handle them as they want.</p>
    040     *
    041     * @see FirstOrderIntegrator
    042     * @see FirstOrderConverter
    043     * @see SecondOrderDifferentialEquations
    044     *
    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 FirstOrderDifferentialEquations {
    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 placeholder array where to put the time derivative of the state vector
    060         * @throws DerivativeException this user-defined exception should be used if an error is
    061         * is triggered by user code
    062         */
    063        void computeDerivatives(double t, double[] y, double[] yDot)
    064            throws DerivativeException;
    065
    066    }