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    package org.apache.commons.math.ode;
018    
019    
020    /** This interface represents a first order differential equations set
021     * with a main set of equations and an extension set.
022     *
023     * <p>
024     * This interface is a simple extension on the {@link
025     * FirstOrderDifferentialEquations} that allows to identify which part
026     * of a complete set of differential equations correspond to the main
027     * set and which part correspond to the extension set.
028     * </p>
029     * <p>
030     * One typical use case is the computation of Jacobians. The main
031     * set of equations correspond to the raw ode, and we add to this set
032     * another bunch of equations which represent the jacobians of the
033     * main set. In that case, we want the integrator to use <em>only</em>
034     * the main set to estimate the errors and hence the step sizes. It should
035     * <em>not</em> use the additional equations in this computation. If the
036     * complete ode implements this interface, the {@link FirstOrderIntegrator
037     * integrator} will be able to know where the main set ends and where the
038     * extended set begins.
039     * </p>
040     * <p>
041     * We consider that the main set always corresponds to the first equations
042     * and the extended set to the last equations.
043     * </p>
044     *
045     * @see FirstOrderDifferentialEquations
046     *
047     * @version $Revision: 980981 $ $Date: 2010-07-31 00:03:04 +0200 (sam. 31 juil. 2010) $
048     * @since 2.2
049     */
050    
051    public interface ExtendedFirstOrderDifferentialEquations extends FirstOrderDifferentialEquations {
052    
053        /** Return the dimension of the main set of equations.
054         * <p>
055         * The main set of equations represent the first part of an ODE state.
056         * The error estimations and adaptive step size computation should be
057         * done on this first part only, not on the final part of the state
058         * which represent an extension set of equations which are considered
059         * secondary.
060         * </p>
061         * @return dimension of the main set of equations, must be lesser than or
062         * equal to the {@link #getDimension() total dimension}
063         */
064        int getMainSetDimension();
065    
066    }