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A Java's Collaborative Filtering library to carry out experiments in research of Collaborative Filtering based Recommender Systems. The library has been designed from researchers to researchers.

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.math3.ode;

import org.apache.commons.math3.exception.DimensionMismatchException;
import org.apache.commons.math3.exception.MaxCountExceededException;



/** This interface represents a first order differential equations set.
 *
 * This interface should be implemented by all real first order
 * differential equation problems before they can be handled by the
 * integrators {@link FirstOrderIntegrator#integrate} method.
 *
 * A first order differential equations problem, as seen by an
 * integrator is the time derivative dY/dt of a state
 * vector Y, both being one dimensional arrays. From the
 * integrator point of view, this derivative depends only on the
 * current time t and on the state vector
 * Y.
 *
 * For real problems, the derivative depends also on parameters
 * that do not belong to the state vector (dynamical model constants
 * for example). These constants are completely outside of the scope
 * of this interface, the classes that implement it are allowed to
 * handle them as they want.
 *
 * @see FirstOrderIntegrator
 * @see FirstOrderConverter
 * @see SecondOrderDifferentialEquations
 *
 * @since 1.2
 */

public interface FirstOrderDifferentialEquations {

    /** Get the dimension of the problem.
     * @return dimension of the problem
     */
    int getDimension();

    /** Get the current time derivative of the state vector.
     * @param t current value of the independent time variable
     * @param y array containing the current value of the state vector
     * @param yDot placeholder array where to put the time derivative of the state vector
     * @exception MaxCountExceededException if the number of functions evaluations is exceeded
     * @exception DimensionMismatchException if arrays dimensions do not match equations settings
     */
    void computeDerivatives(double t, double[] y, double[] yDot)
        throws MaxCountExceededException, DimensionMismatchException;

}