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 018package org.apache.commons.math4.legacy.ode; 019 020import org.apache.commons.math4.legacy.core.RealFieldElement; 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 FirstOrderFieldIntegrator 042 * 043 * @param <T> the type of the field elements 044 * @since 3.6 045 */ 046 047public interface FirstOrderFieldDifferentialEquations<T extends RealFieldElement<T>> { 048 049 /** Get the dimension of the problem. 050 * @return dimension of the problem 051 */ 052 int getDimension(); 053 054 /** Initialize equations at the start of an ODE integration. 055 * <p> 056 * This method is called once at the start of the integration. It 057 * may be used by the equations to initialize some internal data 058 * if needed. 059 * </p> 060 * @param t0 value of the independent <I>time</I> variable at integration start 061 * @param y0 array containing the value of the state vector at integration start 062 * @param finalTime target time for the integration 063 */ 064 void init(T t0, T[] y0, T finalTime); 065 066 /** Get the current time derivative of the state vector. 067 * @param t current value of the independent <I>time</I> variable 068 * @param y array containing the current value of the state vector 069 * @return time derivative of the state vector 070 */ 071 T[] computeDerivatives(T t, T[] y); 072}