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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.RealFieldElement;
/**
* This interface represents a first order differential equations set.
*
* <p>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.
*
* <p>A first order differential equations problem, as seen by an integrator is the time derivative
* <code>dY/dt</code> of a state vector <code>Y</code>, both being one dimensional arrays. From the
* integrator point of view, this derivative depends only on the current time <code>t</code> and on
* the state vector <code>Y</code>.
*
* <p>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 FirstOrderFieldIntegrator
* @param <T> the type of the field elements
* @since 3.6
*/
public interface FirstOrderFieldDifferentialEquations<T extends RealFieldElement<T>> {
/**
* Get the dimension of the problem.
*
* @return dimension of the problem
*/
int getDimension();
/**
* Initialize equations at the start of an ODE integration.
*
* <p>This method is called once at the start of the integration. It may be used by the
* equations to initialize some internal data if needed.
*
* @param t0 value of the independent <I>time</I> variable at integration start
* @param y0 array containing the value of the state vector at integration start
* @param finalTime target time for the integration
*/
void init(T t0, T[] y0, T finalTime);
/**
* Get the current time derivative of the state vector.
*
* @param t current value of the independent <I>time</I> variable
* @param y array containing the current value of the state vector
* @return time derivative of the state vector
*/
T[] computeDerivatives(T t, T[] y);
}
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