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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;
/**
* This interface represents a second order differential equations set.
*
* <p>This interface should be implemented by all real second order differential equation problems
* before they can be handled by the integrators {@link SecondOrderIntegrator#integrate} method.
*
* <p>A second order differential equations problem, as seen by an integrator is the second time
* derivative <code>d2Y/dt^2</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>, on the state vector <code>Y</code> and on the first time derivative of the state
* vector.
*
* <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 SecondOrderIntegrator
* @see FirstOrderConverter
* @see FirstOrderDifferentialEquations
* @since 1.2
*/
public interface SecondOrderDifferentialEquations {
/**
* 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 <I>time</I> variable
* @param y array containing the current value of the state vector
* @param yDot array containing the current value of the first derivative of the state vector
* @param yDDot placeholder array where to put the second time derivative of the state vector
*/
void computeSecondDerivatives(double t, double[] y, double[] yDot, double[] yDDot);
}
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