## The Commons Math *StepInterpolatorWithJacobians.java* source code

/*
* 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.math.ode.jacobians;
import java.io.Externalizable;
import org.apache.commons.math.ode.DerivativeException;
/** This interface represents an interpolator over the last step
* during an ODE integration.
*
* <p>The various ODE integrators provide objects implementing this
* interface to the step handlers. These objects are often custom
* objects tightly bound to the integrator internal algorithms. The
* handlers can use these objects to retrieve the state vector at
* intermediate times between the previous and the current grid points
* (this feature is often called dense output).</p>
* <p>One important thing to note is that the step handlers may be so
* tightly bound to the integrators that they often share some internal
* state arrays. This imply that one should <em>never use a direct
* reference to a step interpolator outside of the step handler, either
* for future use or for use in another thread. If such a need arise, the
* step interpolator <em>must be copied using the dedicated
* {@link #copy()} method.
* </p>
*
* @see FirstOrderIntegratorWithJacobians
* @see StepHandlerWithJacobians
* @version $Revision: 918702 $ $Date: 2010-03-03 16:28:16 -0500 (Wed, 03 Mar 2010) $
* @since 2.1
*/
public interface StepInterpolatorWithJacobians extends Externalizable {
/**
* Get the previous grid point time.
* @return previous grid point time
*/
double getPreviousTime();
/**
* Get the current grid point time.
* @return current grid point time
*/
double getCurrentTime();
/**
* Get the time of the interpolated point.
* If {@link #setInterpolatedTime} has not been called, it returns
* the current grid point time.
* @return interpolation point time
*/
double getInterpolatedTime();
/**
* Set the time of the interpolated point.
* <p>Setting the time outside of the current step is now allowed, but
* should be used with care since the accuracy of the interpolator will
* probably be very poor far from this step. This allowance has been
* added to simplify implementation of search algorithms near the
* step endpoints.</p>
* <p>Setting the time changes the instance internal state. If a
* specific state must be preserved, a copy of the instance must be
* created using {@link #copy()}.</p>
* @param time time of the interpolated point
*/
void setInterpolatedTime(double time);
/**
* Get the state vector of the interpolated point.
* <p>The returned vector is a reference to a reused array, so
* it should not be modified and it should be copied if it needs
* to be preserved across several calls.</p>
* @return state vector at time {@link #getInterpolatedTime}
* @see #getInterpolatedYDot()
* @throws DerivativeException if this call induces an automatic
* step finalization that throws one
*/
double[] getInterpolatedY() throws DerivativeException;
/**
* Get the partial derivatives of the state vector with respect to
* the initial state of the interpolated point.
* <p>The returned vector is a reference to a reused array, so
* it should not be modified and it should be copied if it needs
* to be preserved across several calls.</p>
* @return partial derivatives of the state vector with respect to
* the initial state at time {@link #getInterpolatedTime}
* @see #getInterpolatedY()
* @throws DerivativeException if this call induces an automatic
* step finalization that throws one
*/
double[][] getInterpolatedDyDy0() throws DerivativeException;
/**
* Get the partial derivatives of the state vector with respect to
* the ODE parameters of the interpolated point.
* <p>The returned vector is a reference to a reused array, so
* it should not be modified and it should be copied if it needs
* to be preserved across several calls.</p>
* @return partial derivatives of the state vector with respect to
* the ODE parameters at time {@link #getInterpolatedTime}
* @see #getInterpolatedY()
* @throws DerivativeException if this call induces an automatic
* step finalization that throws one
*/
double[][] getInterpolatedDyDp() throws DerivativeException;
/**
* Get the time derivatives of the state vector of the interpolated point.
* <p>The returned vector is a reference to a reused array, so
* it should not be modified and it should be copied if it needs
* to be preserved across several calls.</p>
* @return derivatives of the state vector at time {@link #getInterpolatedTime}
* @see #getInterpolatedY()
* @throws DerivativeException if this call induces an automatic
* step finalization that throws one
*/
double[] getInterpolatedYDot() throws DerivativeException;
/**
* Get the time derivatives of the jacobian of the state vector
* with respect to the initial state of the interpolated point.
* <p>The returned vector is a reference to a reused array, so
* it should not be modified and it should be copied if it needs
* to be preserved across several calls.</p>
* @return time derivatives of the jacobian of the state vector
* with respect to the initial state at time {@link #getInterpolatedTime}
* @see #getInterpolatedY()
* @throws DerivativeException if this call induces an automatic
* step finalization that throws one
*/
double[][] getInterpolatedDyDy0Dot() throws DerivativeException;
/**
* Get the time derivatives of the jacobian of the state vector
* with respect to the ODE parameters of the interpolated point.
* <p>The returned vector is a reference to a reused array, so
* it should not be modified and it should be copied if it needs
* to be preserved across several calls.</p>
* @return time derivatives of the jacobian of the state vector
* with respect to the ODE parameters at time {@link #getInterpolatedTime}
* @see #getInterpolatedY()
* @throws DerivativeException if this call induces an automatic
* step finalization that throws one
*/
double[][] getInterpolatedDyDpDot() throws DerivativeException;
/** Check if the natural integration direction is forward.
* <p>This method provides the integration direction as specified by
* the integrator itself, it avoid some nasty problems in
* degenerated cases like null steps due to cancellation at step
* initialization, step control or discrete events
* triggering.</p>
* @return true if the integration variable (time) increases during
* integration
*/
boolean isForward();
/** Copy the instance.
* <p>The copied instance is guaranteed to be independent from the
* original one. Both can be used with different settings for
* interpolated time without any side effect.</p>
* @return a deep copy of the instance, which can be used independently.
* @throws DerivativeException if this call induces an automatic
* step finalization that throws one
* @see #setInterpolatedTime(double)
*/
StepInterpolatorWithJacobians copy() throws DerivativeException;
}

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