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package org.apache.commons.math3.ode.sampling;

import java.io.Externalizable;

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

/** This interface represents an interpolator over the last step
 * during an ODE integration.
 *
 * 

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).

*

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 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 must be copied using the dedicated * {@link #copy()} method. *

* * @see org.apache.commons.math3.ode.FirstOrderIntegrator * @see org.apache.commons.math3.ode.SecondOrderIntegrator * @see StepHandler * @since 1.2 */ public interface StepInterpolator 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. *

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.

*

Setting the time changes the instance internal state. This includes * the internal arrays returned in {@link #getInterpolatedState()}, * {@link #getInterpolatedDerivatives()}, {@link * #getInterpolatedSecondaryState(int)} and {@link * #getInterpolatedSecondaryDerivatives(int)}. So if their content must be preserved * across several calls, user must copy them.

* @param time time of the interpolated point * @see #getInterpolatedState() * @see #getInterpolatedDerivatives() * @see #getInterpolatedSecondaryState(int) * @see #getInterpolatedSecondaryDerivatives(int) */ void setInterpolatedTime(double time); /** * Get the state vector of the interpolated point. *

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 to the associated * {@link #setInterpolatedTime(double)} method.

* @return state vector at time {@link #getInterpolatedTime} * @see #getInterpolatedDerivatives() * @see #getInterpolatedSecondaryState(int) * @see #getInterpolatedSecondaryDerivatives(int) * @see #setInterpolatedTime(double) * @exception MaxCountExceededException if the number of functions evaluations is exceeded */ double[] getInterpolatedState() throws MaxCountExceededException; /** * Get the derivatives of the state vector of the interpolated point. *

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 to the associated * {@link #setInterpolatedTime(double)} method.

* @return derivatives of the state vector at time {@link #getInterpolatedTime} * @see #getInterpolatedState() * @see #getInterpolatedSecondaryState(int) * @see #getInterpolatedSecondaryDerivatives(int) * @see #setInterpolatedTime(double) * @since 2.0 * @exception MaxCountExceededException if the number of functions evaluations is exceeded */ double[] getInterpolatedDerivatives() throws MaxCountExceededException; /** Get the interpolated secondary state corresponding to the secondary equations. *

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 to the associated * {@link #setInterpolatedTime(double)} method.

* @param index index of the secondary set, as returned by {@link * org.apache.commons.math3.ode.ExpandableStatefulODE#addSecondaryEquations( * org.apache.commons.math3.ode.SecondaryEquations) * ExpandableStatefulODE.addSecondaryEquations(SecondaryEquations)} * @return interpolated secondary state at the current interpolation date * @see #getInterpolatedState() * @see #getInterpolatedDerivatives() * @see #getInterpolatedSecondaryDerivatives(int) * @see #setInterpolatedTime(double) * @since 3.0 * @exception MaxCountExceededException if the number of functions evaluations is exceeded */ double[] getInterpolatedSecondaryState(int index) throws MaxCountExceededException; /** Get the interpolated secondary derivatives corresponding to the secondary equations. *

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.

* @param index index of the secondary set, as returned by {@link * org.apache.commons.math3.ode.ExpandableStatefulODE#addSecondaryEquations( * org.apache.commons.math3.ode.SecondaryEquations) * ExpandableStatefulODE.addSecondaryEquations(SecondaryEquations)} * @return interpolated secondary derivatives at the current interpolation date * @see #getInterpolatedState() * @see #getInterpolatedDerivatives() * @see #getInterpolatedSecondaryState(int) * @see #setInterpolatedTime(double) * @since 3.0 * @exception MaxCountExceededException if the number of functions evaluations is exceeded */ double[] getInterpolatedSecondaryDerivatives(int index) throws MaxCountExceededException; /** Check if the natural integration direction is forward. *

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.

* @return true if the integration variable (time) increases during * integration */ boolean isForward(); /** Copy the instance. *

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.

* @return a deep copy of the instance, which can be used independently. * @see #setInterpolatedTime(double) * @exception MaxCountExceededException if the number of functions evaluations is exceeded * during step finalization */ StepInterpolator copy() throws MaxCountExceededException; }




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