org.apache.commons.math3.ode.sampling.StepInterpolator.java Source code

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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.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.
 *
 * <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</em> 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</em> be copied using the dedicated
 * {@link #copy()} method.
 * </p>
 *
 * @see org.apache.commons.math3.ode.FirstOrderIntegrator
 * @see org.apache.commons.math3.ode.SecondOrderIntegrator
 * @see StepHandler
 * @version $Id: StepInterpolator.java 1416643 2012-12-03 19:37:14Z tn $
 * @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.
     * <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 #getInterpolatedDerivatives()
     * @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.
     * <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 #getInterpolatedState()
     * @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.
     * <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>
     * @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.
     * <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>
     * @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.
     * <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.
     * @see #setInterpolatedTime(double)
     * @exception MaxCountExceededException if the number of functions evaluations is exceeded
     * during step finalization
     */
    StepInterpolator copy() throws MaxCountExceededException;

}