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 * 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
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 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
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 * See the License for the specific language governing permissions and
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package org.apache.commons.math3.ode.sampling;

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


This interface represents a handler that should be called after
each successful step.
The ODE integrators compute the evolution of the state vector at
some grid points that depend on their own internal algorithm. Once
they have found a new grid point (possibly after having computed
several evaluation of the derivative at intermediate points), they
provide it to objects implementing this interface. These objects
typically either ignore the intermediate steps and wait for the
last one, store the points in an ephemeris, or forward them to
specialized processing or output methods.
See Also:
FirstOrderIntegrator
SecondOrderIntegrator
StepInterpolator
Since:
1.2/**
 * This interface represents a handler that should be called after
 * each successful step.
 *
 * <p>The ODE integrators compute the evolution of the state vector at
 * some grid points that depend on their own internal algorithm. Once
 * they have found a new grid point (possibly after having computed
 * several evaluation of the derivative at intermediate points), they
 * provide it to objects implementing this interface. These objects
 * typically either ignore the intermediate steps and wait for the
 * last one, store the points in an ephemeris, or forward them to
 * specialized processing or output methods.</p>
 *
 * @see org.apache.commons.math3.ode.FirstOrderIntegrator
 * @see org.apache.commons.math3.ode.SecondOrderIntegrator
 * @see StepInterpolator
 * @since 1.2
 */

public interface StepHandler {

    
Initialize step handler at the start of an ODE integration.

This method is called once at the start of the integration. It
may be used by the step handler to initialize some internal data
if needed.

Params:
t0 – start value of the independent time variable
y0 – array containing the start value of the state vector
t – target time for the integration/** Initialize step handler 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 step handler to initialize some internal data
     * if needed.
     * </p>
     * @param t0 start value of the independent <i>time</i> variable
     * @param y0 array containing the start value of the state vector
     * @param t target time for the integration
     */
    void init(double t0, double[] y0, double t);

    
Handle the last accepted step
Params:
interpolator – interpolator for the last accepted step. For efficiency purposes, the various integrators reuse the same object on each call, so if the instance wants to keep it across all calls (for example to provide at the end of the integration a continuous model valid throughout the integration range, as the 
ContinuousOutputModel class does), it should build a local copy using the clone method of the interpolator and store this copy. Keeping only a reference to the interpolator and reusing it will result in unpredictable behavior (potentially crashing the application).
isLast – true if the step is the last one
Throws:
MaxCountExceededException – if the interpolator throws one because
the number of functions evaluations is exceeded/**
     * Handle the last accepted step
     * @param interpolator interpolator for the last accepted step. For
     * efficiency purposes, the various integrators reuse the same
     * object on each call, so if the instance wants to keep it across
     * all calls (for example to provide at the end of the integration a
     * continuous model valid throughout the integration range, as the
     * {@link org.apache.commons.math3.ode.ContinuousOutputModel
     * ContinuousOutputModel} class does), it should build a local copy
     * using the clone method of the interpolator and store this copy.
     * Keeping only a reference to the interpolator and reusing it will
     * result in unpredictable behavior (potentially crashing the application).
     * @param isLast true if the step is the last one
     * @exception MaxCountExceededException if the interpolator throws one because
     * the number of functions evaluations is exceeded
     */
    void handleStep(StepInterpolator interpolator, boolean isLast)
        throws MaxCountExceededException;

}