001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.commons.math3.ode.sampling;
019
020import org.apache.commons.math3.exception.MaxCountExceededException;
021
022
023/**
024 * This interface represents a handler that should be called after
025 * each successful step.
026 *
027 * <p>The ODE integrators compute the evolution of the state vector at
028 * some grid points that depend on their own internal algorithm. Once
029 * they have found a new grid point (possibly after having computed
030 * several evaluation of the derivative at intermediate points), they
031 * provide it to objects implementing this interface. These objects
032 * typically either ignore the intermediate steps and wait for the
033 * last one, store the points in an ephemeris, or forward them to
034 * specialized processing or output methods.</p>
035 *
036 * @see org.apache.commons.math3.ode.FirstOrderIntegrator
037 * @see org.apache.commons.math3.ode.SecondOrderIntegrator
038 * @see StepInterpolator
039 * @version $Id: StepHandler.java 1416643 2012-12-03 19:37:14Z tn $
040 * @since 1.2
041 */
042
043public interface StepHandler {
044
045    /** Initialize step handler at the start of an ODE integration.
046     * <p>
047     * This method is called once at the start of the integration. It
048     * may be used by the step handler to initialize some internal data
049     * if needed.
050     * </p>
051     * @param t0 start value of the independent <i>time</i> variable
052     * @param y0 array containing the start value of the state vector
053     * @param t target time for the integration
054     */
055    void init(double t0, double[] y0, double t);
056
057    /**
058     * Handle the last accepted step
059     * @param interpolator interpolator for the last accepted step. For
060     * efficiency purposes, the various integrators reuse the same
061     * object on each call, so if the instance wants to keep it across
062     * all calls (for example to provide at the end of the integration a
063     * continuous model valid throughout the integration range, as the
064     * {@link org.apache.commons.math3.ode.ContinuousOutputModel
065     * ContinuousOutputModel} class does), it should build a local copy
066     * using the clone method of the interpolator and store this copy.
067     * Keeping only a reference to the interpolator and reusing it will
068     * result in unpredictable behavior (potentially crashing the application).
069     * @param isLast true if the step is the last one
070     * @exception MaxCountExceededException if the interpolator throws one because
071     * the number of functions evaluations is exceeded
072     */
073    void handleStep(StepInterpolator interpolator, boolean isLast)
074        throws MaxCountExceededException;
075
076}