1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 package org.apache.commons.math4.legacy.ode.sampling;
19
20 import org.apache.commons.math4.legacy.exception.MaxCountExceededException;
21
22
23 /**
24 * This interface represents a handler that should be called after
25 * each successful step.
26 *
27 * <p>The ODE integrators compute the evolution of the state vector at
28 * some grid points that depend on their own internal algorithm. Once
29 * they have found a new grid point (possibly after having computed
30 * several evaluation of the derivative at intermediate points), they
31 * provide it to objects implementing this interface. These objects
32 * typically either ignore the intermediate steps and wait for the
33 * last one, store the points in an ephemeris, or forward them to
34 * specialized processing or output methods.</p>
35 *
36 * @see org.apache.commons.math4.legacy.ode.FirstOrderIntegrator
37 * @see org.apache.commons.math4.legacy.ode.SecondOrderIntegrator
38 * @see StepInterpolator
39 * @since 1.2
40 */
41
42 public interface StepHandler {
43
44 /** Initialize step handler at the start of an ODE integration.
45 * <p>
46 * This method is called once at the start of the integration. It
47 * may be used by the step handler to initialize some internal data
48 * if needed.
49 * </p>
50 * @param t0 start value of the independent <i>time</i> variable
51 * @param y0 array containing the start value of the state vector
52 * @param t target time for the integration
53 */
54 void init(double t0, double[] y0, double t);
55
56 /**
57 * Handle the last accepted step.
58 * @param interpolator interpolator for the last accepted step. For
59 * efficiency purposes, the various integrators reuse the same
60 * object on each call, so if the instance wants to keep it across
61 * all calls (for example to provide at the end of the integration a
62 * continuous model valid throughout the integration range, as the
63 * {@link org.apache.commons.math4.legacy.ode.ContinuousOutputModel
64 * ContinuousOutputModel} class does), it should build a local copy
65 * using the clone method of the interpolator and store this copy.
66 * Keeping only a reference to the interpolator and reusing it will
67 * result in unpredictable behavior (potentially crashing the application).
68 * @param isLast true if the step is the last one
69 * @exception MaxCountExceededException if the interpolator throws one because
70 * the number of functions evaluations is exceeded
71 */
72 void handleStep(StepInterpolator interpolator, boolean isLast)
73 throws MaxCountExceededException;
74 }