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.math.ode.sampling;
19
20 import org.apache.commons.math.ode.ContinuousOutputModel;
21 import org.apache.commons.math.ode.DerivativeException;
22 import org.apache.commons.math.ode.FirstOrderIntegrator;
23 import org.apache.commons.math.ode.SecondOrderIntegrator;
24
25 /**
26 * This interface represents a handler that should be called after
27 * each successful step.
28 *
29 * <p>The ODE integrators compute the evolution of the state vector at
30 * some grid points that depend on their own internal algorithm. Once
31 * they have found a new grid point (possibly after having computed
32 * several evaluation of the derivative at intermediate points), they
33 * provide it to objects implementing this interface. These objects
34 * typically either ignore the intermediate steps and wait for the
35 * last one, store the points in an ephemeris, or forward them to
36 * specialized processing or output methods.</p>
37 *
38 * @see FirstOrderIntegrator
39 * @see SecondOrderIntegrator
40 * @see StepInterpolator
41 * @version $Revision: 786881 $ $Date: 2009-06-20 14:53:08 -0400 (Sat, 20 Jun 2009) $
42 * @since 1.2
43 */
44
45 public interface StepHandler {
46
47 /** Determines whether this handler needs dense output.
48 * <p>This method allows the integrator to avoid performing extra
49 * computation if the handler does not need dense output. If this
50 * method returns false, the integrator will call the {@link
51 * #handleStep} method with a {@link DummyStepInterpolator} rather
52 * than a custom interpolator.</p>
53 * @return true if the handler needs dense output
54 */
55 public boolean requiresDenseOutput();
56
57 /** Reset the step handler.
58 * Initialize the internal data as required before the first step is
59 * handled.
60 */
61 public void reset();
62
63 /**
64 * Handle the last accepted step
65 * @param interpolator interpolator for the last accepted step. For
66 * efficiency purposes, the various integrators reuse the same
67 * object on each call, so if the instance wants to keep it across
68 * all calls (for example to provide at the end of the integration a
69 * continuous model valid throughout the integration range, as the
70 * {@link ContinuousOutputModel ContinuousOutputModel} class does),
71 * it should build a local copy using the clone method of the
72 * interpolator and store this copy. Keeping only a reference to the
73 * interpolator and reusing it will result in unpredictable
74 * behaviour (potentially crashing the application).
75 * @param isLast true if the step is the last one
76 * @throws DerivativeException this exception is propagated to the
77 * caller if the underlying user function triggers one
78 */
79 public void handleStep(StepInterpolator interpolator, boolean isLast)
80 throws DerivativeException;
81
82 }