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
21 /**
22 * This interface represents a handler that should be called after
23 * each successful fixed step.
24
25 * <p>This interface should be implemented by anyone who is interested
26 * in getting the solution of an ordinary differential equation at
27 * fixed time steps. Objects implementing this interface should be
28 * wrapped within an instance of {@link StepNormalizer} that itself
29 * is used as the general {@link StepHandler} by the integrator. The
30 * {@link StepNormalizer} object is called according to the integrator
31 * internal algorithms and it calls objects implementing this
32 * interface as necessary at fixed time steps.</p>
33 *
34 * @see StepHandler
35 * @see StepNormalizer
36 * @since 1.2
37 */
38
39 public interface FixedStepHandler {
40
41 /** Initialize step handler at the start of an ODE integration.
42 * <p>
43 * This method is called once at the start of the integration. It
44 * may be used by the step handler to initialize some internal data
45 * if needed.
46 * </p>
47 * @param t0 start value of the independent <i>time</i> variable
48 * @param y0 array containing the start value of the state vector
49 * @param t target time for the integration
50 */
51 void init(double t0, double[] y0, double t);
52
53 /**
54 * Handle the last accepted step.
55 * @param t time of the current step
56 * @param y state vector at t. For efficiency purposes, the {@link
57 * StepNormalizer} class reuses the same array on each call, so if
58 * the instance wants to keep it across all calls (for example to
59 * provide at the end of the integration a complete array of all
60 * steps), it should build a local copy store this copy.
61 * @param yDot derivatives of the state vector state vector at t.
62 * For efficiency purposes, the {@link StepNormalizer} class reuses
63 * the same array on each call, so if
64 * the instance wants to keep it across all calls (for example to
65 * provide at the end of the integration a complete array of all
66 * steps), it should build a local copy store this copy.
67 * @param isLast true if the step is the last one
68 */
69 void handleStep(double t, double[] y, double[] yDot, boolean isLast);
70 }