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.nonstiff;
19  
20  import org.apache.commons.math.ode.FirstOrderDifferentialEquations;
21  import org.apache.commons.math.ode.events.EventHandler;
22  
23  
24  public class StepProblem
25    implements FirstOrderDifferentialEquations, EventHandler {
26  
27    public StepProblem(double rateBefore, double rateAfter,
28                       double switchTime) {
29      this.rateAfter  = rateAfter;
30      this.switchTime = switchTime;
31      setRate(rateBefore);
32    }
33  
34    public void computeDerivatives(double t, double[] y, double[] yDot) {
35      yDot[0] = rate;
36    }
37  
38    public int getDimension() {
39      return 1;
40    }
41  
42    public void setRate(double rate) {
43      this.rate = rate;
44    }
45  
46    public int eventOccurred(double t, double[] y, boolean increasing) {
47      setRate(rateAfter);
48      return RESET_DERIVATIVES;
49    }
50  
51    public double g(double t, double[] y) {
52      return t - switchTime;
53    }
54  
55    public void resetState(double t, double[] y) {
56    }
57  
58    private double rate;
59    private double rateAfter;
60    private double switchTime;
61  
62    private static final long serialVersionUID = 7590601995477504318L;
63  
64  }