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 */ 017 018 package org.apache.commons.math.ode.nonstiff; 019 020 import org.apache.commons.math.ode.FirstOrderDifferentialEquations; 021 import org.apache.commons.math.ode.events.EventHandler; 022 023 024 public class StepProblem 025 implements FirstOrderDifferentialEquations, EventHandler { 026 027 public StepProblem(double rateBefore, double rateAfter, 028 double switchTime) { 029 this.rateAfter = rateAfter; 030 this.switchTime = switchTime; 031 setRate(rateBefore); 032 } 033 034 public void computeDerivatives(double t, double[] y, double[] yDot) { 035 yDot[0] = rate; 036 } 037 038 public int getDimension() { 039 return 1; 040 } 041 042 public void setRate(double rate) { 043 this.rate = rate; 044 } 045 046 public int eventOccurred(double t, double[] y, boolean increasing) { 047 setRate(rateAfter); 048 return RESET_DERIVATIVES; 049 } 050 051 public double g(double t, double[] y) { 052 return t - switchTime; 053 } 054 055 public void resetState(double t, double[] y) { 056 } 057 058 private double rate; 059 private double rateAfter; 060 private double switchTime; 061 062 private static final long serialVersionUID = 7590601995477504318L; 063 064 }