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| author | dwinter |
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| date | Tue, 04 Jan 2011 10:02:07 +0100 |
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<HTML> <BODY BGCOLOR="white"> <PRE> <FONT color="green">001</FONT> /*<a name="line.1"></a> <FONT color="green">002</FONT> * Licensed to the Apache Software Foundation (ASF) under one or more<a name="line.2"></a> <FONT color="green">003</FONT> * contributor license agreements. See the NOTICE file distributed with<a name="line.3"></a> <FONT color="green">004</FONT> * this work for additional information regarding copyright ownership.<a name="line.4"></a> <FONT color="green">005</FONT> * The ASF licenses this file to You under the Apache License, Version 2.0<a name="line.5"></a> <FONT color="green">006</FONT> * (the "License"); you may not use this file except in compliance with<a name="line.6"></a> <FONT color="green">007</FONT> * the License. You may obtain a copy of the License at<a name="line.7"></a> <FONT color="green">008</FONT> *<a name="line.8"></a> <FONT color="green">009</FONT> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.9"></a> <FONT color="green">010</FONT> *<a name="line.10"></a> <FONT color="green">011</FONT> * Unless required by applicable law or agreed to in writing, software<a name="line.11"></a> <FONT color="green">012</FONT> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.12"></a> <FONT color="green">013</FONT> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.13"></a> <FONT color="green">014</FONT> * See the License for the specific language governing permissions and<a name="line.14"></a> <FONT color="green">015</FONT> * limitations under the License.<a name="line.15"></a> <FONT color="green">016</FONT> */<a name="line.16"></a> <FONT color="green">017</FONT> <a name="line.17"></a> <FONT color="green">018</FONT> package org.apache.commons.math.ode.events;<a name="line.18"></a> <FONT color="green">019</FONT> <a name="line.19"></a> <FONT color="green">020</FONT> /** This interface represents a handler for discrete events triggered<a name="line.20"></a> <FONT color="green">021</FONT> * during ODE integration.<a name="line.21"></a> <FONT color="green">022</FONT> *<a name="line.22"></a> <FONT color="green">023</FONT> * <p>Some events can be triggered at discrete times as an ODE problem<a name="line.23"></a> <FONT color="green">024</FONT> * is solved. This occurs for example when the integration process<a name="line.24"></a> <FONT color="green">025</FONT> * should be stopped as some state is reached (G-stop facility) when the<a name="line.25"></a> <FONT color="green">026</FONT> * precise date is unknown a priori, or when the derivatives have<a name="line.26"></a> <FONT color="green">027</FONT> * discontinuities, or simply when the user wants to monitor some<a name="line.27"></a> <FONT color="green">028</FONT> * states boundaries crossings.<a name="line.28"></a> <FONT color="green">029</FONT> * </p><a name="line.29"></a> <FONT color="green">030</FONT> *<a name="line.30"></a> <FONT color="green">031</FONT> * <p>These events are defined as occurring when a <code>g</code><a name="line.31"></a> <FONT color="green">032</FONT> * switching function sign changes.</p><a name="line.32"></a> <FONT color="green">033</FONT> *<a name="line.33"></a> <FONT color="green">034</FONT> * <p>Since events are only problem-dependent and are triggered by the<a name="line.34"></a> <FONT color="green">035</FONT> * independent <i>time</i> variable and the state vector, they can<a name="line.35"></a> <FONT color="green">036</FONT> * occur at virtually any time, unknown in advance. The integrators will<a name="line.36"></a> <FONT color="green">037</FONT> * take care to avoid sign changes inside the steps, they will reduce<a name="line.37"></a> <FONT color="green">038</FONT> * the step size when such an event is detected in order to put this<a name="line.38"></a> <FONT color="green">039</FONT> * event exactly at the end of the current step. This guarantees that<a name="line.39"></a> <FONT color="green">040</FONT> * step interpolation (which always has a one step scope) is relevant<a name="line.40"></a> <FONT color="green">041</FONT> * even in presence of discontinuities. This is independent from the<a name="line.41"></a> <FONT color="green">042</FONT> * stepsize control provided by integrators that monitor the local<a name="line.42"></a> <FONT color="green">043</FONT> * error (this event handling feature is available for all integrators,<a name="line.43"></a> <FONT color="green">044</FONT> * including fixed step ones).</p><a name="line.44"></a> <FONT color="green">045</FONT> *<a name="line.45"></a> <FONT color="green">046</FONT> * @version $Revision: 902214 $ $Date: 2010-01-22 13:40:28 -0500 (Fri, 22 Jan 2010) $<a name="line.46"></a> <FONT color="green">047</FONT> * @since 1.2<a name="line.47"></a> <FONT color="green">048</FONT> */<a name="line.48"></a> <FONT color="green">049</FONT> <a name="line.49"></a> <FONT color="green">050</FONT> public interface EventHandler {<a name="line.50"></a> <FONT color="green">051</FONT> <a name="line.51"></a> <FONT color="green">052</FONT> /** Stop indicator.<a name="line.52"></a> <FONT color="green">053</FONT> * <p>This value should be used as the return value of the {@link<a name="line.53"></a> <FONT color="green">054</FONT> * #eventOccurred eventOccurred} method when the integration should be<a name="line.54"></a> <FONT color="green">055</FONT> * stopped after the event ending the current step.</p><a name="line.55"></a> <FONT color="green">056</FONT> */<a name="line.56"></a> <FONT color="green">057</FONT> int STOP = 0;<a name="line.57"></a> <FONT color="green">058</FONT> <a name="line.58"></a> <FONT color="green">059</FONT> /** Reset state indicator.<a name="line.59"></a> <FONT color="green">060</FONT> * <p>This value should be used as the return value of the {@link<a name="line.60"></a> <FONT color="green">061</FONT> * #eventOccurred eventOccurred} method when the integration should<a name="line.61"></a> <FONT color="green">062</FONT> * go on after the event ending the current step, with a new state<a name="line.62"></a> <FONT color="green">063</FONT> * vector (which will be retrieved thanks to the {@link #resetState<a name="line.63"></a> <FONT color="green">064</FONT> * resetState} method).</p><a name="line.64"></a> <FONT color="green">065</FONT> */<a name="line.65"></a> <FONT color="green">066</FONT> int RESET_STATE = 1;<a name="line.66"></a> <FONT color="green">067</FONT> <a name="line.67"></a> <FONT color="green">068</FONT> /** Reset derivatives indicator.<a name="line.68"></a> <FONT color="green">069</FONT> * <p>This value should be used as the return value of the {@link<a name="line.69"></a> <FONT color="green">070</FONT> * #eventOccurred eventOccurred} method when the integration should<a name="line.70"></a> <FONT color="green">071</FONT> * go on after the event ending the current step, with a new derivatives<a name="line.71"></a> <FONT color="green">072</FONT> * vector (which will be retrieved thanks to the {@link<a name="line.72"></a> <FONT color="green">073</FONT> * org.apache.commons.math.ode.FirstOrderDifferentialEquations#computeDerivatives}<a name="line.73"></a> <FONT color="green">074</FONT> * method).</p><a name="line.74"></a> <FONT color="green">075</FONT> */<a name="line.75"></a> <FONT color="green">076</FONT> int RESET_DERIVATIVES = 2;<a name="line.76"></a> <FONT color="green">077</FONT> <a name="line.77"></a> <FONT color="green">078</FONT> /** Continue indicator.<a name="line.78"></a> <FONT color="green">079</FONT> * <p>This value should be used as the return value of the {@link<a name="line.79"></a> <FONT color="green">080</FONT> * #eventOccurred eventOccurred} method when the integration should go<a name="line.80"></a> <FONT color="green">081</FONT> * on after the event ending the current step.</p><a name="line.81"></a> <FONT color="green">082</FONT> */<a name="line.82"></a> <FONT color="green">083</FONT> int CONTINUE = 3;<a name="line.83"></a> <FONT color="green">084</FONT> <a name="line.84"></a> <FONT color="green">085</FONT> /** Compute the value of the switching function.<a name="line.85"></a> <FONT color="green">086</FONT> <a name="line.86"></a> <FONT color="green">087</FONT> * <p>The discrete events are generated when the sign of this<a name="line.87"></a> <FONT color="green">088</FONT> * switching function changes. The integrator will take care to change<a name="line.88"></a> <FONT color="green">089</FONT> * the stepsize in such a way these events occur exactly at step boundaries.<a name="line.89"></a> <FONT color="green">090</FONT> * The switching function must be continuous in its roots neighborhood<a name="line.90"></a> <FONT color="green">091</FONT> * (but not necessarily smooth), as the integrator will need to find its<a name="line.91"></a> <FONT color="green">092</FONT> * roots to locate precisely the events.</p><a name="line.92"></a> <FONT color="green">093</FONT> <a name="line.93"></a> <FONT color="green">094</FONT> * @param t current value of the independent <i>time</i> variable<a name="line.94"></a> <FONT color="green">095</FONT> * @param y array containing the current value of the state vector<a name="line.95"></a> <FONT color="green">096</FONT> * @return value of the g switching function<a name="line.96"></a> <FONT color="green">097</FONT> * @exception EventException if the switching function cannot be evaluated<a name="line.97"></a> <FONT color="green">098</FONT> */<a name="line.98"></a> <FONT color="green">099</FONT> double g(double t, double[] y) throws EventException;<a name="line.99"></a> <FONT color="green">100</FONT> <a name="line.100"></a> <FONT color="green">101</FONT> /** Handle an event and choose what to do next.<a name="line.101"></a> <FONT color="green">102</FONT> <a name="line.102"></a> <FONT color="green">103</FONT> * <p>This method is called when the integrator has accepted a step<a name="line.103"></a> <FONT color="green">104</FONT> * ending exactly on a sign change of the function, just <em>before</em><a name="line.104"></a> <FONT color="green">105</FONT> * the step handler itself is called (see below for scheduling). It<a name="line.105"></a> <FONT color="green">106</FONT> * allows the user to update his internal data to acknowledge the fact<a name="line.106"></a> <FONT color="green">107</FONT> * the event has been handled (for example setting a flag in the {@link<a name="line.107"></a> <FONT color="green">108</FONT> * org.apache.commons.math.ode.FirstOrderDifferentialEquations<a name="line.108"></a> <FONT color="green">109</FONT> * differential equations} to switch the derivatives computation in<a name="line.109"></a> <FONT color="green">110</FONT> * case of discontinuity), or to direct the integrator to either stop<a name="line.110"></a> <FONT color="green">111</FONT> * or continue integration, possibly with a reset state or derivatives.</p><a name="line.111"></a> <FONT color="green">112</FONT> <a name="line.112"></a> <FONT color="green">113</FONT> * <ul><a name="line.113"></a> <FONT color="green">114</FONT> * <li>if {@link #STOP} is returned, the step handler will be called<a name="line.114"></a> <FONT color="green">115</FONT> * with the <code>isLast</code> flag of the {@link<a name="line.115"></a> <FONT color="green">116</FONT> * org.apache.commons.math.ode.sampling.StepHandler#handleStep handleStep}<a name="line.116"></a> <FONT color="green">117</FONT> * method set to true and the integration will be stopped,</li><a name="line.117"></a> <FONT color="green">118</FONT> * <li>if {@link #RESET_STATE} is returned, the {@link #resetState<a name="line.118"></a> <FONT color="green">119</FONT> * resetState} method will be called once the step handler has<a name="line.119"></a> <FONT color="green">120</FONT> * finished its task, and the integrator will also recompute the<a name="line.120"></a> <FONT color="green">121</FONT> * derivatives,</li><a name="line.121"></a> <FONT color="green">122</FONT> * <li>if {@link #RESET_DERIVATIVES} is returned, the integrator<a name="line.122"></a> <FONT color="green">123</FONT> * will recompute the derivatives,<a name="line.123"></a> <FONT color="green">124</FONT> * <li>if {@link #CONTINUE} is returned, no specific action will<a name="line.124"></a> <FONT color="green">125</FONT> * be taken (apart from having called this method) and integration<a name="line.125"></a> <FONT color="green">126</FONT> * will continue.</li><a name="line.126"></a> <FONT color="green">127</FONT> * </ul><a name="line.127"></a> <FONT color="green">128</FONT> <a name="line.128"></a> <FONT color="green">129</FONT> * <p>The scheduling between this method and the {@link<a name="line.129"></a> <FONT color="green">130</FONT> * org.apache.commons.math.ode.sampling.StepHandler StepHandler} method {@link<a name="line.130"></a> <FONT color="green">131</FONT> * org.apache.commons.math.ode.sampling.StepHandler#handleStep(<a name="line.131"></a> <FONT color="green">132</FONT> * org.apache.commons.math.ode.sampling.StepInterpolator, boolean)<a name="line.132"></a> <FONT color="green">133</FONT> * handleStep(interpolator, isLast)} is to call this method first and<a name="line.133"></a> <FONT color="green">134</FONT> * <code>handleStep</code> afterwards. This scheduling allows the integrator to<a name="line.134"></a> <FONT color="green">135</FONT> * pass <code>true</code> as the <code>isLast</code> parameter to the step<a name="line.135"></a> <FONT color="green">136</FONT> * handler to make it aware the step will be the last one if this method<a name="line.136"></a> <FONT color="green">137</FONT> * returns {@link #STOP}. As the interpolator may be used to navigate back<a name="line.137"></a> <FONT color="green">138</FONT> * throughout the last step (as {@link<a name="line.138"></a> <FONT color="green">139</FONT> * org.apache.commons.math.ode.sampling.StepNormalizer StepNormalizer}<a name="line.139"></a> <FONT color="green">140</FONT> * does for example), user code called by this method and user<a name="line.140"></a> <FONT color="green">141</FONT> * code called by step handlers may experience apparently out of order values<a name="line.141"></a> <FONT color="green">142</FONT> * of the independent time variable. As an example, if the same user object<a name="line.142"></a> <FONT color="green">143</FONT> * implements both this {@link EventHandler EventHandler} interface and the<a name="line.143"></a> <FONT color="green">144</FONT> * {@link org.apache.commons.math.ode.sampling.FixedStepHandler FixedStepHandler}<a name="line.144"></a> <FONT color="green">145</FONT> * interface, a <em>forward</em> integration may call its<a name="line.145"></a> <FONT color="green">146</FONT> * <code>eventOccurred</code> method with t = 10 first and call its<a name="line.146"></a> <FONT color="green">147</FONT> * <code>handleStep</code> method with t = 9 afterwards. Such out of order<a name="line.147"></a> <FONT color="green">148</FONT> * calls are limited to the size of the integration step for {@link<a name="line.148"></a> <FONT color="green">149</FONT> * org.apache.commons.math.ode.sampling.StepHandler variable step handlers} and<a name="line.149"></a> <FONT color="green">150</FONT> * to the size of the fixed step for {@link<a name="line.150"></a> <FONT color="green">151</FONT> * org.apache.commons.math.ode.sampling.FixedStepHandler fixed step handlers}.</p><a name="line.151"></a> <FONT color="green">152</FONT> <a name="line.152"></a> <FONT color="green">153</FONT> * @param t current value of the independent <i>time</i> variable<a name="line.153"></a> <FONT color="green">154</FONT> * @param y array containing the current value of the state vector<a name="line.154"></a> <FONT color="green">155</FONT> * @param increasing if true, the value of the switching function increases<a name="line.155"></a> <FONT color="green">156</FONT> * when times increases around event (note that increase is measured with respect<a name="line.156"></a> <FONT color="green">157</FONT> * to physical time, not with respect to integration which may go backward in time)<a name="line.157"></a> <FONT color="green">158</FONT> * @return indication of what the integrator should do next, this<a name="line.158"></a> <FONT color="green">159</FONT> * value must be one of {@link #STOP}, {@link #RESET_STATE},<a name="line.159"></a> <FONT color="green">160</FONT> * {@link #RESET_DERIVATIVES} or {@link #CONTINUE}<a name="line.160"></a> <FONT color="green">161</FONT> * @exception EventException if the event occurrence triggers an error<a name="line.161"></a> <FONT color="green">162</FONT> */<a name="line.162"></a> <FONT color="green">163</FONT> int eventOccurred(double t, double[] y, boolean increasing) throws EventException;<a name="line.163"></a> <FONT color="green">164</FONT> <a name="line.164"></a> <FONT color="green">165</FONT> /** Reset the state prior to continue the integration.<a name="line.165"></a> <FONT color="green">166</FONT> <a name="line.166"></a> <FONT color="green">167</FONT> * <p>This method is called after the step handler has returned and<a name="line.167"></a> <FONT color="green">168</FONT> * before the next step is started, but only when {@link<a name="line.168"></a> <FONT color="green">169</FONT> * #eventOccurred} has itself returned the {@link #RESET_STATE}<a name="line.169"></a> <FONT color="green">170</FONT> * indicator. It allows the user to reset the state vector for the<a name="line.170"></a> <FONT color="green">171</FONT> * next step, without perturbing the step handler of the finishing<a name="line.171"></a> <FONT color="green">172</FONT> * step. If the {@link #eventOccurred} never returns the {@link<a name="line.172"></a> <FONT color="green">173</FONT> * #RESET_STATE} indicator, this function will never be called, and it is<a name="line.173"></a> <FONT color="green">174</FONT> * safe to leave its body empty.</p><a name="line.174"></a> <FONT color="green">175</FONT> <a name="line.175"></a> <FONT color="green">176</FONT> * @param t current value of the independent <i>time</i> variable<a name="line.176"></a> <FONT color="green">177</FONT> * @param y array containing the current value of the state vector<a name="line.177"></a> <FONT color="green">178</FONT> * the new state should be put in the same array<a name="line.178"></a> <FONT color="green">179</FONT> * @exception EventException if the state cannot be reseted<a name="line.179"></a> <FONT color="green">180</FONT> */<a name="line.180"></a> <FONT color="green">181</FONT> void resetState(double t, double[] y) throws EventException;<a name="line.181"></a> <FONT color="green">182</FONT> <a name="line.182"></a> <FONT color="green">183</FONT> }<a name="line.183"></a> </PRE> </BODY> </HTML>