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view libs/commons-math-2.1/docs/apidocs/src-html/org/apache/commons/math/ode/sampling/StepNormalizer.html @ 13:cbf34dd4d7e6
commons-math-2.1 added
| 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.sampling;<a name="line.18"></a> <FONT color="green">019</FONT> <a name="line.19"></a> <FONT color="green">020</FONT> import org.apache.commons.math.ode.DerivativeException;<a name="line.20"></a> <FONT color="green">021</FONT> <a name="line.21"></a> <FONT color="green">022</FONT> /**<a name="line.22"></a> <FONT color="green">023</FONT> * This class wraps an object implementing {@link FixedStepHandler}<a name="line.23"></a> <FONT color="green">024</FONT> * into a {@link StepHandler}.<a name="line.24"></a> <FONT color="green">025</FONT> <a name="line.25"></a> <FONT color="green">026</FONT> * <p>This wrapper allows to use fixed step handlers with general<a name="line.26"></a> <FONT color="green">027</FONT> * integrators which cannot guaranty their integration steps will<a name="line.27"></a> <FONT color="green">028</FONT> * remain constant and therefore only accept general step<a name="line.28"></a> <FONT color="green">029</FONT> * handlers.</p><a name="line.29"></a> <FONT color="green">030</FONT> *<a name="line.30"></a> <FONT color="green">031</FONT> * <p>The stepsize used is selected at construction time. The {@link<a name="line.31"></a> <FONT color="green">032</FONT> * FixedStepHandler#handleStep handleStep} method of the underlying<a name="line.32"></a> <FONT color="green">033</FONT> * {@link FixedStepHandler} object is called at the beginning time of<a name="line.33"></a> <FONT color="green">034</FONT> * the integration t0 and also at times t0+h, t0+2h, ... If the<a name="line.34"></a> <FONT color="green">035</FONT> * integration range is an integer multiple of the stepsize, then the<a name="line.35"></a> <FONT color="green">036</FONT> * last point handled will be the endpoint of the integration tend, if<a name="line.36"></a> <FONT color="green">037</FONT> * not, the last point will belong to the interval [tend - h ;<a name="line.37"></a> <FONT color="green">038</FONT> * tend].</p><a name="line.38"></a> <FONT color="green">039</FONT> *<a name="line.39"></a> <FONT color="green">040</FONT> * <p>There is no constraint on the integrator, it can use any<a name="line.40"></a> <FONT color="green">041</FONT> * timestep it needs (time steps longer or shorter than the fixed time<a name="line.41"></a> <FONT color="green">042</FONT> * step and non-integer ratios are all allowed).</p><a name="line.42"></a> <FONT color="green">043</FONT> *<a name="line.43"></a> <FONT color="green">044</FONT> * @see StepHandler<a name="line.44"></a> <FONT color="green">045</FONT> * @see FixedStepHandler<a name="line.45"></a> <FONT color="green">046</FONT> * @version $Revision: 811833 $ $Date: 2009-09-06 12:27:50 -0400 (Sun, 06 Sep 2009) $<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 class StepNormalizer implements StepHandler {<a name="line.50"></a> <FONT color="green">051</FONT> <a name="line.51"></a> <FONT color="green">052</FONT> /** Fixed time step. */<a name="line.52"></a> <FONT color="green">053</FONT> private double h;<a name="line.53"></a> <FONT color="green">054</FONT> <a name="line.54"></a> <FONT color="green">055</FONT> /** Underlying step handler. */<a name="line.55"></a> <FONT color="green">056</FONT> private final FixedStepHandler handler;<a name="line.56"></a> <FONT color="green">057</FONT> <a name="line.57"></a> <FONT color="green">058</FONT> /** Last step time. */<a name="line.58"></a> <FONT color="green">059</FONT> private double lastTime;<a name="line.59"></a> <FONT color="green">060</FONT> <a name="line.60"></a> <FONT color="green">061</FONT> /** Last State vector. */<a name="line.61"></a> <FONT color="green">062</FONT> private double[] lastState;<a name="line.62"></a> <FONT color="green">063</FONT> <a name="line.63"></a> <FONT color="green">064</FONT> /** Last Derivatives vector. */<a name="line.64"></a> <FONT color="green">065</FONT> private double[] lastDerivatives;<a name="line.65"></a> <FONT color="green">066</FONT> <a name="line.66"></a> <FONT color="green">067</FONT> /** Integration direction indicator. */<a name="line.67"></a> <FONT color="green">068</FONT> private boolean forward;<a name="line.68"></a> <FONT color="green">069</FONT> <a name="line.69"></a> <FONT color="green">070</FONT> /** Simple constructor.<a name="line.70"></a> <FONT color="green">071</FONT> * @param h fixed time step (sign is not used)<a name="line.71"></a> <FONT color="green">072</FONT> * @param handler fixed time step handler to wrap<a name="line.72"></a> <FONT color="green">073</FONT> */<a name="line.73"></a> <FONT color="green">074</FONT> public StepNormalizer(final double h, final FixedStepHandler handler) {<a name="line.74"></a> <FONT color="green">075</FONT> this.h = Math.abs(h);<a name="line.75"></a> <FONT color="green">076</FONT> this.handler = handler;<a name="line.76"></a> <FONT color="green">077</FONT> reset();<a name="line.77"></a> <FONT color="green">078</FONT> }<a name="line.78"></a> <FONT color="green">079</FONT> <a name="line.79"></a> <FONT color="green">080</FONT> /** Determines whether this handler needs dense output.<a name="line.80"></a> <FONT color="green">081</FONT> * This handler needs dense output in order to provide data at<a name="line.81"></a> <FONT color="green">082</FONT> * regularly spaced steps regardless of the steps the integrator<a name="line.82"></a> <FONT color="green">083</FONT> * uses, so this method always returns true.<a name="line.83"></a> <FONT color="green">084</FONT> * @return always true<a name="line.84"></a> <FONT color="green">085</FONT> */<a name="line.85"></a> <FONT color="green">086</FONT> public boolean requiresDenseOutput() {<a name="line.86"></a> <FONT color="green">087</FONT> return true;<a name="line.87"></a> <FONT color="green">088</FONT> }<a name="line.88"></a> <FONT color="green">089</FONT> <a name="line.89"></a> <FONT color="green">090</FONT> /** Reset the step handler.<a name="line.90"></a> <FONT color="green">091</FONT> * Initialize the internal data as required before the first step is<a name="line.91"></a> <FONT color="green">092</FONT> * handled.<a name="line.92"></a> <FONT color="green">093</FONT> */<a name="line.93"></a> <FONT color="green">094</FONT> public void reset() {<a name="line.94"></a> <FONT color="green">095</FONT> lastTime = Double.NaN;<a name="line.95"></a> <FONT color="green">096</FONT> lastState = null;<a name="line.96"></a> <FONT color="green">097</FONT> lastDerivatives = null;<a name="line.97"></a> <FONT color="green">098</FONT> forward = true;<a name="line.98"></a> <FONT color="green">099</FONT> }<a name="line.99"></a> <FONT color="green">100</FONT> <a name="line.100"></a> <FONT color="green">101</FONT> /**<a name="line.101"></a> <FONT color="green">102</FONT> * Handle the last accepted step<a name="line.102"></a> <FONT color="green">103</FONT> * @param interpolator interpolator for the last accepted step. For<a name="line.103"></a> <FONT color="green">104</FONT> * efficiency purposes, the various integrators reuse the same<a name="line.104"></a> <FONT color="green">105</FONT> * object on each call, so if the instance wants to keep it across<a name="line.105"></a> <FONT color="green">106</FONT> * all calls (for example to provide at the end of the integration a<a name="line.106"></a> <FONT color="green">107</FONT> * continuous model valid throughout the integration range), it<a name="line.107"></a> <FONT color="green">108</FONT> * should build a local copy using the clone method and store this<a name="line.108"></a> <FONT color="green">109</FONT> * copy.<a name="line.109"></a> <FONT color="green">110</FONT> * @param isLast true if the step is the last one<a name="line.110"></a> <FONT color="green">111</FONT> * @throws DerivativeException this exception is propagated to the<a name="line.111"></a> <FONT color="green">112</FONT> * caller if the underlying user function triggers one<a name="line.112"></a> <FONT color="green">113</FONT> */<a name="line.113"></a> <FONT color="green">114</FONT> public void handleStep(final StepInterpolator interpolator, final boolean isLast)<a name="line.114"></a> <FONT color="green">115</FONT> throws DerivativeException {<a name="line.115"></a> <FONT color="green">116</FONT> <a name="line.116"></a> <FONT color="green">117</FONT> if (lastState == null) {<a name="line.117"></a> <FONT color="green">118</FONT> <a name="line.118"></a> <FONT color="green">119</FONT> lastTime = interpolator.getPreviousTime();<a name="line.119"></a> <FONT color="green">120</FONT> interpolator.setInterpolatedTime(lastTime);<a name="line.120"></a> <FONT color="green">121</FONT> lastState = interpolator.getInterpolatedState().clone();<a name="line.121"></a> <FONT color="green">122</FONT> lastDerivatives = interpolator.getInterpolatedDerivatives().clone();<a name="line.122"></a> <FONT color="green">123</FONT> <a name="line.123"></a> <FONT color="green">124</FONT> // take the integration direction into account<a name="line.124"></a> <FONT color="green">125</FONT> forward = interpolator.getCurrentTime() >= lastTime;<a name="line.125"></a> <FONT color="green">126</FONT> if (! forward) {<a name="line.126"></a> <FONT color="green">127</FONT> h = -h;<a name="line.127"></a> <FONT color="green">128</FONT> }<a name="line.128"></a> <FONT color="green">129</FONT> <a name="line.129"></a> <FONT color="green">130</FONT> }<a name="line.130"></a> <FONT color="green">131</FONT> <a name="line.131"></a> <FONT color="green">132</FONT> double nextTime = lastTime + h;<a name="line.132"></a> <FONT color="green">133</FONT> boolean nextInStep = forward ^ (nextTime > interpolator.getCurrentTime());<a name="line.133"></a> <FONT color="green">134</FONT> while (nextInStep) {<a name="line.134"></a> <FONT color="green">135</FONT> <a name="line.135"></a> <FONT color="green">136</FONT> // output the stored previous step<a name="line.136"></a> <FONT color="green">137</FONT> handler.handleStep(lastTime, lastState, lastDerivatives, false);<a name="line.137"></a> <FONT color="green">138</FONT> <a name="line.138"></a> <FONT color="green">139</FONT> // store the next step<a name="line.139"></a> <FONT color="green">140</FONT> lastTime = nextTime;<a name="line.140"></a> <FONT color="green">141</FONT> interpolator.setInterpolatedTime(lastTime);<a name="line.141"></a> <FONT color="green">142</FONT> System.arraycopy(interpolator.getInterpolatedState(), 0,<a name="line.142"></a> <FONT color="green">143</FONT> lastState, 0, lastState.length);<a name="line.143"></a> <FONT color="green">144</FONT> System.arraycopy(interpolator.getInterpolatedDerivatives(), 0,<a name="line.144"></a> <FONT color="green">145</FONT> lastDerivatives, 0, lastDerivatives.length);<a name="line.145"></a> <FONT color="green">146</FONT> <a name="line.146"></a> <FONT color="green">147</FONT> nextTime += h;<a name="line.147"></a> <FONT color="green">148</FONT> nextInStep = forward ^ (nextTime > interpolator.getCurrentTime());<a name="line.148"></a> <FONT color="green">149</FONT> <a name="line.149"></a> <FONT color="green">150</FONT> }<a name="line.150"></a> <FONT color="green">151</FONT> <a name="line.151"></a> <FONT color="green">152</FONT> if (isLast) {<a name="line.152"></a> <FONT color="green">153</FONT> // there will be no more steps,<a name="line.153"></a> <FONT color="green">154</FONT> // the stored one should be flagged as being the last<a name="line.154"></a> <FONT color="green">155</FONT> handler.handleStep(lastTime, lastState, lastDerivatives, true);<a name="line.155"></a> <FONT color="green">156</FONT> }<a name="line.156"></a> <FONT color="green">157</FONT> <a name="line.157"></a> <FONT color="green">158</FONT> }<a name="line.158"></a> <FONT color="green">159</FONT> <a name="line.159"></a> <FONT color="green">160</FONT> }<a name="line.160"></a> </PRE> </BODY> </HTML>