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| <pre><span class="sourceLineNo">001</span>/**<a name="line.1"></a> |
| <span class="sourceLineNo">002</span> *<a name="line.2"></a> |
| <span class="sourceLineNo">003</span> * Licensed to the Apache Software Foundation (ASF) under one<a name="line.3"></a> |
| <span class="sourceLineNo">004</span> * or more contributor license agreements. See the NOTICE file<a name="line.4"></a> |
| <span class="sourceLineNo">005</span> * distributed with this work for additional information<a name="line.5"></a> |
| <span class="sourceLineNo">006</span> * regarding copyright ownership. The ASF licenses this file<a name="line.6"></a> |
| <span class="sourceLineNo">007</span> * to you under the Apache License, Version 2.0 (the<a name="line.7"></a> |
| <span class="sourceLineNo">008</span> * "License"); you may not use this file except in compliance<a name="line.8"></a> |
| <span class="sourceLineNo">009</span> * with the License. You may obtain a copy of the License at<a name="line.9"></a> |
| <span class="sourceLineNo">010</span> *<a name="line.10"></a> |
| <span class="sourceLineNo">011</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.11"></a> |
| <span class="sourceLineNo">012</span> *<a name="line.12"></a> |
| <span class="sourceLineNo">013</span> * Unless required by applicable law or agreed to in writing, software<a name="line.13"></a> |
| <span class="sourceLineNo">014</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.14"></a> |
| <span class="sourceLineNo">015</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.15"></a> |
| <span class="sourceLineNo">016</span> * See the License for the specific language governing permissions and<a name="line.16"></a> |
| <span class="sourceLineNo">017</span> * limitations under the License.<a name="line.17"></a> |
| <span class="sourceLineNo">018</span> */<a name="line.18"></a> |
| <span class="sourceLineNo">019</span><a name="line.19"></a> |
| <span class="sourceLineNo">020</span>package org.apache.hadoop.hbase.util;<a name="line.20"></a> |
| <span class="sourceLineNo">021</span><a name="line.21"></a> |
| <span class="sourceLineNo">022</span>import org.apache.yetus.audience.InterfaceAudience;<a name="line.22"></a> |
| <span class="sourceLineNo">023</span><a name="line.23"></a> |
| <span class="sourceLineNo">024</span>/**<a name="line.24"></a> |
| <span class="sourceLineNo">025</span> * This class maintains mean and variation for any sequence of input provided to it.<a name="line.25"></a> |
| <span class="sourceLineNo">026</span> * It is initialized with number of rolling periods which basically means the number of past<a name="line.26"></a> |
| <span class="sourceLineNo">027</span> * inputs whose data will be considered to maintain mean and variation.<a name="line.27"></a> |
| <span class="sourceLineNo">028</span> * It will use O(N) memory to maintain these statistics, where N is number of look up periods it<a name="line.28"></a> |
| <span class="sourceLineNo">029</span> * was initialized with.<a name="line.29"></a> |
| <span class="sourceLineNo">030</span> * If zero is passed during initialization then it will maintain mean and variance from the<a name="line.30"></a> |
| <span class="sourceLineNo">031</span> * start. It will use O(1) memory only. But note that since it will maintain mean / variance<a name="line.31"></a> |
| <span class="sourceLineNo">032</span> * from the start the statistics may behave like constants and may ignore short trends.<a name="line.32"></a> |
| <span class="sourceLineNo">033</span> * All operations are O(1) except the initialization which is O(N).<a name="line.33"></a> |
| <span class="sourceLineNo">034</span> */<a name="line.34"></a> |
| <span class="sourceLineNo">035</span>@InterfaceAudience.Private<a name="line.35"></a> |
| <span class="sourceLineNo">036</span>public class RollingStatCalculator {<a name="line.36"></a> |
| <span class="sourceLineNo">037</span> private double currentSum;<a name="line.37"></a> |
| <span class="sourceLineNo">038</span> private double currentSqrSum;<a name="line.38"></a> |
| <span class="sourceLineNo">039</span> // Total number of data values whose statistic is currently present<a name="line.39"></a> |
| <span class="sourceLineNo">040</span> private long numberOfDataValues;<a name="line.40"></a> |
| <span class="sourceLineNo">041</span> private int rollingPeriod;<a name="line.41"></a> |
| <span class="sourceLineNo">042</span> private int currentIndexPosition;<a name="line.42"></a> |
| <span class="sourceLineNo">043</span> // to be used only if we have non-zero rolling period<a name="line.43"></a> |
| <span class="sourceLineNo">044</span> private long [] dataValues;<a name="line.44"></a> |
| <span class="sourceLineNo">045</span><a name="line.45"></a> |
| <span class="sourceLineNo">046</span> /**<a name="line.46"></a> |
| <span class="sourceLineNo">047</span> * Creates a RollingStatCalculator with given number of rolling periods.<a name="line.47"></a> |
| <span class="sourceLineNo">048</span> * @param rollingPeriod<a name="line.48"></a> |
| <span class="sourceLineNo">049</span> */<a name="line.49"></a> |
| <span class="sourceLineNo">050</span> public RollingStatCalculator(int rollingPeriod) {<a name="line.50"></a> |
| <span class="sourceLineNo">051</span> this.rollingPeriod = rollingPeriod;<a name="line.51"></a> |
| <span class="sourceLineNo">052</span> this.dataValues = fillWithZeros(rollingPeriod);<a name="line.52"></a> |
| <span class="sourceLineNo">053</span> this.currentSum = 0.0;<a name="line.53"></a> |
| <span class="sourceLineNo">054</span> this.currentSqrSum = 0.0;<a name="line.54"></a> |
| <span class="sourceLineNo">055</span> this.currentIndexPosition = 0;<a name="line.55"></a> |
| <span class="sourceLineNo">056</span> this.numberOfDataValues = 0;<a name="line.56"></a> |
| <span class="sourceLineNo">057</span> }<a name="line.57"></a> |
| <span class="sourceLineNo">058</span><a name="line.58"></a> |
| <span class="sourceLineNo">059</span> /**<a name="line.59"></a> |
| <span class="sourceLineNo">060</span> * Inserts given data value to array of data values to be considered for statistics calculation<a name="line.60"></a> |
| <span class="sourceLineNo">061</span> * @param data<a name="line.61"></a> |
| <span class="sourceLineNo">062</span> */<a name="line.62"></a> |
| <span class="sourceLineNo">063</span> public void insertDataValue(long data) {<a name="line.63"></a> |
| <span class="sourceLineNo">064</span> // if current number of data points already equals rolling period and rolling period is<a name="line.64"></a> |
| <span class="sourceLineNo">065</span> // non-zero then remove one data and update the statistics<a name="line.65"></a> |
| <span class="sourceLineNo">066</span> if(numberOfDataValues >= rollingPeriod && rollingPeriod > 0) {<a name="line.66"></a> |
| <span class="sourceLineNo">067</span> this.removeData(dataValues[currentIndexPosition]);<a name="line.67"></a> |
| <span class="sourceLineNo">068</span> }<a name="line.68"></a> |
| <span class="sourceLineNo">069</span> numberOfDataValues++;<a name="line.69"></a> |
| <span class="sourceLineNo">070</span> currentSum = currentSum + (double)data;<a name="line.70"></a> |
| <span class="sourceLineNo">071</span> currentSqrSum = currentSqrSum + ((double)data * data);<a name="line.71"></a> |
| <span class="sourceLineNo">072</span> if (rollingPeriod >0)<a name="line.72"></a> |
| <span class="sourceLineNo">073</span> {<a name="line.73"></a> |
| <span class="sourceLineNo">074</span> dataValues[currentIndexPosition] = data;<a name="line.74"></a> |
| <span class="sourceLineNo">075</span> currentIndexPosition = (currentIndexPosition + 1) % rollingPeriod;<a name="line.75"></a> |
| <span class="sourceLineNo">076</span> }<a name="line.76"></a> |
| <span class="sourceLineNo">077</span> }<a name="line.77"></a> |
| <span class="sourceLineNo">078</span><a name="line.78"></a> |
| <span class="sourceLineNo">079</span> /**<a name="line.79"></a> |
| <span class="sourceLineNo">080</span> * Update the statistics after removing the given data value<a name="line.80"></a> |
| <span class="sourceLineNo">081</span> * @param data<a name="line.81"></a> |
| <span class="sourceLineNo">082</span> */<a name="line.82"></a> |
| <span class="sourceLineNo">083</span> private void removeData(long data) {<a name="line.83"></a> |
| <span class="sourceLineNo">084</span> currentSum = currentSum - (double)data;<a name="line.84"></a> |
| <span class="sourceLineNo">085</span> currentSqrSum = currentSqrSum - ((double)data * data);<a name="line.85"></a> |
| <span class="sourceLineNo">086</span> numberOfDataValues--;<a name="line.86"></a> |
| <span class="sourceLineNo">087</span> }<a name="line.87"></a> |
| <span class="sourceLineNo">088</span><a name="line.88"></a> |
| <span class="sourceLineNo">089</span> /**<a name="line.89"></a> |
| <span class="sourceLineNo">090</span> * @return mean of the data values that are in the current list of data values<a name="line.90"></a> |
| <span class="sourceLineNo">091</span> */<a name="line.91"></a> |
| <span class="sourceLineNo">092</span> public double getMean() {<a name="line.92"></a> |
| <span class="sourceLineNo">093</span> return this.currentSum / (double)numberOfDataValues;<a name="line.93"></a> |
| <span class="sourceLineNo">094</span> }<a name="line.94"></a> |
| <span class="sourceLineNo">095</span><a name="line.95"></a> |
| <span class="sourceLineNo">096</span> /**<a name="line.96"></a> |
| <span class="sourceLineNo">097</span> * @return deviation of the data values that are in the current list of data values<a name="line.97"></a> |
| <span class="sourceLineNo">098</span> */<a name="line.98"></a> |
| <span class="sourceLineNo">099</span> public double getDeviation() {<a name="line.99"></a> |
| <span class="sourceLineNo">100</span> double variance = (currentSqrSum - (currentSum*currentSum)/(double)(numberOfDataValues))/<a name="line.100"></a> |
| <span class="sourceLineNo">101</span> numberOfDataValues;<a name="line.101"></a> |
| <span class="sourceLineNo">102</span> return Math.sqrt(variance);<a name="line.102"></a> |
| <span class="sourceLineNo">103</span> }<a name="line.103"></a> |
| <span class="sourceLineNo">104</span><a name="line.104"></a> |
| <span class="sourceLineNo">105</span> /**<a name="line.105"></a> |
| <span class="sourceLineNo">106</span> * @param size<a name="line.106"></a> |
| <span class="sourceLineNo">107</span> * @return an array of given size initialized with zeros<a name="line.107"></a> |
| <span class="sourceLineNo">108</span> */<a name="line.108"></a> |
| <span class="sourceLineNo">109</span> private long [] fillWithZeros(int size) {<a name="line.109"></a> |
| <span class="sourceLineNo">110</span> long [] zeros = new long [size];<a name="line.110"></a> |
| <span class="sourceLineNo">111</span> for (int i=0; i<size; i++) {<a name="line.111"></a> |
| <span class="sourceLineNo">112</span> zeros[i] = 0L;<a name="line.112"></a> |
| <span class="sourceLineNo">113</span> }<a name="line.113"></a> |
| <span class="sourceLineNo">114</span> return zeros;<a name="line.114"></a> |
| <span class="sourceLineNo">115</span> }<a name="line.115"></a> |
| <span class="sourceLineNo">116</span>}<a name="line.116"></a> |
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