analysis/org.eclipse.tracecompass.analysis.timing.core.tests/src/org/eclipse/tracecompass/analysis/timing/core/tests/segmentstore/statistics/OfflineStatisticsCalculator.java

   1 /*******************************************************************************
   2  * Copyright (c) 2016 Ericsson
   3  *
   4  * All rights reserved. This program and the accompanying materials are
   5  * made available under the terms of the Eclipse Public License v1.0 which
   6  * accompanies this distribution, and is available at
   7  * http://www.eclipse.org/legal/epl-v10.html
   8  *******************************************************************************/
   9
  10 package org.eclipse.tracecompass.analysis.timing.core.tests.segmentstore.statistics;
  11
  12 import java.util.Collection;
  13
  14 import org.eclipse.jdt.annotation.NonNull;
  15 import org.eclipse.tracecompass.analysis.os.linux.core.latency.SystemCall;
  16 import org.eclipse.tracecompass.segmentstore.core.ISegment;
  17
  18 /**
  19  * This calculates the statistics of a segment store in an offline manner to
  20  * validate online calculations.
  21  *
  22  * @author Matthew Khouzam
  23  *
  24  */
  25 public class OfflineStatisticsCalculator {
  26     private final Collection<@NonNull SystemCall> fSs;
  27
  28     /**
  29      * Constructor
  30      *
  31      * @param ss
  32      *            segment store, fully build
  33      */
  34     public OfflineStatisticsCalculator(Collection<@NonNull SystemCall> ss) {
  35         fSs = ss;
  36     }
  37
  38     /**
  39      * Get the max value
  40      *
  41      * @return the max value
  42      */
  43     public long getMax() {
  44         long max = Long.MIN_VALUE;
  45         for (ISegment interval : fSs) {
  46             max = Math.max(max, interval.getLength());
  47         }
  48         return max;
  49     }
  50
  51     /**
  52      * Get the min value
  53      *
  54      * @return the min value
  55      */
  56     public long getMin() {
  57         long min = Long.MAX_VALUE;
  58         for (ISegment interval : fSs) {
  59             min = Math.min(min, interval.getLength());
  60         }
  61         return min;
  62     }
  63
  64     /**
  65      * Get the average value
  66      *
  67      * @return the average value
  68      */
  69     public double getAvg() {
  70         double total = 0;
  71         for (ISegment interval : fSs) {
  72             total += (double) interval.getLength() / (double) fSs.size();
  73         }
  74         return total;
  75     }
  76
  77     /**
  78      * Get the standard deviation for a window.
  79      *
  80      * @return the standard deviation
  81      */
  82     public double getStdDev() {
  83         if (fSs.size() < 3) {
  84             return Double.NaN;
  85         }
  86         double mean = getAvg();
  87
  88         double totalVariance = 0;
  89         for (ISegment interval : fSs) {
  90             double result = interval.getLength() - mean;
  91             totalVariance += result * result / (fSs.size() - 1);
  92         }
  93         return Math.sqrt(totalVariance);
  94     }
  95 }