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1 | /******************************************************************************* |
2 | * Copyright (c) 2015 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.os.linux.core.tests.latency; | |
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 | } |