1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
|
/*
*
* Copyright 2015, Google Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following disclaimer
* in the documentation and/or other materials provided with the
* distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
/**
* Histogram module. Exports the Histogram class
* @module
*/
'use strict';
/**
* Histogram class. Collects data and exposes a histogram and other statistics.
* This data structure is taken directly from src/core/support/histogram.c, but
* pared down to the statistics needed for client stats in
* test/proto/benchmarks/stats.proto.
* @constructor
* @param {number} resolution The histogram's bucket resolution. Must be positive
* @param {number} max_possible The maximum allowed value. Must be greater than 1
*/
function Histogram(resolution, max_possible) {
this.resolution = resolution;
this.max_possible = max_possible;
this.sum = 0;
this.sum_of_squares = 0;
this.multiplier = 1 + resolution;
this.count = 0;
this.min_seen = max_possible;
this.max_seen = 0;
this.buckets = [];
for (var i = 0; i < this.bucketFor(max_possible) + 1; i++) {
this.buckets[i] = 0;
}
}
/**
* Get the bucket index for a given value.
* @param {number} value The value to check
* @return {number} The bucket index
*/
Histogram.prototype.bucketFor = function(value) {
return Math.floor(Math.log(value) / Math.log(this.multiplier));
};
/**
* Get the minimum value for a given bucket index
* @param {number} The bucket index to check
* @return {number} The minimum value for that bucket
*/
Histogram.prototype.bucketStart = function(index) {
return Math.pow(this.multiplier, index);
};
/**
* Add a value to the histogram. This updates all statistics with the new
* value. Those statistics should not be modified except with this function
* @param {number} value The value to add
*/
Histogram.prototype.add = function(value) {
// Ensure value is a number
value = +value;
this.sum += value;
this.sum_of_squares += value * value;
this.count++;
if (value < this.min_seen) {
this.min_seen = value;
}
if (value > this.max_seen) {
this.max_seen = value;
}
this.buckets[this.bucketFor(value)]++;
};
/**
* Get the mean of all added values
* @return {number} The mean
*/
Histogram.prototype.mean = function() {
return this.sum / this.count;
};
/**
* Get the variance of all added values. Used to calulate the standard deviation
* @return {number} The variance
*/
Histogram.prototype.variance = function() {
if (this.count == 0) {
return 0;
}
return (this.sum_of_squares * this.count - this.sum * this.sum) /
(this.count * this.count);
};
/**
* Get the standard deviation of all added values
* @return {number} The standard deviation
*/
Histogram.prototype.stddev = function() {
return Math.sqrt(this.variance);
};
/**
* Get the maximum among all added values
* @return {number} The maximum
*/
Histogram.prototype.maximum = function() {
return this.max_seen;
};
/**
* Get the minimum among all added values
* @return {number} The minimum
*/
Histogram.prototype.minimum = function() {
return this.min_seen;
};
/**
* Get the number of all added values
* @return {number} The count
*/
Histogram.prototype.getCount = function() {
return this.count;
};
/**
* Get the sum of all added values
* @return {number} The sum
*/
Histogram.prototype.getSum = function() {
return this.sum;
};
/**
* Get the sum of squares of all added values
* @return {number} The sum of squares
*/
Histogram.prototype.sumOfSquares = function() {
return this.sum_of_squares;
};
/**
* Get the raw histogram as a list of bucket sizes
* @return {Array.<number>} The buckets
*/
Histogram.prototype.getContents = function() {
return this.buckets;
};
module.exports = Histogram;
|
