| /* |
| * |
| * Copyright 2015 gRPC authors. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| * |
| */ |
| |
| /** |
| * 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; |