src/ruby/qps/histogram.rb

#!/usr/bin/env ruby

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# Histogram class for use in performance testing and measurement

class Histogram
  # Determine the bucket index for a given value
  # @param {number} value The value to check
  # @return {number} The bucket index
  def bucket_for(value)
    (Math.log(value)/Math.log(@multiplier)).to_i
  end
  # Initialize an empty histogram
  # @param {number} resolution The resolution of the histogram
  # @param {number} max_possible The maximum value for the histogram
  def initialize(resolution, max_possible)
    @resolution=resolution
    @max_possible=max_possible
    @sum=0
    @sum_of_squares=0
    @multiplier=1+resolution
    @count=0
    @min_seen=max_possible
    @max_seen=0
    @buckets=Array.new(bucket_for(max_possible)+1, 0)
  end
  # 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
  def add(value)
    @sum += value
    @sum_of_squares += value * value
    @count += 1
    if value < @min_seen
      @min_seen = value
    end
    if value > @max_seen
      @max_seen = value
    end
    @buckets[bucket_for(value)] += 1
  end
  def minimum
    @min_seen
  end
  def maximum
    @max_seen
  end
  def sum
    @sum
  end
  def sum_of_squares
    @sum_of_squares
  end
  def count
    @count
  end
  def contents
    @buckets
  end
end