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# frozen_string_literal: true
#--
# Copyright (c) 2008, 2009 Jeremy Hinegardner
# All rights reserved. See LICENSE and/or COPYING for details.
#++
require "stringio"
module Hitimes
#
# The Stats class encapulsates capturing and reporting statistics. It is
# modeled after the RFuzz::Sampler class, but implemented in C. For general use
# you allocate a new Stats object, and then update it with new values. The
# Stats object will keep track of the _min_, _max_, _count_, _sum_ and _sumsq_
# and when you want you may also retrieve the _mean_, _stddev_ and _rate_.
#
# this contrived example shows getting a list of all the files in a directory
# and running stats on file sizes.
#
# s = Hitimes::Stats.new
# dir = ARGV.shift || Dir.pwd
# Dir.entries( dir ).each do |entry|
# fs = File.stat( entry )
# if fs.file? then
# s.update( fs.size )
# end
# end
#
# %w[ count min max mean sum stddev rate ].each do |m|
# puts "#{m.rjust(6)} : #{s.send( m ) }"
# end
#
class Stats
# A list of the available stats
STATS = %w[count max mean min rate stddev sum sumsq].freeze
attr_reader :min, :max, :count, :sum, :sumsq
def initialize
@mutex = Mutex.new
@min = Float::INFINITY
@max = -Float::INFINITY
@count = 0
@sum = 0.0
@sumsq = 0.0
end
# call-seq:
# stat.update( val ) -> val
#
# Update the running stats with the new value.
# Return the input value.
def update(value)
@mutex.synchronize do
@min = (value < @min) ? value : @min
@max = (value > @max) ? value : @max
@count += 1
@sum += value
@sumsq += (value * value)
end
value
end
# call-seq:
# stat.mean -> Float
#
# Return the arithmetic mean of the values put into the Stats object. If no
# values have passed through the stats object then 0.0 is returned;
def mean
return 0.0 if @count.zero?
@sum / @count
end
# call-seq:
# stat.rate -> Float
#
# Return the +count+ divided by +sum+.
#
# In many cases when Stats#update( _value_ ) is called, the _value_ is a unit
# of time, typically seconds or microseconds. #rate is a convenience for those
# times. In this case, where _value_ is a unit if time, then count divided by
# sum is a useful value, i.e. +something per unit of time+.
#
# In the case where _value_ is a non-time related value, then the value
# returned by _rate_ is not really useful.
#
def rate
return 0.0 if @sum.zero?
@count / @sum
end
#
# call-seq:
# stat.stddev -> Float
#
# Return the standard deviation of all the values that have passed through the
# Stats object. The standard deviation has no meaning unless the count is > 1,
# therefore if the current _stat.count_ is < 1 then 0.0 will be returned;
#
def stddev
return 0.0 unless @count > 1
Math.sqrt((@sumsq - ((@sum * @sum) / @count)) / (@count - 1))
end
#
# call-seq:
# stat.to_hash -> Hash
# stat.to_hash( %w[ count max mean ]) -> Hash
#
# return a hash of the stats. By default this returns a hash of all stats
# but passing in an array of items will limit the stats returned to only
# those in the Array.
#
# If passed in an empty array or nil to to_hash then STATS is assumed to be
# the list of stats to return in the hash.
#
def to_hash(*args)
result = {}
fields = [args].flatten
fields = STATS if fields.empty?
fields.each do |meth|
result[meth] = send(meth)
end
result
end
#
# call-seq:
# stat.to_json -> String
# stat.to_json( *args ) -> String
#
# return a json string of the stats. By default this returns a json string
# of all the stats. If an array of items is passed in, those that match the
# known stats will be all that is included in the json output.
#
def to_json(*args)
stats = to_hash(*args)
slugs = []
out = StringIO.new
out.print "{ "
stats.each_pair do |key, val|
slugs << "\"#{key}\": #{val}"
end
out.print slugs.join(", ")
out.print "}"
out.string
end
end
end
|
