class Hitimes::MutexedStats
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
Constants
- STATS
A list of the available stats
Attributes
Public Class Methods
# File lib/hitimes/stats.rb, line 42 def initialize @mutex = Mutex.new @min = Float::INFINITY @max = -Float::INFINITY @count = 0 @sum = 0.0 @sumsq = 0.0 end
Public Instance Methods
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;
# File lib/hitimes/stats.rb, line 74 def mean return 0.0 if @count.zero? return @sum / @count end
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.
# File lib/hitimes/stats.rb, line 92 def rate return 0.0 if @sum.zero? return @count / @sum end
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;
# File lib/hitimes/stats.rb, line 105 def stddev return 0.0 unless @count > 1 Math.sqrt((@sumsq - ((@sum * @sum)/@count)) / (@count - 1)) end
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.
# File lib/hitimes/stats.rb, line 122 def to_hash( *args ) h = {} args = [ args ].flatten args = STATS if args.empty? args.each do |meth| h[meth] = self.send( meth ) end return h end
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.
# File lib/hitimes/stats.rb, line 141 def to_json( *args ) h = to_hash( *args ) a = [] s = StringIO.new s.print "{ " h.each_pair do |k,v| a << "\"#{k}\": #{v}" end s.print a.join(", ") s.print "}" return s.string end
Update the running stats with the new value. Return the input value.
# File lib/hitimes/stats.rb, line 56 def update(value) @mutex.synchronize do @min = (value < @min) ? value : @min @max = (value > @max) ? value : @max @count += 1 @sum += value @sumsq += (value * value) end return value end