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90 lines
2.4 KiB
90 lines
2.4 KiB
# Copyright (c) 2005 Zed A. Shaw
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# You can redistribute it and/or modify it under the same terms as Ruby.
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#
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# Additional work donated by contributors. See http://mongrel.rubyforge.org/attributions.html
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# for more information.
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# A very simple little class for doing some basic fast statistics sampling.
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# You feed it either samples of numeric data you want measured or you call
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# Stats.tick to get it to add a time delta between the last time you called it.
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# When you're done either call sum, sumsq, n, min, max, mean or sd to get
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# the information. The other option is to just call dump and see everything.
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#
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# It does all of this very fast and doesn't take up any memory since the samples
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# are not stored but instead all the values are calculated on the fly.
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module Mongrel
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class Stats
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attr_reader :sum, :sumsq, :n, :min, :max
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def initialize(name)
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@name = name
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reset
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end
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# Resets the internal counters so you can start sampling again.
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def reset
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@sum = 0.0
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@sumsq = 0.0
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@last_time = Time.new
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@n = 0.0
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@min = 0.0
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@max = 0.0
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end
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# Adds a sampling to the calculations.
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def sample(s)
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@sum += s
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@sumsq += s * s
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if @n == 0
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@min = @max = s
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else
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@min = s if @min > s
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@max = s if @max < s
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end
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@n+=1
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end
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# Dump this Stats object with an optional additional message.
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def dump(msg = "", out=STDERR)
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out.puts "#{msg}: #{self.to_s}"
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end
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# Returns a common display (used by dump)
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def to_s
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"[#{@name}]: SUM=%0.4f, SUMSQ=%0.4f, N=%0.4f, MEAN=%0.4f, SD=%0.4f, MIN=%0.4f, MAX=%0.4f" % [@sum, @sumsq, @n, mean, sd, @min, @max]
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end
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# Calculates and returns the mean for the data passed so far.
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def mean
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@sum / @n
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end
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# Calculates the standard deviation of the data so far.
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def sd
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# (sqrt( ((s).sumsq - ( (s).sum * (s).sum / (s).n)) / ((s).n-1) ))
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begin
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return Math.sqrt( (@sumsq - ( @sum * @sum / @n)) / (@n-1) )
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rescue Errno::EDOM
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return 0.0
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end
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end
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# Adds a time delta between now and the last time you called this. This
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# will give you the average time between two activities.
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#
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# An example is:
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#
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# t = Stats.new("do_stuff")
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# 10000.times { do_stuff(); t.tick }
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# t.dump("time")
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#
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def tick
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now = Time.now
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sample(now - @last_time)
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@last_time = now
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end
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end
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end
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