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# hll-err.rb - Copyright (C) 2014 Salvatore Sanfilippo
# BSD license, See the COPYING file for more information.
#
# Check error of HyperLogLog Redis implementation for different set sizes.
require 'rubygems'
require 'redis'
require 'digest/sha1'
r = Redis.new
r.del('hll')
i = 0
while true do
100.times {
elements = []
1000.times {
ele = Digest::SHA1.hexdigest(i.to_s)
elements << ele
i += 1
}
r.pfadd('hll',*elements)
}
approx = r.pfcount('hll')
abs_err = (approx-i).abs
rel_err = 100.to_f*abs_err/i
puts "#{i} vs #{approx}: #{rel_err}%"
end
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