# hll-err.rb - Copyright (C) 2014 Salvatore Sanfilippo
# BSD license, See the COPYING file for more information.
#
# This program is suited to output average and maximum errors of
# the Redis HyperLogLog implementation in a format suitable to print
# graphs using gnuplot.

require 'rubygems'
require 'redis'
require 'digest/sha1'

# Generate an array of [cardinality,relative_error] pairs
# in the 0 - max range, with the specified step.
#
# 'r' is the Redis object used to perform the queries.
# 'seed' must be different every time you want a test performed
# with a different set. The function guarantees that if 'seed' is the
# same, exactly the same dataset is used, and when it is different,
# a totally unrelated different data set is used (without any common
# element in practice).
def run_experiment(r,seed,max,step)
    r.del('hll')
    i = 0
    samples = []
    step = 1000 if step > 1000
    while i < max do
        elements = []
        step.times {
            ele = Digest::SHA1.hexdigest(i.to_s+seed.to_s)
            elements << ele
            i += 1
        }
        r.pfadd('hll',*elements)
        approx = r.pfcount('hll')
        err = approx-i
        rel_err = 100.to_f*err/i
        samples << [i,rel_err]
    end
    samples
end

def filter_samples(numsets,max,step,filter)
    r = Redis.new
    dataset = {}
    (0...numsets).each{|i|
        dataset[i] = run_experiment(r,i,max,step)
        STDERR.puts "Set #{i}"
    }
    dataset[0].each_with_index{|ele,index|
        if filter == :max
            card=ele[0]
            err=ele[1].abs
            (1...numsets).each{|i|
                err = dataset[i][index][1] if err < dataset[i][index][1]
            }
            puts "#{card} #{err}"
        elsif filter == :avg
            card=ele[0]
            err = 0
            (0...numsets).each{|i|
                err += dataset[i][index][1]
            }
            err /= numsets
            puts "#{card} #{err}"
        elsif filter == :absavg
            card=ele[0]
            err = 0
            (0...numsets).each{|i|
                err += dataset[i][index][1].abs
            }
            err /= numsets
            puts "#{card} #{err}"
        elsif filter == :all
            (0...numsets).each{|i|
                card,err = dataset[i][index]
                puts "#{card} #{err}"
            }
        else
            raise "Unknown filter #{filter}"
        end
    }
end

if ARGV.length != 4
    puts "Usage: hll-gnuplot-graph <samples> <max> <step> (max|avg|absavg|all)"
    exit 1
end
filter_samples(ARGV[0].to_i,ARGV[1].to_i,ARGV[2].to_i,ARGV[3].to_sym)