hll-gnuplot-graph.rb added to plot HyperLogLog error graphs.

utils/hyperloglog/hll-gnuplot-graph.rb

+# 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 step of 1000*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 = []
+    while i < max do
+        step.times {
+            elements = []
+            1000.times {
+                ele = Digest::SHA1.hexdigest(i.to_s+seed.to_s)
+                elements << ele
+                i += 1
+            }
+            r.hlladd('hll',*elements)
+        }
+        approx = r.hllcount('hll')
+        err = approx-i
+        rel_err = 100.to_f*err/i
+        samples << [i,rel_err]
+    end
+    samples
+end
+
+def filter_samples(numsets,filter)
+    r = Redis.new
+    dataset = {}
+    (0...numsets).each{|i|
+        dataset[i] = run_experiment(r,i,100000,1)
+    }
+    dataset[0].each_with_index{|ele,index|
+        card,err=ele
+        if filter == :max
+            (1...numsets).each{|i|
+                err = dataset[i][index][1] if err < dataset[i][index][1]
+            }
+        elsif filter == :avg
+            (1...numsets).each{|i|
+                err += dataset[i][index][1]
+            }
+            err /= numsets
+        else
+            raise "Unknown filter #{filter}"
+        end
+        puts "#{card} #{err}"
+    }
+end
+
+filter_samples(100,:max)
+#filter_samples(100,:avg)