showdist.rb utility for SRANDMEMBER analysis added.

utils/srandmember/README.md

+This utility plots the distribution of SRANDMEMBER to evaluate how fair it is.
+See http://theshfl.com/redis_sets for more information on the topic.

utils/srandmember/showdist.rb

+require 'redis'
+
+r = Redis.new
+r.select(9)
+r.del("myset");
+r.sadd("myset",(0..999).to_a)
+freq = {}
+100.times {
+    res = r.pipelined {
+        1000.times {
+            r.srandmember("myset")
+        }
+    }
+    res.each{|ele|
+        freq[ele] = 0 if freq[ele] == nil
+        freq[ele] += 1
+    }
+}
+
+# Convert into frequency distribution
+dist = {}
+freq.each{|item,count|
+    dist[count] = 0 if dist[count] == nil
+    dist[count] += 1
+}
+
+min = dist.keys.min
+max = dist.keys.max
+(min..max).each{|x|
+    count = dist[x]
+    count = 0 if count == nil
+    puts "#{x} -> #{"*"*count}"
+}