simple bench runner to do multiple runs

test/bench/runner.rb

@@ -0,0 +1,41 @@
+require "benchmark"
+class Stats
+
+  def initialize
+    @n = 0
+    @mean = 0.0
+    @variance = 0.0
+  end
+  attr_reader :n , :mean ,  :variance
+
+  def add(x)
+    @n = @n + 1
+    delta = x - @mean
+    @mean = @mean + delta/@n
+    @variance = @variance + delta*(x - @mean)
+  end
+  def show
+    puts "no    per   var"
+    puts "#{@n}    #{@mean}   #{@variance}"
+  end
+end
+class Runner
+  def initialize num = 20
+    @stats = Stats.new
+    @cmd = ARGV[0]
+    @interations = num
+  end
+  def run
+    @interations.times { once }
+    @stats.show
+  end
+
+  def once
+    GC.disable
+    took = Benchmark.measure { %x("#{@cmd}")}.real
+    GC.enable
+    @stats.add took
+  end
+end
+
+Runner.new.run