* benchmark/driver.rb: Add difference column to report that averages

	  across all runs of a benchmark.  [Ruby 1.9 - Feature ruby#4982]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@32430 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Thu Jul  7 06:46:12 2011  Eric Hodel  <[email protected]>
+
+	* benchmark/driver.rb:  Add difference column to report that averages
+	  across all runs of a benchmark.  [Ruby 1.9 - Feature #4982]
+
 Thu Jul  7 06:19:38 2011  Eric Hodel  <[email protected]>
 
 	* lib/rubygems.rb:  Reduce requires to improve `make benchmark`.

benchmark/driver.rb

@@ -90,6 +90,10 @@ def initialize execs, dir, opt = {}
     end
   end
 
+  def average results
+    results.inject(:+) / results.length
+  end
+
   def show_results
     output
 
@@ -109,7 +113,10 @@ def show_results
       output "minimum results in each #{@repeat} measurements."
     end
 
-    output "name\t#{@execs.map{|(e, v)| v}.join("\t")}"
+    difference = "\taverage difference" if @execs.length == 2
+    total_difference = 0
+
+    output "name\t#{@execs.map{|(e, v)| v}.join("\t")}#{difference}"
     @results.each{|v, result|
       rets = []
       s = nil
@@ -129,8 +136,20 @@ def show_results
         end
         rets << sprintf("%.3f", r)
       }
+
+      if difference
+        diff = average(result.last) - average(result.first)
+        total_difference += diff
+        rets << sprintf("%.3f", diff)
+      end
+
       output "#{v}#{s}\t#{rets.join("\t")}"
     }
+
+    if difference and @verbose
+      output '-----------------------------------------------------------'
+      output "average total difference is #{total_difference}"
+    end
   end
 
   def files