ruby/ruby — pull request #722 by wojtekmach (2014-09-17 22:05:13+00:00)
Title: Replace map/flatten with flat_map

flat_map is faster and uses less object allocations.
See my bench setup & results: https://gist.github.com/wojtekmach/925a780b844dc1d7114a

Thanks to @sferik for a presentation on speeding up ruby: https://speakerdeck.com/sferik/writing-fast-ruby