2.3.1 :001 > require 'benchmark/ips'
LoadError: cannot load such file -- benchmark/ips/stats/sd
from /Users/tneems/.rvm/rubies/ruby-2.3.1/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /Users/tneems/.rvm/rubies/ruby-2.3.1/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require'
from /Users/tneems/.rvm/gems/ruby-2.3.1/gems/benchmark-ips-2.7.0/lib/benchmark/ips.rb:4:in `<top (required)>'
from /Users/tneems/.rvm/rubies/ruby-2.3.1/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:133:in `require'
from /Users/tneems/.rvm/rubies/ruby-2.3.1/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:133:in `rescue in require'
from /Users/tneems/.rvm/rubies/ruby-2.3.1/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:40:in `require'
from (irb):1
from /Users/tneems/.rvm/rubies/ruby-2.3.1/bin/irb:11:in `<main>'