Right now MacRuby is really quite slow for string operations, I noticed it a while back when doing large amounts of string creation, characters swapping, and pushing/popping strings into/out of a priority queue. The attached file is a string performance test and here is a run on my 15" Core i7 MBP with ruby 1.9.1, jruby, and MacRuby: Name ruby 1.9.1p378 MacRuby version jruby 1.5.0.RC1 -------------------------------------------------------------------------------- array:<< 0.751082 1.168693 1.290000 array:new 0.394997 1.917601 0.277000 array:[] 0.324454 0.755054 0.472000 array:[]= 1.691840 0.765225 0.822000 hash:new 1.501595 4.563549 0.444000 hash:[] 0.612701 1.051502 0.589000 hash:[]= 2.012367 1.135856 0.902000 ivar:get 0.215424 0.344873 1.087000 ivar:set 1.349466 0.243909 1.902000 ivar:attr_writer 1.245894 4.587488 0.655000 ivar:attr_reader 1.045779 2.755303 0.482000 loop:upto 1.211598 5.215169 0.874000 loop:times 1.210781 5.215054 0.876000 loop:while 0.599330 0.157019 0.937000 loop:for 1.442154 0.811875 1.132000 method:args 0.728248 0.682097 1.434000 method:noarg 0.822463 0.578383 0.837000 method:splat 0.478610 1.805760 0.227000 method:empty 0.807405 0.527851 1.062000 method:opt 1.027146 2.579715 0.944000 misc:ao_bench 7.838053 8.529954 3.248000 misc:sudoku 1.740196 2.172581 2.461000 misc:tak 1.277399 0.155534 1.563000 misc:mandelbrot 2.956319 0.124588 0.854000 misc:fib 3.827194 0.574900 4.935000 misc:ack 1.049100 0.116299 1.217000 proc:call+splat 0.318346 1.119665 0.191000 proc:call+args 2.477112 1.100848 2.995000 proc:call+noarg 2.496278 1.071953 3.507000 string:store swap 0.153784 0.479202 0.033000 string:<< 0.481788 143.615735 0.099000 string:new 0.276954 1.574715 0.207000 string:[] 0.428182 1.899233 0.072000 string:tuple swap 0.181318 0.721778 0.045000 yield:noarg 0.783281 0.720254 1.269000 yield:splat 0.159219 0.965713 0.094000 yield:less_arity 0.192418 0.843867 0.345000 yield:same_arity 0.937823 0.763344 1.547000 yield:more_arity 0.192516 0.848179 0.421000 Jordan