http://twitter.com/#!/mfeathers/status/119386996354449408

reverse sort speed

>> x = (1..10000000).to_a; x.length
=> 10000000
>> 
?> by_reverse = Proc.new{|p,o| Proc.new{|a,b| b.send(p,o) <=> a.send(p,o)}}
=> #<Proc:0x000000013b68a330@(irb):50>
>>  Benchmark.bm do |y|
?>  y.report("sort_by neg") { x.sort_by{|i| - (i + 1)} }
>>  y.report("sort no_send") { x.sort{|a,b| (b + 1) <=> (a + 1)} }
>>  y.report("sort send") { x.sort{|a,b| b.send('+', 1) <=> a.send('+', 1)}}
>>  y.report('procs send') {  x.sort(&(by_reverse.call('+',1))) }
>>  y.report('sort_by send reverse') { x.sort_by{|i| i.send('+', 1)}.reverse}
>>  y.report('sort_by reverse') { x.sort_by{|i| (i + 1)}.reverse }
>> end

      user     system      total        real
sort_by neg  6.140000   0.030000   6.170000 (  6.169397)
sort no_send  8.500000   0.040000   8.540000 (  8.533514)
sort send 11.880000   0.040000  11.920000 ( 11.930224)
procs send 11.080000   0.040000  11.120000 ( 11.115269)
sort_by send reverse  7.590000   0.020000   7.610000 (  7.607284)
sort_by reverse  5.410000   0.030000   5.440000 (  5.441332)
=> true
>>