Ruby 1.8.5 のSHA1 がやたら速いんだが

何故だ。MD5 の方が速いんじゃないの?

ベンチマーク

$ /usr/local/bin/ruby -v hash_bench.rb                                                                            [~/tmp]
ruby 1.8.5 (2006-08-25) [i686-darwin9.5.0]
Rehearsal ----------------------------------------
MD5    4.070000   0.010000   4.080000 (  4.102120)
SHA1   1.580000   0.010000   1.590000 (  1.602017)
------------------------------- total: 5.670000sec

           user     system      total        real
MD5    4.030000   0.020000   4.050000 (  4.083039)
SHA1   1.620000   0.010000   1.630000 (  1.634931)

$ /usr/bin/ruby -v hash_bench.rb                                                                                  [~/tmp]
ruby 1.8.6 (2008-03-03 patchlevel 114) [universal-darwin9.0]
Rehearsal ----------------------------------------
MD5    2.520000   0.010000   2.530000 (  2.557895)
SHA1   3.570000   0.010000   3.580000 (  3.612239)
------------------------------- total: 6.110000sec

           user     system      total        real
MD5    2.530000   0.010000   2.540000 (  2.551385)
SHA1   3.620000   0.020000   3.640000 (  3.683908)

$ /opt/local/bin/ruby -v hash_bench.rb                                                                            [~/tmp]
ruby 1.8.7 (2008-06-20 patchlevel 22) [i686-darwin9]
Rehearsal ----------------------------------------
MD5    4.560000   0.840000   5.400000 (  5.442298)
SHA1   4.970000   0.870000   5.840000 (  5.874196)
------------------------------ total: 11.240000sec

           user     system      total        real
MD5    4.570000   0.840000   5.410000 (  5.439444)
SHA1   4.980000   0.860000   5.840000 (  5.894651)

ソース

require 'benchmark'
require 'digest/sha1'
require 'digest/md5'

n = 10**6

str = 'Ax098UjkG'
Benchmark.bmbm do |x|
  x.report('MD5 '){ n.times{ Digest::MD5.hexdigest(str)}}
  x.report('SHA1'){ n.times{ Digest::SHA1.hexdigest(str)}}
end

追記

16進数の文字列への変換が問題でした。

ベンチマーク

$ /usr/local/bin/ruby -v hash_bench.rb                                                                            [~/tmp]
ruby 1.8.5 (2006-08-25) [i686-darwin9.5.0]
Rehearsal ----------------------------------------
MD5    1.350000   0.010000   1.360000 (  1.378982)
SHA1   1.490000   0.010000   1.500000 (  1.532837)
------------------------------- total: 2.860000sec

           user     system      total        real
MD5    1.310000   0.000000   1.310000 (  1.358399)
SHA1   1.530000   0.010000   1.540000 (  1.547941)

ソース

require 'benchmark'
require 'digest/sha1'
require 'digest/md5'

n = 10**6

str = 'Ax098UjkG'
Benchmark.bmbm do |x|
  x.report('MD5 '){ n.times{ Digest::MD5.digest(str)}}
  x.report('SHA1'){ n.times{ Digest::SHA1.digest(str)}}
end