string interpolation vs array join

gistfile1.txt

require "benchmark"

puts %x{ruby -v} + "\n"

Benchmark.bmbm do |x|

  N = 1_000_000

  a = "aa"
  b = "bb"
  c = "cc"

  x.report 'string interpolation' do
    N.times {"#{a}-#{b}-#{c}"}
  end
  x.report 'array joining' do
    N.times {[a, b, c].join("-")}
  end
end

print "\n"

jruby 1.6.3 (ruby-1.8.7-p330) (2011-07-07 965162f) (Java HotSpot(TM) 64-Bit Server VM 1.6.0_26) [darwin-x86_64-java]

Rehearsal --------------------------------------------------------
string interpolation   0.331000   0.000000   0.331000 (  0.331000)
array joining          0.352000   0.000000   0.352000 (  0.352000)
----------------------------------------------- total: 0.683000sec

                           user     system      total        real
string interpolation   0.287000   0.000000   0.287000 (  0.287000)
array joining          0.351000   0.000000   0.351000 (  0.351000)

rubinius 1.2.5dev (1.8.7 9335027b yyyy-mm-dd JI) [x86_64-apple-darwin11.0.0]

Rehearsal --------------------------------------------------------
string interpolation   0.276763   0.008056   0.284819 (  0.283093)
array joining          2.530047   0.008351   2.538398 (  2.452822)
----------------------------------------------- total: 2.823217sec

                           user     system      total        real
string interpolation   0.210928   0.000407   0.211335 (  0.211379)
array joining          1.902922   0.003008   1.905930 (  1.906076)

ruby 1.8.7 (2011-02-18 patchlevel 334) [i686-darwin11.0.0], MBARI 0x6770, Ruby Enterprise Edition 2011.03

Rehearsal --------------------------------------------------------
string interpolation   1.200000   0.000000   1.200000 (  1.201270)
array joining          1.310000   0.000000   1.310000 (  1.320347)
----------------------------------------------- total: 2.510000sec

                           user     system      total        real
string interpolation   1.200000   0.000000   1.200000 (  1.205013)
array joining          1.290000   0.000000   1.290000 (  1.282182)

ruby 1.8.6 (2010-09-02 patchlevel 420) [i686-darwin11.1.0]

Rehearsal --------------------------------------------------------
string interpolation   1.080000   0.000000   1.080000 (  1.080896)
array joining          1.050000   0.000000   1.050000 (  1.051609)
----------------------------------------------- total: 2.130000sec

                           user     system      total        real
string interpolation   1.060000   0.000000   1.060000 (  1.058468)
array joining          1.150000   0.000000   1.150000 (  1.183906)

ruby 1.8.7 (2011-06-30 patchlevel 352) [i686-darwin11.0.0]

Rehearsal --------------------------------------------------------
string interpolation   1.180000   0.010000   1.190000 (  1.239572)
array joining          1.180000   0.000000   1.180000 (  1.189541)
----------------------------------------------- total: 2.370000sec

                           user     system      total        real
string interpolation   1.140000   0.000000   1.140000 (  1.138641)
array joining          1.180000   0.000000   1.180000 (  1.193472)

ruby 1.9.2p290 (2011-07-09 revision 32553) [x86_64-darwin11.0.0]

Rehearsal --------------------------------------------------------
string interpolation   0.820000   0.000000   0.820000 (  0.918609)
array joining          1.060000   0.010000   1.070000 (  1.066198)
----------------------------------------------- total: 1.890000sec

                           user     system      total        real
string interpolation   0.830000   0.000000   0.830000 (  0.849953)
array joining          1.160000   0.000000   1.160000 (  1.195687)

ruby 1.9.2p290 (2011-07-09 revision 32553) [x86_64-darwin11.0.0]

Rehearsal --------------------------------------------------------
string interpolation   0.840000   0.010000   0.850000 (  0.924422)
array joining          1.100000   0.000000   1.100000 (  1.126441)
----------------------------------------------- total: 1.950000sec

                           user     system      total        real
string interpolation   0.810000   0.000000   0.810000 (  0.820044)
array joining          1.140000   0.010000   1.150000 (  1.285240)

ruby 1.9.3dev (2011-07-31 revision 32789) [x86_64-darwin11.0.0]

Rehearsal --------------------------------------------------------
string interpolation   0.850000   0.000000   0.850000 (  0.878875)
array joining          1.200000   0.010000   1.210000 (  1.287827)
----------------------------------------------- total: 2.060000sec

                           user     system      total        real
string interpolation   0.830000   0.000000   0.830000 (  0.838500)
array joining          1.190000   0.020000   1.210000 (  1.244710)