Compare [].join to string interpolation

benchmark.rb

# Ruby 1.9.3-p125
require 'benchmark'

variable = 'string'
integer = 5

n = 1_000_000

Benchmark.bm do |x|
  x.report("array:") do
    n.times do
      [:part, variable, integer].join(':')
    end
  end
  x.report("string:") do
    n.times do
      "#{:part}:#{variable}:#{integer}"
    end
  end
end

results.txt

# Ruby 1.9.2-p290
# n = 1_000_000
           user     system      total        real
array:   1.330000   0.000000   1.330000 (  1.327477)
string:  0.790000   0.000000   0.790000 (  0.794048)

# Ruby 1.9.2-p290
# n = 10_000_000
           user     system      total        real
array:   12.950000   0.010000  12.960000 ( 12.950889)
string:   7.850000   0.020000   7.870000 (  7.862994)

# Ruby 1.9.3-p0
# n = 10_000_000
          user     system      total        real
array:  13.230000   0.010000  13.240000 ( 13.235264)
string:  7.900000   0.010000   7.910000 (  7.906731)

# Ruby 1.9.3-p125
# n = 10_000_000
           user     system      total        real
array:  13.270000   0.000000  13.270000 ( 13.277366)
string:  8.190000   0.000000   8.190000 (  8.190424)

# Ruby 1.9.3-p125 falcon patch (https://gist.github.com/1688857)
# n = 10_000_000
         user     system      total        real
array 33.470000   0.010000  33.480000 ( 33.485981)
str1  31.130000   0.000000  31.130000 ( 31.132234)
str2  31.570000   0.010000  31.580000 ( 31.589953)