Benchmark concatenating strings with reduce(:+) vs. with join('').

gistfile1.rb

require 'benchmark'

STRING = 'abc'
ITERATIONS = 500000

Benchmark.bm(10) do |bench|
  for n in [2,3,4, 5]
    n_strings = Array.new(n, STRING)

    bench.report("add  #{n}") do
      ITERATIONS.times do
        n_strings.reduce(:+)
      end
    end

    bench.report("join #{n}") do
      ITERATIONS.times do
        tmp = n_strings.join('')
      end
    end

    iteratable_dups = (0...ITERATIONS).map { n_strings.map(&:dup) }
    bench.report("append #{n}") do
      iteratable_dups.each do |dups|
        dups.reduce(:<<)
      end
    end

    puts "\n"
  end
end

ruby 1.9.3p125 (2012-02-16 revision 34643) [x86_64-darwin10.8.0]

add  2       0.280000   0.000000   0.280000 (  0.280966)
join 2       0.390000   0.000000   0.390000 (  0.390578)
append 2     0.340000   0.010000   0.350000 (  0.379686)

add  3       0.590000   0.010000   0.600000 (  0.637222)
join 3       1.130000   0.050000   1.180000 (  1.201451)
append 3     0.350000   0.020000   0.370000 (  0.376768)

add  4       0.480000   0.070000   0.550000 (  0.571988)
join 4       1.190000   0.030000   1.220000 (  1.265706)
append 4     0.420000   0.000000   0.420000 (  0.422308)

add  5       0.630000   0.000000   0.630000 (  0.638082)
join 5       1.520000   0.060000   1.580000 (  1.597781)
append 5     0.530000   0.010000   0.540000 (  0.546513)