Benchmarks

ruby_array_join_vs_string_concatenation.rb

# Array#join vs String#+
require 'benchmark'

n = 1_000_000

Benchmark.bm do |x|
  x.report('Array#join :') {
    n.times { ['this', 'is', 'a', 'test'].join(' ') }
  }
  x.report('String#+ :') {
    n.times { 'this' + ' ' + 'is' + ' ' + 'a' + ' ' + 'test' }
  }
end


# RUBY_VERSION = '1.8.7'
#               user      system    total     real
# Array#join :  3.120000  0.020000  3.140000  (3.568955)
# String#+ :    5.400000  0.050000  5.450000  (6.579634)

# RUBY_VERSION = 'ruby-1.9.3-p194'
#               user       system     total    real
#Array#join :   2.980000   0.020000   3.000000 (3.075411)
#String#+ :     3.290000   0.010000   3.300000 (3.346815)

# ruby -v
# ruby 2.1.1p76 (2014-02-24 revision 45161) [x86_64-darwin12.0]
#        user     system      total        real
# Array#join :  1.270000   0.000000   1.270000 (  1.269124)
# String#+ :  0.880000   0.000000   0.880000 (  0.886282)

updated.rb

require 'benchmark'
 
n = 10_000_000

val1 = 'test'

Benchmark.bm do |x|
  x.report('String#{} :') {
    n.times { "this is a #{val1}" }
  }
  x.report('Array#join :') {
    n.times { ['this is a', val1].join(' ') }
  }
  x.report('String#+ :') {
    n.times { 'this is a ' + val1 }
  }
end

# ruby -v
# ruby 2.1.1p76 (2014-02-24 revision 45161) [x86_64-darwin12.0]

#       user     system      total        real
# String#{} :  1.700000   0.000000   1.700000 (  1.703822)
# Array#join :  6.620000   0.000000   6.620000 (  6.622582)
# String#+ :  1.770000   0.010000   1.780000 (  1.781350)

+1