reduce_bench.rb

require 'benchmark'

Benchmark.bmbm do |x|
  x.report(' 10000 times << e ') do
    (1..10000).reduce([]) { |m,e| m << e }
  end
  x.report(' 10000 times + [e]') do
    (1..10000).reduce([]) { |m,e| m + [e] }
  end
  x.report('100000 times << e ') do
    (1..100000).reduce([]) { |m,e| m << e }
  end
  x.report('100000 times + [e]') do
    (1..100000).reduce([]) { |m,e| m + [e] }
  end
end

__END__

Rehearsal ------------------------------------------------------
 10000 times << e    0.000000   0.000000   0.000000 (  0.002595)
 10000 times + [e]   0.160000   0.060000   0.220000 (  0.217014)
100000 times << e    0.020000   0.000000   0.020000 (  0.024962)
100000 times + [e]  18.610000   4.610000  23.220000 ( 23.347206)
-------------------------------------------- total: 23.460000sec

                         user     system      total        real
 10000 times << e    0.000000   0.000000   0.000000 (  0.002796)
 10000 times + [e]   0.150000   0.060000   0.210000 (  0.209745)
100000 times << e    0.020000   0.000000   0.020000 (  0.019664)
100000 times + [e]  18.540000   4.610000  23.150000 ( 23.283475)