Array push vs concatenation

gistfile1.rb

Benchmark.bmbm do |x|
  x.report('<<:') do
    arr = []
    50_000.times do |i|
      arr2 = [i]
      arr << arr2
    end
  end

  x.report('+=:') do
    arr = []
    50_000.times do |i|
      arr2 = [i]
      arr += arr2
    end
  end

  x.report('concat:') do
    arr = []
    50_000.times do |i|
      arr2 = [i]
      arr.concat(arr2)
    end
  end
end

# Rehearsal -------------------------------------------
# <<:       0.030000   0.000000   0.030000 (  0.025257)
# +=:       3.260000   2.810000   6.070000 (  6.084500)
# concat:   1.430000   0.000000   1.430000 (  1.429430)
# ---------------------------------- total: 7.530000sec
# 
#               user     system      total        real
# <<:       0.020000   0.000000   0.020000 (  0.017310)
# +=:       3.190000   2.720000   5.910000 (  5.910808)
# concat:   1.390000   0.000000   1.390000 (  1.397712)

# Surprise! Creating 50,000 arrays is slow.