Different ways to build a 100MB string

string-benchmark.rb

require 'benchmark'
require 'stringio'

Benchmark.measure do
  string = ''
  100_000_000.times do
    string << '0'
  end
end
# =>  17.530000   0.040000  17.570000 ( 17.794845)

Benchmark.measure do
  array = []
  100_000_000.times do
    array << '0'
  end
  array.join
end
# =>  62.730000   1.410000  64.140000 ( 64.138629)

Benchmark.measure do
  io = StringIO.new
  100_000_000.times do
    io.write '0'
  end
  io.rewind
  io.read
end
# => 167.350000   2.020000 169.370000 (169.494641)