benchmark string concat vs append vs +

benchmark_string_concat_append_+.rb

require 'benchmark/ips'

n = 100_000

Benchmark.ips do |x|
  x.config(time: 5, warmup: 2)

  x.report('concat') do |times|
    foo = ""

    n.times do |i|
      foo.concat("#{i}")
    end
  end

  x.report('append') do |times|
    foo = ""

    n.times do |i|
      foo << "#{i}"
    end
  end

  x.report('+') do |times|
    foo = ""

    n.times do |i|
      foo += "#{i}"
    end
  end

  x.compare!
end

Warming up --------------------------------------
              concat     2.000  i/100ms
              append     2.000  i/100ms
                   +     1.000  i/100ms
Calculating -------------------------------------
              concat     54.165  (± 7.4%) i/s -    270.000 
              append     54.400  (± 5.5%) i/s -    272.000 
                   +      0.097  (± 0.0%) i/s -      1.000  in  10.351940s

Comparison:
              append:       54.4 i/s
              concat:       54.2 i/s - same-ish: difference falls within error
                   +:        0.1 i/s - 563.15x slower

Darwin mt-4.local 15.4.0 Darwin Kernel Version 15.4.0: Fri Feb 26 22:08:05 PST 2016; root:xnu-3248.40.184~3/RELEASE_X86_64 x86_64