Corrected version

require 'json'
require 'benchmark'
require 'oj'
require 'yajl'

a = {'asdfg'=> 'asdfg', 'qwert'=> 'asdfatqwtrqewt', 'rewqrq'=>543252, 'reqrqwer'=>[143245,1234421]}
j = a.to_json

N = (ARGV[0] || 100000).to_i

Benchmark.bmbm(6) do |x|
  x.report('json g') do N.times{a.to_json } end
  x.report('yajl g') do N.times{Yajl.dump(a)} end
  x.report('oj   g') do N.times{Oj.dump(a)} end
  x.report('ojc  g') do N.times{Oj.dump(a, mode: :compat)} end
  x.report('json p') do N.times{JSON.parse(j)} end
  x.report('yajl p') do N.times{Yajl.load(j)} end
  x.report('oj   g') do N.times{Oj.load(j)} end
  x.report('ojc  g') do N.times{Oj.load(j, mode: :compat)} end
  # Correct use of Oj::Doc
  x.report('ojdocg') do N.times{Oj::Doc.open(j) { |x| x.fetch('asdfg') } } end
end

# results from ruby 1.9.3-p194 on OS X

              user     system      total        real
json g    0.700000   0.010000   0.710000 (  0.706307)
yajl g    0.660000   0.000000   0.660000 (  0.658921)
oj   g    0.490000   0.000000   0.490000 (  0.487269)
ojc  g    0.570000   0.000000   0.570000 (  0.571865)
json p    0.850000   0.000000   0.850000 (  0.851527)
yajl p    0.750000   0.000000   0.750000 (  0.744586)
oj   g    0.350000   0.000000   0.350000 (  0.351567)
ojc  g    0.450000   0.000000   0.450000 (  0.447477)
ojdocg    0.110000   0.000000   0.110000 (  0.114286)