Have fun with benchmarking in Ruby

benchmark.rb

require 'benchmark'

@i=0

def undefined_check
  return @undefined_check += 2 if defined?(@undefined_check)
  return @i += 1
end

@nil = nil
def nil_check
  return @nil += 2 unless @nil.nil?
  return @i += 1
end

@defined_nil = nil
def defined_nil_check
  return @defined_nil += 2 unless defined?(@defined_nil)
  return @i += 1
end

@defined = 'defined'
def defined_check
  return @defined += 2 unless defined?(@defined)
  return @i += 1
end

def no_defined_check
  return @i += 1
end

def exception_check
  begin
    return @undefined += 1
  rescue Exception => _
    return @i += 1
  end
end

n=1600000
Benchmark.bm(25) do |benchmark|
  @i=0
  benchmark.report("undefined_check") do
    n.times { undefined_check }
  end

  @i=0
  benchmark.report("nil_check") do
    n.times { nil_check }
  end

  @i=0
  benchmark.report("defined_nil_check") do
    n.times { defined_nil_check }
  end

  @i=0
  benchmark.report("defined_check") do
    n.times { defined_check }
  end

  @i=0
  benchmark.report("no_defined_check") do
    n.times { no_defined_check }
  end

  @i=0
  benchmark.report("exception_check") do
    n.times { exception_check }
  end
end


#                                user     system      total        real
#undefined_check             0.200000   0.000000   0.200000 (  0.194759)
#nil_check                   0.170000   0.000000   0.170000 (  0.176591)
#defined_nil_check           0.200000   0.000000   0.200000 (  0.196691)
#defined_check               0.210000   0.000000   0.210000 (  0.209552)
#no_defined_check            0.140000   0.000000   0.140000 (  0.140443)
#exception_check             4.770000   0.010000   4.780000 (  4.782087)