thread_incr.rb

require "thread"

Thread.abort_on_exception = true

def none
  counter = 0

  threads = 10.times.map do
    Thread.new do
      100.times do
        counter += 1
      end
    end
  end

  threads.each(&:join)
  counter
end

def mutex
  counter = 0
  lock    = Mutex.new

  threads = 10.times.map do
    Thread.new do
      100.times do
        lock.synchronize { counter += 1 }
      end
    end
  end

  threads.each(&:join)
  counter
end

def atomic
  require "atomic"
  counter = Atomic.new(0)

  threads = 10.times.map do
    Thread.new do
      100.times do
        counter.update{|v| v + 1}
      end
    end
  end

  threads.each(&:join)
  counter.value
end

require "benchmark"

n = 10
Benchmark.bm(7) do |b|
  b.report("none")   { n.times { none } }
  b.report("mutex")  { n.times {mutex } }
  b.report("atomic") { n.times { atomic } }
end