threadsplosion.rb

require "thread"

$mutex = Mutex.new
$total = 0

def incr
  $mutex.synchronize { $total += 1 }
  sleep
end

def total
  $mutex.synchronize { return $total }
end

def fib(n)
  incr if (0..1).include? n
  fib(n-1) + fib(n-2) if n > 1
end

threads = []

1000.times do
  threads << Thread.new { fib(30) }
end

sleep 0.5 until total == 1000

system "ps -orss #{Process.pid}"