help?> OhMyThreads.Experimental.@barrier
  @barrier


  This can be used inside a @tasks for ... end to synchronize n parallel tasks.
  Specifically, a task can only pass the @barrier if n-1 other tasks have reached it
  as well. The value of n is determined from @set ntasks=..., which is required if one
  wants to use @barrier.

  Because this feature is experimental, it is required to load @barrier explicitly,
  e.g. via using OhMyThreads.Experimental: @barrier.

  WARNING: It is the responsibility of the user to ensure that the right number of
  tasks actually reach the barrier. Otherwise, a deadlock can occur. In partictular,
  if the number of iterations is not a multiple of n, the last few iterations
  (remainder) will be run by less than n tasks which will never be able to pass a
  @barrier.

  Example
  =======

  using OhMyThreads: @tasks
  
  # works
  @tasks for i in 1:20
      @set ntasks = 20
  
      sleep(i * 0.2)
      println(i, ": before")
      @barrier
      println(i, ": after")
  end
  
  # wrong - deadlock!
  @tasks for i in 1:22 # ntasks % niterations != 0
      @set ntasks = 20
  
      println(i, ": before")
      @barrier
      println(i, ": after")
  end