Experimental

@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