Smartphores.jl provides the standard semaphores machinery with the sole distinction that smartphores provide ids to available slots. This can be helpful if one has allocated $n$ chunks of memory that are to be shared, so a call to acquire then returns an integer value that indicates which chunk is assigned, which should be released using release.

There are only three calls:

Smartphore( size :: Int ) creates

acquire( s :: Smartphore ) acquires a permit and returns its id

release( s :: Smartphore, permitid :: Int ) releases the permit

All of this is a mild hack of the standard Julia Semaphore machinery found in lock.jl. The same MIT license applies.

Here is a simple example to demonstrate:

using Smartphores

function howthisworks( n )
    blocks = [ zeros(5) for i ∈ 1:n ]
    
    s = Smartphore( n )
    Threads.@threads for i ∈ 1 : 20
        local a = acquire( s )
        println( "thread $(Threads.threadid()) says: block $a is mine, all mine" )
        blocks[a] .= i
        println( "thread $(Threads.threadid()) says: I'm giving block $a back" )
        release( s, a )
    end
    for a ∈ 1:n
        println( blocks[a] )
    end
end

howthisworks( 3 )