To make this friendly and not too verbose to repl usage, a minimal show method for Vector{IdDict{Any, Any}} could be added

I think there is already a different macro for parallel reductions that can be more efficient than this (parallel reductions)? I forget what the name changed to. It used to be @parallel in v0.0.

@vtjnash are you thinking of what's now @distributed [reducer] for ...? We've never had something like that for multithreading in Base, only multiprocessing as far as I'm aware.

Yeah, sounds right

I think the right strategy here is to implement something akin to Hyper Reducers in Cilk (http://www.fftw.org/~athena/papers/hyper.pdf)

@tkf was experimenting with similar constructs, and I think it would be worthwhile providing a richer infrastructure in Base,
but I don't think returning/exposing TLS is the right strategy.

Another idea would be to expose a way to handle the buffer objects without the user having to manipulate tasks/TLSs

xs, ys = Threads.@threads x = zeros(10,10) y = zeros(2,2) for i in eachindex(a)
 	# do something with x, y, a[i] etc.
end

# optionally do something with xs & ys which are both of length threadpoolsize()

Edit: tried out here #50052

I would prefer that over exposing the TLS objects in that way. Kinda reminds me of Floops reducers.

I am not super convinced by the syntax, but the common ask seems to be that one wants some buffer shared by iterations on that tasks and then somehow returned.

How about having the local keyword create a task-local variable?

Edit: Or some new Julia keyword task_local akin to thread_local from C++.

https://en.cppreference.com/w/cpp/language/storage_duration

What would an example of that look like? I think I get idea but not sure how initialization would be indicated

It seems to me that using task_local_storage() with @threads (and returning tls in some form from the macro) would rarely be a good fit because task_local_storage() access has to be in the loop body, thus you introduce dict operations every iteration.

#50052 seems like a better fit for @threads use cases.

I'm tempted to close this in favor of that

What would an example of that look like? I think I get idea but not sure how initialization would be indicated

Threads.@threads for i in eachindex(a)
    # only initialized once; not reset between different `i`
    # similar to `static` from C/C++
    local x = zeros(10, 10)
    local y = zeros(2, 2)

    # do something with x, y, a[i] etc.
end