[Openmp-dev] Implementation of nowait and async in libomptarget

[Johannes Doerfert via Openmp-dev]

Hi Manoel,

Shilei (CC'ed) has a proper implementation of target nowait, for now we 
basically implement it synchronously.

The reviews are online and Shilei will share the links. Feel free to 
join our weekly meeting [1] to as we discuss it there as well.

~ Johannes

[1] 
https://docs.google.com/document/d/1Tz8WFN13n7yJ-SCE0Qjqf9LmjGUw0dWO9Ts1ss4YOdg/edit?usp=sharing


On 9/14/20 3:03 PM, Römmer, Manoel via Openmp-dev wrote:
> Hi everyone,
>
> I'm looking into the use of `nowait` with target regions and I have some questions about the implementation in libomptarget, maybe someone here can help me with some details.
>
> Libomptarget has an optional async interface, for plugins to implement. I orignally expected, that nowait target regions would be implemented with a call to __tgt_run_target_region_async(), but the implementation in libomptarget seems to always use the async interface when available (even for blocking target region executions) and always tries to synchronize after a target region is executed.
>
> Can someone tell me if I got this right and how a `#pragma omp target nowait` is handled by the openmp runtime?
>
>
> Thanks,
>
> Manoel Römmer
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