Re: [Starpu-devel] Why starpu_mpi_barrier waits for all taks ?

[Nathalie Furmento <nathalie.furmento@labri.fr>]

On 14/04/2020 18:23, Samuel Thibault wrote:
> Philippe SWARTVAGHER, le mar. 14 avril 2020 18:02:00 +0200, a ecrit:
>> Why starpu_mpi_barrier waits for all tasks ?
> In the way we were using it (a synchronization in the task graph), it
> has to be so, because MPI requests can make tasks ready, which can make
> MPI requests ready, etc. So for starpu_mpi_wait_for_all, we need that
> behavior.
>
>> Could we consider creating a function starpu_mpi_barrier_unsafe(), calling
>> directly MPI_Barrier ?
> Actually starpu_mpi_barrier itself could have that behavior, just like
> starpu_mpi_send/recv() don't care much about the task graph of the STF
> flow. But we need our current implementation for
> starpu_mpi_wait_for_all.
>
> Put another way, I'd say:
>
> - rename _starpu_mpi_barrier to _starpu_mpi_wait_for_all
> - call _starpu_mpi_wait_for_all from starpu_mpi_wait_for_all
> - create a new _starpu_mpi_barrier which works like you said.


And also make sure to replace where it's relevant, calls to
starpu_mpi_barrier by calls to starpu_mpi_wait_for_all()

Cheers,

Nathalie