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Subject: Re: [OMPI users] How "CUDA Init prior to MPI_Init" co-exists with unique GPU for each MPI process?
From: Matthieu Brucher (matthieu.brucher_at_[hidden])
Date: 2011-12-14 10:47:05


Processes are not spawned by MPI_Init. They are spawned before by some
applications between your mpirun call and when your program starts. When it
does, you already have all MPI processes (you can check by adding a sleep
or something like that), but they are not synchronized and do not know each
other. This is what MPI_Init is used for.

Matthieu Brucher

2011/12/14 Dmitry N. Mikushin <maemarcus_at_[hidden]>

> Dear colleagues,
> For GPU Winter School powered by Moscow State University cluster
> "Lomonosov", the OpenMPI 1.7 was built to test and popularize CUDA
> capabilities of MPI. There is one strange warning I cannot understand:
> OpenMPI runtime suggests to initialize CUDA prior to MPI_Init. Sorry,
> but how could it be? I thought processes are spawned during MPI_Init,
> and such context will be created on the very first root process. Why
> do we need existing CUDA context before MPI_Init? I think there was no
> such error in previous versions.
> Thanks,
> - D.
> _______________________________________________
> users mailing list
> users_at_[hidden]

Information System Engineer, Ph.D.