[mpiwg-tools] Questions on MPI_T_init_thread

Schulz, Martin schulzm at llnl.gov
Mon Oct 14 23:39:11 CDT 2013

Hi Junchao,

On Oct 14, 2013, at 3:46 PM, Junchao Zhang <jczhang at mcs.anl.gov>

> Hello,
>   I have some questions on MPI_T_init_thread, which are unclear in the Standard.
>  1) Must MPI_T_init_thread() be called in programs before using MPI_T?


>  2) Must MPI_T_init_thread() be only called by the main thread?

No, I don't think we ever limited that (to allow tools running in other threads).

>  3) Is it wrong to do
>      MPI_T_init_thread(MPI_THREAD_SINGLE, &provided);
>      MPI_Init_thread(LEVEL_HIGHER_THAN_SINGLE, &provided);
>     or vice versa,
>      MPI_Init_thread(MPI_THREAD_SINGLE, &provided);
>      MPI_T_init_thread(LEVEL_HIGHER_THAN_SINGLE, &provided);

No, that should be OK - however, an MPI implementation can choose to return SINGLE from the second calls. Perhaps not the best implementation, but a correct one.


>     Thanks.
> --Junchao Zhang
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Martin Schulz, schulzm at llnl.gov, http://people.llnl.gov/schulzm
CASC @ Lawrence Livermore National Laboratory, Livermore, USA

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