[mpich-devel] call PMI before MPI_Init_thread?

[Balaji, Pavan]

It works in the implementation, so I’m not sure what you mean.  I just mean it’s not allowed per the “spec” (or whatever sparse documentation we have that others use for implementing PMI).

  — Pavan

> On Apr 24, 2015, at 7:22 AM, Jeff Hammond <jeff.science at gmail.com> wrote:
> 
> Why not implement the equivalent of the ref-counting init proposal or
> at least the simple things that allows multiple inits but only one
> finalize?  Is it that you don't see the effort being worthwhile or
> because there is a principled reason (PMI semantics should match MPI)?
> 
> Given that e.g. PGAS runtimes may want to use PMI for bootstrapping (I
> do this with DMAPP code on Cray, for example), it seems to benefit
> user experience to support this behavior.
> 
> Thanks,
> 
> Jeff
> 
> On Fri, Apr 24, 2015 at 1:12 AM, Balaji, Pavan <balaji at anl.gov> wrote:
>> 
>> Multiple PMI Inits are not allowed.  It might work in the current
>> implementation within MPICH, but is not safe.
>> 
>> If you are looking for MPICH specific behavior, you can look for the PMI_ID
>> and PMI_RANK environment variables instead to get your rank.
>> 
>>  — Pavan
>> 
>> On Apr 21, 2015, at 11:17 PM, Jeff Hammond <jeff.science at gmail.com> wrote:
>> 
>> So MPICH doesn't fail when I try this on my Mac, but it would be good
>> to know if I have a reasonable expectation of doing this in general.
>> 
>> Thanks,
>> 
>> Jeff
>> 
>> jrhammon-mac01:ENDPOINTS jrhammon$ mpiexec -n 4 ./a.out
>> PMI says I am 2 of 4
>> PMI says I am 0 of 4
>> PMI says I am 1 of 4
>> PMI says I am 3 of 4
>> MPI says I am 0 of 4 (provided=1)
>> MPI says I am 2 of 4 (provided=1)
>> MPI says I am 3 of 4 (provided=3)
>> MPI says I am 1 of 4 (provided=3)
>> 
>> jrhammon-mac01:ENDPOINTS jrhammon$ cat pmi.c
>> #include <stdio.h>
>> #include <stdlib.h>
>> 
>> /*#include <pmi.h>*/
>> int PMI_Init( int *spawned );
>> int PMI_Finalize( void );
>> int PMI_Get_size( int *size );
>> int PMI_Get_rank( int *rank );
>> 
>> #include <mpi.h>
>> 
>> int main(int argc, char * argv[])
>> {
>>   int has_parent;
>>   PMI_Init(&has_parent);
>> 
>>   int rank, size;
>>   PMI_Get_size(&size);
>>   PMI_Get_rank(&rank);
>> 
>>   printf("PMI says I am %d of %d \n", rank, size);
>>   fflush(stdout);
>> 
>>   int requested = (rank%2==0) ? MPI_THREAD_FUNNELED : MPI_THREAD_MULTIPLE;
>>   int provided;
>>   MPI_Init_thread(&argc, &argv, requested, &provided);
>> 
>>   int wsize, wrank;
>>   MPI_Comm_size(MPI_COMM_WORLD, &wsize);
>>   MPI_Comm_rank(MPI_COMM_WORLD, &wrank);
>> 
>>   printf("MPI says I am %d of %d (provided=%d)\n", wrank, wsize, provided);
>>   fflush(stdout);
>> 
>>   MPI_Finalize();
>>   //PMI_Finalize(); /* required? */
>> 
>>   return 0;
>> }
>> 
>> On Tue, Apr 21, 2015 at 9:09 PM, Jeff Hammond <jeff.science at gmail.com>
>> wrote:
>> 
>> Is it valid in _MPICH_ to make calls to PMI before MPI is initialized?
>> I am interested in PMI_Init, PMI_Get_size and PMI_Get_rank.
>> 
>> The motivating use case is to initialize e.g. half my ranks with
>> MPI_THREAD_FUNNELED and the other half with MPI_THREAD_MULTIPLE but
>> not use MPMD launching.
>> 
>> I have two reasons for wanting to do it this way.  First, it is
>> otherwise unnecessary to use MPMD since I can branch at the top of my
>> code and meet the requirements of FUNNELED and MULTIPLE.  Second, I
>> might be interested in running my code on a supercomputer with an
>> MPICH-based MPI implementation that does not support MPMD launching in
>> an unrestricted manner.
>> 
>> If MPICH can handle this, then I will worry about whether or not the
>> aforementioned supercomputer can.  It is my assumption that, if MPICH
>> cannot handle this, then the MPICH derivative in question cannot
>> either.
>> 
>> Thanks,
>> 
>> Jeff
>> 
>> --
>> Jeff Hammond
>> jeff.science at gmail.com
>> http://jeffhammond.github.io/
>> 
>> 
>> 
>> 
>> --
>> Jeff Hammond
>> jeff.science at gmail.com
>> http://jeffhammond.github.io/
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> 
> 
> -- 
> Jeff Hammond
> jeff.science at gmail.com
> http://jeffhammond.github.io/
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