Re: [mpi-21] ABI: feature categories

["William Yu" <wyu@xxxxxxxxxx>]

I think we just have to standardize the behavior of things like mpirun and mpiexec such as what cwd does it use by default, order of loading arguments in the system and others. Other items like process loading order could probably also matter.

However, i have not been exposed to many mpi implementations that have non-uniform implementations of mpirun and mpiexec to comment enough on this.


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Subject:	Re: [mpi-21] ABI: feature categories
Author:	Greg Bronevetsky <bronevetsky1@xxxxxxxx>
Date:		January 13th 2008 10:21 pm

To me its clear that standardizing mpistart, 
stdout/stderr/stdin and environment variables 
will provide large usability gains without much 
of a cost to MPI implementors (correct me if I'm 
wrong). Interactions between MPI and the batch 
scheduler seem to be difficult to standardize. 
How are people handling this now? Can somebody 
explain the issues with stack sizes, MPI I/O and 
CWD? I'm not familiar with these.

Greg Bronevetsky
Post-Doctoral Researcher
1028 Building 451
Lawrence Livermore National Lab
(925) 424-5756
bronevetsky1@xxxxxxxx

At 02:10 PM 1/13/2008, Greg Bronevetsky wrote:
>To clarify the debate surrounding the ABI 
>proposal I've gone through Greg Lindahl's talk 
>and broken the main points of the talk down into the following categories:
>         User-MPI interactions
>         Application-MPI interactions
>         System-MPI interactions
>As we've discussed, about morph layers address 
>all the points under the "Application-MPI 
>interactions" category. In other words, if we 
>used morph layers we wouldn't need to 
>standardize things like mpi.h. What's left are 
>the User-MPI and System-MPI interactions. The 
>question that I would like to put forward is: 
>How useful are these? Most of the discussion 
>I've heard recently focuses on Application-MPI 
>interactions. If we can table this for the time 
>being until morph layers can be evaluated, is 
>there enough support to proceed with the rest of 
>the proposal or is the Application-MPI 
>interactions the core part? Please speak up.
>
>User-MPI interactions
>         ?mpistart? -- ?mpirun? with standard args
>                 Start over: ?mpistart? with standardized args
>                 Require features such as 
> supporting pipes of stdin, stdout, error
>                 --batch and ­batch-wait to 
> assist scripting in the presense of batch queues... noop if no queue sys
>Application-MPI interactions
>         Fully specify what's in <mpi.h> and ?mpif.h?
>                 Variably-sized items have to be nailed down
>                 MPI_Status must have fixed length
>         Need a sane shared-library setup to avoid relinking
>                 I think this means we need 1 
> base library instead of the usual chaos
>                 Implementers can dlopen() additional libs as needed
>                 Perhaps we can have a clever 
> upward-compatible scheme for MPI 1 and MPI 2 libs
>System-MPI interactions
>         Fully specify startup and queue system interaction in a flexible way
>                 Queue sys handles creation of MPI processes
>                 Standard command-line for MPI 
> process, with enough info to connect to the ? job?
>                 MPI implementation provides ? job? process; all
>                 MPI processes contact to coordinate.
>                         ? job? process started by mpistart
>                 Queue sys ensures all MPI processes exit at end.
>                 I think this supports all 
> existing queue systems and MPI implementations
>         Specify environmental items so that most apps are portable
>                 Getenv / putenv: most 
> implementations don't propagate env vars to 
> ranks 1+; few support using putenv to other processes.
>                 Cwd depends on batch system and sysadmin
>                         2 choices: least common denominator, or query fns?
>                 Stack size. Usually painful for users to fix.
>                 stdin/stdout/stderr... oh, don't forget buffering...
>                 MPI-I/O.
>                 Actions before/after mpi_init/finalize
>
>Greg Bronevetsky
>Post-Doctoral Researcher
>1028 Building 451
>Lawrence Livermore National Lab
>(925) 424-5756
>bronevetsky1@xxxxxxxx