[Mpi3-ft] list of opaque objects and othe rmpi entities on the list

Adam T. Moody moody20 at llnl.gov
Thu Dec 6 18:52:50 CST 2012

The goal of this task seems a bit ill-defined to me.  I think it'd be 
good to select one object type, have one person work through a draft, 
send it to the list, and then review that as a group to have a template 
of how to handle the remaining objects.

Also, my guess is that we'll generally end up saying that any MPI object 
may be invalid after any failure, in fact even failures outside the 
scope of the user's MPI processes.  This can be true for objects that 
are generally thought of being "local" to the MPI rank, such as 
information contained in an info object.  For example, there is nothing 
preventing an MPI implementation from storing the contents of an info 
object on a remote node, such that simple key/value queries may not work 
after this node has failed.  In fact you might have cases where all 
ranks can talk with one another just fine, but one particular rank can't 
read its info objects.

At very large scales, certain objects like groups will have to be stored 
in a distributed manner, so that a call to inquire group information 
will have to access memory on a remote node which may have failed.  Thus 
even a "local MPI call" like MPI_GROUP_TRANSLATE_RANKS might suddently 
start to return errors when it didn't before.

Howard Pritchard wrote:

>Hi Folks,
>Here's the list of mpi opaque objects and a few additional constructs for
>consideration of states in the presence of process failures:
>communicators - Aourelian, Wesley
>groups -  Rich G.
>data types - Sayantan
>RMA windows - Howard
>files (file handles) - Darius B.
>info object  - Darius
>error handler - Darius
>message obj. - David S.
>request - Manjo
>status - Manjo
>op  - Darius
>port (mpi-2 dynamic) - David S.
>user buffers attached to MPI for bsends - Sayantan
>Need to define lifecycle of the object in the case of no process failures,
>and in the case when one or more process failures occur while the
>object exists.
>mpi3-ft mailing list
>mpi3-ft at lists.mpi-forum.org

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