[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:
>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
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>mpi3-ft at lists.mpi-forum.org
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