[Mpi3-subsetting] agenda for subsetting kickoff telecon ww09

[Supalov, Alexander]

Hi,

Thanks. What subsets inside the current standard would you propose? What
interfaces between them would you envision?

Good idea about the optimization opportunities. Here's an initial
combined list, with the main benefits as I see them. Please
comment/extend.

- Dynamic process support: less overhead in the progress engine, easier
global rank handling.
- Heterogeneity: better memory footprint, easier data handling.
- Derived datatypes (especially those with holes): better memory
footprint.
- MPI_ANY_SOURCE: faster, more simple multifabric progress.
- File I/O: smaller requests, easier wait/test functions.
- One-sided ops: no passive target w/o MPI calls - no extra progress
thread.
- Communicator & group management: better memory footprint.
- Message tagging: better support for stable dataflow exchanges, smaller
packets.
- Non-blocking communication: easier ordering, simplified request
handling.

Best regards.

Alexander 

-----Original Message-----
From: mpi3-subsetting-bounces_at_[hidden]
[mailto:mpi3-subsetting-bounces_at_[hidden]] On Behalf Of
Torsten Hoefler
Sent: Friday, February 29, 2008 5:08 AM
To: mpi3-subsetting_at_[hidden]
Subject: Re: [Mpi3-subsetting] agenda for subsetting kickoff telecon
ww09

Hi,
>    Present: Leonid Meyerguz (Microsoft), Rich Graham (ORNL), Richard
Barrett
>    (ORNL), Torsten Hoefler (ISU), Alexander Supalov (Intel)
just for the record, it's "IU" not "ISU" :-)

>    - Scope of the effort
>      - Rich
>        - Minimum subset consistent with the rest of MPI, for
>    performance/memory footprint optimization
>        - Danger of splitting MPI, hence against optional features in
the
>    standard
I back that (danger of optional features for portability). I'd propose
to split the current standard into mostly self-contained subsets that
have clearly defined interfaces to the rest of the standard. Note: this
only defines logical interfaces, that does *not* define how those things
are to be implemented. This makes it easier to understand the standard
and have separate (portable) libraries for the subsets, it does not
influence optimization possibilities by implementing everything in a
monolithic block (i.e., central progress). 

>        - Both blocking & nonblocking belong to the core
>      - Torsten
>        - Some collectives may go into selectable subsets
I see three subsets: blocking colls, non-blocking colls and topological
colls (maybe also blocking / non-blocking).

>        - MPI_ANY_SOURCE considered harmful
I'd like to add datatypes and heterogeneity to this list (with regards
to performance). Alexander mentioned the dynamics. I think we should
have a lit of items ready that could influence optimization
possibilities significanty if they were to be announced by the user
before he can use them. That would give another strong argument for the
subsetting.

Best,
  Torsten


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