[Mpi-22] New proposal: Support for large message counts

[Richard Treumann]

MPI_Aint has the right number of bits to hold an address.  For operations
that are address space oriented, count can be the same size as an MPI_Aint

MPI_Offset has the right number of bits to deal with the range in a file.
For operations that are file oriented, arguments like count should be an
MPI_Offset

A problem is that MPI_Datatype constructors are intended to apply to both
and it is common for a 32 bit address space to operate on files with 64 bit
offsets.

What type should "count" on  the new "long" MPI_Datatype constructors be in
this case?  The proposal says MPI_Aint but that is awkward for datatypes as
fileviews.

Dick Treumann  -  MPI Team
IBM Systems & Technology Group
Dept X2ZA / MS P963 -- 2455 South Road -- Poughkeepsie, NY 12601
Tele (845) 433-7846         Fax (845) 433-8363

mpi-22-bounces_at_[hidden] wrote on 09/03/2008 12:38:35 PM:

> [image removed]
>
> Re: [Mpi-22] New proposal: Support for large message counts
>
> Supalov, Alexander
>
> to:
>
> MPI 2.2,
>
> 09/03/2008 12:48 PM
>
> Sent by:
>
> mpi-22-bounces_at_[hidden]
>
> Please respond to "MPI 2.2"
>
> Thanks. We may even do without changing the MPI routine names I think.
> Let's consider this:
>
> 1) #define MPI_Count int will yield the current MPI interface.
> 2) typedef int MPI_Count will yield the new 32-bit interface, still
> backward binary compatible with 1).
> 3) typedef long MPI_Count will yield new 64-bit interface.
> 4) typedef long long MPI_Count will safely bring us into XXII century
> (or earlier).
>
> Old applications may be rebuilt using 1) without any changes,
> dynamically linked against MPI library built using 2), and will have to
> be rebuilt to use MPI library built using 3) or 4).
>
> New applications will use library with the MPI_Count definitions, and,
> properly rebuilt, will work in either 32-, 64-, or 128-bit mode, using
> MPI libraries built using MPI bindings 2), 3), or 4), respectively.
>
> By the way, should MPI_Count really be signed?
>
> -----Original Message-----
> From: mpi-22-bounces_at_[hidden]
> [mailto:mpi-22-bounces_at_[hidden]] On Behalf Of Narasimhan,
> Kannan
> Sent: Wednesday, September 03, 2008 5:55 PM
> To: MPI 2.2
> Subject: Re: [Mpi-22] New proposal: Support for large message counts
>
> We can certainly consider this option, since it abstracts along the same
> lines as MPI_Offset.
>
> Thanx!
> Kannan
>
> -----Original Message-----
> From: mpi-22-bounces_at_[hidden]
> [mailto:mpi-22-bounces_at_[hidden]] On Behalf Of Supalov,
> Alexander
> Sent: Wednesday, September 03, 2008 10:19 AM
> To: MPI 2.2
> Subject: Re: [Mpi-22] New proposal: Support for large message counts
>
> Dear Kannan,
>
> Thanks. Why don't we define MPI_Count datatype instead, and make that
> grow if necessary?
>
> Best regards.
>
> Alexander
>
> -----Original Message-----
> From: mpi-22-bounces_at_[hidden]
> [mailto:mpi-22-bounces_at_[hidden]] On Behalf Of Narasimhan,
> Kannan
> Sent: Friday, August 29, 2008 6:15 PM
> To: mpi-22_at_[hidden]
> Subject: [Mpi-22] New proposal: Support for large message counts
>
> I have submitted a new 2.2 proposal to addresses the need for large
> message counts (i.e. counts greater than the size of 32-bit integer) for
> MPI calls that communicate messages.
>
> Please refer to
> https://svn.mpi-forum.org/trac/mpi-forum-web/wiki/mpi22/LargeMsgCounts
> for details.
>
> Comments and suggestions are welcome.
>
> Thanx!
> Kannan
>
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