[MPI3 Fortran] Proposing changes to Fortran 2008

Supalov, Alexander alexander.supalov at intel.com
Thu Mar 20 14:49:45 CDT 2008


The datatypes used in several concurrent operations may describe
portions of data that overlap (hole/dataA, dataB/hole). In this case
sending the holes will violate the standard I'm afraid.

Best regards.


-----Original Message-----
From: mpi3-fortran-bounces at lists.mpi-forum.org
[mailto:mpi3-fortran-bounces at lists.mpi-forum.org] On Behalf Of Jeff
Sent: Thursday, March 20, 2008 8:27 PM
To: MPI-3 Fortran working group
Subject: Re: [MPI3 Fortran] Proposing changes to Fortran 2008

On homogeneous architectures -- where the same hardware and software  
is used on all sides (to include the compiler) -- yes, this will  
likely work just fine.  And probably most people do this, because it  
can be quite a bit easier.

If your data is dense in memory, that's probably "good enough". If  
your data is sparse, you could end up sending quite a bit of garbage  
along with your real data, decreasing the bandwidth available to your  
app, potentially adding more latency, etc.

In heterogeneous situations (where any of the above assumptions is not  
true), it clearly may not work properly.

On Mar 20, 2008, at 1:47 PM, Aleksandar Donev wrote:
> On Thursday 20 March 2008 10:35, Jeff Squyres wrote:
>> because the
>> user application will have had to created an MPI datatype *at run
>> time* that will have accurate offsets/types of each member.
> Out of curiosity: Have you seen codes that actually do that?
> What I would do, to make my life simple, is treated the whole scalar  
> of
> derived type as a blob of memory and ignored what fields are  
> actually inside,
> in what order, and with what padding. On homogeneous architectures  
> doesn't
> this work just fine?
> Aleks
> _______________________________________________
> mpi3-fortran mailing list
> mpi3-fortran at lists.mpi-forum.org
> http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi3-fortran

Jeff Squyres
Cisco Systems

mpi3-fortran mailing list
mpi3-fortran at lists.mpi-forum.org
Intel GmbH
Dornacher Strasse 1
85622 Feldkirchen/Muenchen Germany
Sitz der Gesellschaft: Feldkirchen bei Muenchen
Geschaeftsfuehrer: Douglas Lusk, Peter Gleissner, Hannes Schwaderer
Registergericht: Muenchen HRB 47456 Ust.-IdNr.
VAT Registration No.: DE129385895
Citibank Frankfurt (BLZ 502 109 00) 600119052

This e-mail and any attachments may contain confidential material for
the sole use of the intended recipient(s). Any review or distribution
by others is strictly prohibited. If you are not the intended
recipient, please contact the sender and delete all copies.

More information about the mpiwg-fortran mailing list