Hi, 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. Alexander -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Jeff Squyres 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

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