[Mpi3-bwcompat] MPI_Count mixing with int...

[Rajeev Thakur]

You can define a filetype that is many Gbytes and read only a small part
of it. The filetype is specified in MPI_File_set_view and is not passed
in the read/write calls. The datatype passed in the read/write calls
refers to the buffer passed to that call.

Rajeev
 

> -----Original Message-----
> From: mpi3-bwcompat-bounces_at_[hidden] 
> [mailto:mpi3-bwcompat-bounces_at_[hidden]] On Behalf Of Fab Tillier
> Sent: Thursday, July 08, 2010 3:32 PM
> To: MPI-3 backwards compatability WG
> Subject: Re: [Mpi3-bwcompat] MPI_Count mixing with int...
> 
> Rajeev Thakur wrote on Thu, 8 Jul 2010 at 12:52:58
> 
> >> As an aside, can count ever be larger than size_t?
> > 
> > Probably not in the communication or I/O functions since 
> count refers 
> > to the number of items in the memory buffer, but it could 
> be for the 
> > datatype constructor functions since datatypes can 
> represent file layout.
> 
> How would you use a datatype that is larger than your address 
> space?  You can't read or write it, you can't send or receive 
> it, you can't pack/unpack it...
> 
> Am I missing something and a datatype like this would be useful?
> 
> -Fab
> 
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