[mpich-discuss] MPI_Alltoallv with long* for displacements instead of int*

[Raghu Reddy]

Thank you Dave!

I'm sure it is obvious why I was asking for this, but just to be documented 
in the thread I should have explicitly mentioned that the displacements I 
was dealing with are larger than the value that can be held in an int.

Machines with more memory than 2 GB/core are fairly common, and if one were 
to use 1 MPI rank per node, then it is very much possible to run into these 
limits.

Should this be recommend to be considered for the next standard?

Thanks again for the prompt response!

--rr
Please Note: Email transcribed by speech recognition; May have unintended
words in some cases, especially when I fail to do a good job of
proofreading!

--On Thursday, March 24, 2011 3:36 PM -0500 Dave Goodell 
<goodell at mcs.anl.gov> wrote:

> On Mar 24, 2011, at 3:25 PM CDT, Raghu Reddy wrote:
>
>> Currently the type signature for this routine from the Synopsis is:
>>
>> # include "mpi.h"
>> int MPI_Alltoallv (
>>       void *sendbuf,
>>       int *sendcnts,
>>       int *sdispls,
>>       MPI_Datatype sendtype,
>>       void *recvbuf,
>>       int *recvcnts,
>>       int *rdispls,
>>       MPI_Datatype recvtype,
>>       MPI_Comm comm )
>>
>> Is there a version of this routine with long* instead of int* for
>> displacements?
>
> No, such a routine is not specified by the MPI-2.2 standard, and MPICH2
> contains no non-standard extension that would accomplish the same thing.
>
> The MPI Forum is currently considering possible fixes for general problem
> for the upcoming MPI-3 standard.  However, I am not sure that this
> particular routine will be addressed in any way.
>
> -Dave
>
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