[mpich-discuss] MPICH2 & Large dat

[Nicolas Rosner]

Yes, but what he is suggesting is that you could "lie" to MPI about
the data type.  For example, if you wanted to send 1000 MPI_CHARs, you
could instead send them as if they were 250 MPI_INTs (assuming an int
takes up as much space as four chars on your system).  Since 250 is a
smaller count than 1000, this could be of use to you (because your
problem is that the count is becoming too big).

Of course, you need to be extra careful if you try this, for it could
affect portability (after all, the whole point of having symbolic
datatypes like MPI_INT for in-flight data is to avoid having to
remember, or even assume, that an int takes up four bytes).

HTH,
Nicolás


On 10/2/08, Hisham Adel <hosham2004 at yahoo.com> wrote:
> The problem is in the count number not in the data type.
>
> Thanks  a lot
>
>
>
> --- On Thu, 10/2/08, The Source <thesourcehim at gmail.com> wrote:
> From: The Source <thesourcehim at gmail.com>
> Subject: Re: [mpich-discuss] MPICH2 & Large data
> To: mpich-discuss at mcs.anl.gov
> Date: Thursday, October 2, 2008, 3:08 PM
>
>  Send, using different MPI data types. For example MPI_INT instead of
> MPI_CHAR, so element number will be 4 time smaller. The other way is to
> split data to several messages.