Subject: data representation

From: [email-masked] (Rolf Hempel)
Date: Wed, 22 Jun 1994 15:56:13 +0200

Hi folks,

during our work on an automatic PARMACS-->MPI translator the following
question came up: how can an MPI-process find out whether another
process runs on a processor with the same data representation or not?
In the first case I can just send a PARMACS buffer as type MPI_BYTE
without bothering about its contents, whereas in the second case I
have to do something special for every segment of the message. (A
message segment contains data of one type only.) For performance
reasons I don't want to go the second way in the 95% of cases where the
representations match.

I hoped for finding an inquiry function in the Environmental Management
section. The function MPI_GET PROCESSOR_NAME does not help, because
it gives different strings for different processors, not for different
types of processors.

Any brilliant idea? The only obvious way seems to be to send a test
message and look if the received message matches the original. However,
this method is not very precise, and complicated to use.

- Rolf

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From: Tony Skjellum <[email-masked]>
Date: Wed, 22 Jun 94 11:33:48 CDT

Rolf, MPI assumes that the information on process types will be managed
with groups or with communicators.  Specifically, a property of a communicator
could be its conversion protocol among its members.

So, your PARMACS translator should not need to address this issue. It must
be addressed by implementations of MPI that you use with your applications
thereafter.

-Tony

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