[Mpi-22] determine if running in a heterogenous environment

[Jeff Squyres]

On Mar 3, 2008, at 12:54 PM, Dries Kimpe wrote:

>> Narrowing the scope to "whether translation functionality is  
>> required"
>> is good.  But note that whether the translation functionality is used
>> may be specific to a given (communicator,peer,datatype) tuple.
>
> You're right that this depends on the communicator and on the peer;

...and the datatype.

> It would not be uncommon to have one 'different (memory representation
> wise)' node in the communicator. This could be a login node, a
> visualisation node, ...
>
> So, from a performance point of view (and also for the mpi  
> implementation
> internally), it's actually better to record this information for
> (communicator, source, dest). However, my main reason for this  
> proposal
> was to enable an application that doesn't care about datatypes  
> (might be
> more common than you'd think, looking at some of the mpi-subset  
> ideas) to
> abort execution if it detects that data conversion is needed when
> communicating to its peers.

My point is that some datatypes may require translation while others  
may not.  It's not always just endian differences -- sometimes there's  
floating point representation differences, or size differences (e.g.,  
sizeof(int) != sizeof(int)).


-- 
Jeff Squyres
Cisco Systems