[MPICH] bsend behavior differences

[William Gropp]

A portable program can only be sure that the information has been  
send when MPI_Buffer_detach is called.  MPICH2 will try to send the  
data earlier, but some of this will depend on the underlying  
communication method, the sizes of the messages, and when the  
receives are posted.  Your best bet is to use MPI_Buffer_detach when  
you need to know for sure that the messages have been sent.

Bill

On Jan 8, 2008, at 9:58 AM, Vlad Branzoi wrote:

> Hi,
>
> I have a question about the behavior of buffered send on different  
> machines.
> On one machine MPI seems to send stuff from the buffer on a  
> consistent basis
> while on another machine it only sends messages out when I 'flush' the
> buffer via a buffer_detach and buffer_attach.  What could be  
> causing this
> different behavior, and is there a way to make it consistent.
>
> Both machines are running MPICH2 1.0.6p1.  The first one is running  
> WinXP
> 32-bit version and the 2nd machine is running WinXP 64-bit version,  
> however
> both are running the 32-bit version of MPICH2.
>
> Thanks,
> Vlad
>

William Gropp
Paul and Cynthia Saylor Professor of Computer Science
University of Illinois Urbana-Champaign


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