[MPICH] IMB Exchange

[Rajeev Thakur]

It is ok to call the waitall after the receives. While blocked in the
receive, the MPI implementation will cause progress on other previously
issued communication. It cannot just make progress on the currently issued
receive.

Rajeev 

> -----Original Message-----
> From: owner-mpich-discuss at mcs.anl.gov 
> [mailto:owner-mpich-discuss at mcs.anl.gov] On Behalf Of Calin Iaru
> Sent: Thursday, November 15, 2007 6:01 AM
> To: mpich-discuss at mcs.anl.gov
> Subject: [MPICH] IMB Exchange
> 
> I am looking at IMB Excahnge implementation which is:
>   - asynchronous send to left and right rank
>   - blocking receive from left and right
>   - Waitall
> What I don't understand is why is blocking receive followed 
> by Waitall. 
> If all nodes are doing async send which are not guaranteed to 
> complete, then the receive operation is not satisfied. Let me 
> know your opinion. I would expect that waitall is after async send.
> 
>