[MPICH] IMB Exchange

[Calin Iaru]

Thanks Rajeev. It's certainly useful. So MPI_Waitall is not actually needed.

Rajeev Thakur wrote:
> 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.
>>
>>
>>     
>
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