[mpich-discuss] sequencing non-blocking requests

[Martin Pokorny]

Dave Goodell wrote:
> On May 4, 2012, at 12:14 PM CDT, Martin Pokorny wrote:
> 
>> Hi, all; I'm trying to create a generalized request out of a
>> sequence of regular requests. I've implemented this using the
>> extended generalized request "class" with a wait function to check
>> and make progress on the sequence of requests. Within the wait
>> function of the generalized request, I'd like to call MPI_Testall
>> on some subset of the current (sub-)requests, but I'm uncertain
>> about whether that is safe. In my implementation this works much of
>> the time, but occasionally there are apparent deadlocks (however,
>> I'm not sure of the cause). I'm wondering whether or not it's OK to
>> recursively call MPI_Testall and other, similar functions from the
>> wait function of the generalized request without special measures.
>> Any insight would be appreciated.
> 
> This isn't really supported usage.  My guess is that the progress
> engine and generalized request code will tolerate it for a variety of
> scenarios, but it certainly wasn't designed with this case in mind
> and it probably has at least one insidious bug hiding somewhere.

Thanks for the information. I should be able to re-implement my code 
without resorting to this unsupported usage of generalized requests with 
little or no ill effect, so I can avoid these apparent and/or latent 
problems.

-- 
Martin