[Mpi3-bwcompat] MPI timer requests

[Fab Tillier]

Hi Rajeev,

In your example, what thread calls MPI_GREQUEST_COMPLETE?  What happens to the thread that is blocked in MPI_WAITANY when the signal comes in?

Thanks,
-Fab

Rajeev Thakur wrote on Tue, 8 Mar 2011 at 14:31:58

> Generalized requests could still be used in single threaded mode with
> signals (SIGALRM) I think.
> 
> Rajeev
> 
> 
> On Mar 8, 2011, at 1:09 PM, Dave Goodell wrote:
> 
>> Sure, that sounds like a reasonable justification.  I just wanted to make
> sure that you actually had that before you went forward to the Forum, since
> that's one of the things that I always ask when someone brings a new
> proposal to the whole group and it wasn't present on your original slides.
>> 
>> -Dave
>> 
>> On Mar 8, 2011, at 1:06 PM CST, Jeff Squyres wrote:
>> 
>>> I had to go back and read about generalized requests to remind myself
>>> how they worked...
>>> 
>>> But now I agree with Fab.  They won't work as timers except in
>>> THREAD_MULTIPLE + multiple threads scenarios.
>>> 
>>> So I think that the timers-as-requests idea still stands...
>>> 
>>> 
>>> On Mar 7, 2011, at 3:49 PM, Fab Tillier wrote:
>>> 
>>>> Jeff Squyres wrote on Mon, 7 Mar 2011 at 12:31:41
>>>>> 
>>>>> Dave's point about generalized requests is a good one, though -- I
>>>>> need to go think about that and convince myself that what we're
>>>>> talking about isn't syntactic sugar and/or why it's better to be in
>>>>> the MPI implementation.
>>>> 
>>>> In a MPI_THREAD_SERIALIZED implementation, you can't use call
> MPI_GREQUEST_COMPLETE if you're already calling MPI_WAITANY.
> Depending on generalized requests would require MPI_THREAD_MULTIPLE
> support for this functionality.
>>>> 
>>>> Note that for some implementations, making
> MPI_GREQUEST_COMPLETE thread-safe could be trivial, but there's no
> MPI_THREAD_MOSTLY_SERIALIZED option so there's no standard way of
> noting that some things are thread safe while others are not - it's either all
> or nothing.
>>>> 
>>>> -Fab
>>>> 
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>>> 
>>> --
>>> Jeff Squyres
>>> jsquyres_at_[hidden]
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>>> 
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