[petsc-dev] GAMG and custom MatMults in smoothers

[Vaclav Hapla]

OK, now I got you. So I think it's actually not that important when they are created but whether and in which order they are registered on different ranks (see attached edited MWE). Yes, that's a relevant concern I must admit, mainly for things working with subcomms.

Thanks

Vaclav

> 2. 7. 2018 v 17:57, Stefano Zampini <stefano.zampini at gmail.com>:
> 
> The intent was not to show you a deadlock; was to provide you evidence that the PetscLogEvent model is meant to have the same event created collectively (hopefully at class registration) on all processes. See also PetscLogViewDefault
> 
> 2018-07-02 18:45 GMT+03:00 Vaclav Hapla <vaclav.hapla at erdw.ethz.ch <mailto:vaclav.hapla at erdw.ethz.ch>>:
> Thanks for the MWE. But it behaves exactly as I would anticipate, see log. I think that naming the event differently for each rank is not good but fortunately PETSc just ignores this for rank > 0. Important is the event id which is the same. I correctly get that the time spent in this event is slightly more than 8 s and the ratio between the shortest and the longest time among all ranks is 8.0.
> 
> Where's the deadlock? Note that PetscLogEventBegin/End and PetscStageLogPush/Pop are not collective!
> 
> And thanks for another argument for better specificity of the log view. If the same event would be nested at several levels, the obtained total time wouldn't say anything useful.
> 
> Thanks
> 
> Vaclav
> 
> 
> 
>> 2. 7. 2018 v 17:20, Stefano Zampini <stefano.zampini at gmail.com <mailto:stefano.zampini at gmail.com>>:
>> 
>> 
>> 
>> 
>> I don't see why this should lead to deadlock? With current class-wise events you can already have many simultaneous instances of the same event at once.
>> 
>> 
>> Attached a MVE to better explain myself. If you run with p processes, you will see what I mean
>> 
>>  
>> 
>> -- 
>> Stefano
>> <log.c>
> 
> 
> 
> 
> 
> -- 
> Stefano

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