[petsc-dev] PETSc issue I cannot post combine WaitForCUDA(); inside PetscLogGpuTimeEnd();

[Karl Rupp]

Hi,

>    Since we cannot post issues (reported here 
> https://forum.gitlab.com/t/creating-new-issue-gives-cannot-create-issue-getting-whoops-something-went-wrong-on-our-end/41966?u=bsmith) 
> here is my issue so I don't forget it.
> 
>    I think
> 
>   err  = WaitForCUDA();CHKERRCUDA(err);
>   ierr = PetscLogGpuTimeEnd();CHKERRQ(ierr);
> 
> should be changed to include WaitForCUDA() actually WaitForDevice() 
> inside the PetscLogGpuTimeEnd().
> 
> Currently sometimes the WaitForCUDA() is missing in a few places 
> resulting in bad timing.
> 
> Also some _SeqCUDA() don't have the PetscLogGpuTimeEnd() and need to be 
> fixed.
> 
> The current model is a maintenance nightmare.
> 
> Does anyone see a problem with making this change?

I'm fine with this change, as the maintenance benefits outweigh the 
performance cost for typical use cases.

I propose to also add the WaitForDevice(); at PetscLogGpuTimeBegin(). 
This will ensure that no previous GPU kernel executions spill over into 
the timed section.

Best regards,
Karli