[petsc-users] Bad memory scaling with PETSc 3.10

[Myriam Peyrounette]

Here is the time weak scaling from the same study. The 3.10.2 version
seems to be much more stable with regard to the execution time. But not
necessarily faster for "large scale" simulations (problem size = 1e8).

I didn't use -mat_freeintermediatedatastructures. I tested it this
morning and the solver diverges when using this option (KSPReason -3).

Myriam


Le 04/09/19 à 17:23, Zhang, Hong a écrit :
> Myriam,
> Do you have 'execution time scalability' plot? Did you use
> '-mat_freeintermediatedatastructures' for PETSc 3.10.2?
> We made several computing optimizations on MatPtAP(), which might
> trade memory for speed. It would be helpful to see a complete comparison.
> Hong
>
> On Tue, Apr 9, 2019 at 7:43 AM Myriam Peyrounette via petsc-users
> <petsc-users at mcs.anl.gov <mailto:petsc-users at mcs.anl.gov>> wrote:
>
>     Hi,
>
>     in my first mail, I provided a memory scaling concerning the PETSc
>     example #42. You'll find attached the main files used (one for PETSc
>     3.6.4, one for PETSc 3.10.2), and the corresponding memory scaling.
>
>     In the main files, I modified the solver/preconditioner, so that it
>     corresponds to my problem. You'll find the modifications by searching
>     the keyword "TopBridge". In particular, I use GAMG.
>
>     Note that the example is about solving Stokes equation, so using GAMG
>     may not be adapted. However, the memory gap appears and that's the
>     point. No matter if the results are correct.
>
>     Are these scripts useful for you? Let me know.
>
>     Thanks,
>
>     Myriam
>
>
>     Le 04/04/19 à 00:09, Jed Brown a écrit :
>     > Myriam Peyrounette via petsc-users <petsc-users at mcs.anl.gov
>     <mailto:petsc-users at mcs.anl.gov>> writes:
>     >
>     >> Hi all,
>     >>
>     >> for your information, you'll find attached the comparison of
>     the weak
>     >> memory scalings when using :
>     >>
>     >> - PETSc 3.6.4 (reference)
>     >> - PETSc 3.10.4 without specific options
>     >> - PETSc 3.10.4 with the three scalability options you mentionned
>     >>
>     >> Using the scalability options does improve the memory scaling.
>     However,
>     >> the 3.6 version still has a better one...
>     > Yes, this still looks significant.  Is this an effect we can still
>     > reproduce with a PETSc example and/or using a memory profiler
>     (such as
>     > massif or gperftools)?  I think it's important for us to narrow down
>     > what causes this difference (looks like almost 2x on your 1e8
>     problem
>     > size) so we can fix.
>
>     -- 
>     Myriam Peyrounette
>     CNRS/IDRIS - HLST
>     --
>

-- 
Myriam Peyrounette
CNRS/IDRIS - HLST
--

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