[petsc-users] PETSc/SLEPc: Memory consumption, particularly during solver initialization/solve

[Matthew Knepley]

On Wed, Oct 10, 2018 at 3:38 AM Ale Foggia <amfoggia at gmail.com> wrote:

> Jed, Jose and Matthew,
> I've finally managed to make massif (it gives pretty detailed information,
> I like it) work in the correct way in the cluster and I'm able to track
> down the memory consumption, and what's more important (for me), I think
> now I'm able to make a more accurate prediction of the memory I need for a
> particular size of the problem. Thank you very much for all your answers
> and suggestions.
>

Great! Could you tell me in one line what was taking up memory? It always
good to hear about real applications.

  Thanks,

    Matt


> El vie., 5 oct. 2018 a las 9:38, Jose E. Roman (<jroman at dsic.upv.es>)
> escribió:
>
>>
>>
>> > El 4 oct 2018, a las 19:54, Ale Foggia <amfoggia at gmail.com> escribió:
>> >
>> > Jose:
>> > - By each step I mean each of the step of the the program in order to
>> diagonalize the matrix. For me, those are: creation of basis, preallocation
>> of matrix, setting values of matrix, initializing solver,
>> solving/diagonalizing and cleaning. I'm only diagonalizing once.
>> >
>> > - Regarding the information provided by -log_view, it's confusing for
>> me: for example, it reports the creation of Vecs scattered across the
>> various stages that I've set up (with PetscLogStageRegister and
>> PetscLogStagePush/Pop), but almost all the deletions are presented in the
>> "Main Stage". What does that "Main Stage" consider? Why are more deletions
>> in there that creations? It's nor completely for me clear how things are
>> presented there.
>>
>> I guess deletions should match creations. Seems to be related to using
>> stages. Maybe someone from PETSc can give an explanation, but looking at a
>> PETSc example that uses stages (e.g. dm/impls/plex/examples/tests/ex1.c) it
>> seems that some destructions are counted in the main stage while the
>> creation is counted in another stage - I guess it depends on the points
>> where the stages are defined. The sum of creations matches the sum of
>> destroys.
>>
>> >
>> > - Thanks for the suggestion about the solver. Does "faster convergence"
>> for Krylov-Schur mean less memory and less computation, or just less
>> computation?
>> >
>>
>> It should be about the same memory with less iterations.
>>
>> Jose
>>
>>

-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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