[petsc-users] [EXT]Re: Is using PETSc appropriate for this problem

[Alexander B Prescott]

Thank you all for your input. Matt is right, I cannot batch as this
formulation must be done sequentially.

>>  Sounds a bit like a non-smoother (Gauss-Seidel type), speculating based
on these few words.

Barry, it is similar to a Gauss-Seidel solver in that solution updates from
previous solves are used in the most recent Newton solve, though I'm not
exactly sure what you mean by "non-smoother".

Best,
Alexander



On Thu, Sep 17, 2020 at 6:06 AM Matthew Knepley <knepley at gmail.com> wrote:

> *External Email*
> On Thu, Sep 17, 2020 at 12:23 AM Jed Brown <jed at jedbrown.org> wrote:
>
>> Alexander B Prescott <alexprescott at email.arizona.edu> writes:
>>
>> >>      Are the problems of varying nonlinearity, that is will some
>> converge
>> >> with say a couple of Newton iterations while others require more, say
>> 8 or
>> >> more Newton steps?
>> >>
>> > The nonlinearity should be pretty similar, the problem setup is the
>> same at
>> > every node but the global domain needs to be traversed in a specific
>> order.
>>
>>
>> It sounds like you may have a Newton solver now for each individual
>> problem?  If so, could you make a histogram of number of iterations
>> necessary to solve?  Does it have a long tail or does every problem take 3
>> and 4 iterations (for example).
>>
>> If there is no long tail, then you can batch.  If there is a long tail,
>> you really want a solver that does one problem at a time, or a more dynamic
>> system that checks which have completed and shrinks the active problem
>> down.  (That complexity has a development and execution time cost.)
>>
>
> He cannot batch if the solves are sequential, as he says above.
>
>    Matt
>
> --
> 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/>
>


-- 
Alexander Prescott
alexprescott at email.arizona.edu
PhD Candidate, The University of Arizona
Department of Geosciences
1040 E. 4th Street
Tucson, AZ, 85721
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20200917/97144c0c/attachment.html>