[petsc-users] Nested field split

[Matthew Knepley]

On Wed, May 17, 2023 at 3:23 PM Matthew Knepley <knepley at gmail.com> wrote:

> On Wed, May 17, 2023 at 2:59 PM Barry Smith <bsmith at petsc.dev> wrote:
>
>>
>>   Absolutely, that is fundamental to the design.
>>
>>   In the simple case where all the degrees of freedom exist at the same
>> grid points, hence storage is like  u,v,t,p   in the vector the nesting is
>> trivial. You indicate the fields without using IS (don't even need to
>> change any code)
>>
>> -pc_fieldsplit_0_fields 0,1,2
>> -fieldsplit_pc_fieldsplit_0_fields  0,1
>>
>> Listing the two complimentary fields
>> pc_fieldsplit_1_fields 3
>> -fieldsplit_pc_fieldsplit_1_fields  2
>> should be optional (I can't remember if it is smart enough to allow not
>> listing them)
>>
>> If you have a staggered grid then indicating the fields is trickery
>> (since you don't have the simple u,v,t,p layout of the degrees of freedom)
>>
>
> Here we do something similar.
>

The URL was missing: https://arxiv.org/abs/1808.08328

  Thanks,

    Matt


>   Thanks,
>
>      Matt
>
>
>> > On May 17, 2023, at 12:47 PM, Alexander Lindsay <
>> alexlindsay239 at gmail.com> wrote:
>> >
>> > I've seen threads in the archives about nested field split but I'm not
>> sure they match what I'm asking about.
>> >
>> > I'm doing a Schur field split for a porous version of incompressible
>> Navier-Stokes. In addition to pressure and velocity fields, we have fluid
>> and solid temperature fields. I plan to put all primal variables in one
>> split and the pressure obviously in the Schur split. Now within the "primal
>> variable split" a user is wondering whether we can do a further split, e.g.
>> perhaps an additive split with the solid temperature split out from the
>> velocities and fluid temperature (the former is almost pure conduction
>> whereas the latter may be advection dominated). Is this possible?
>> >
>> > Alex
>>
>>
>
> --
> 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/>
>


-- 
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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