[petsc-users] pcfieldsplitting not working for VI

[Justin Chang]

FWIW I ended up doing this:

rs_solver.setDM(W._dm())

and was left with this error:

Traceback (most recent call last):
  File "sphere.py", line 180, in <module>
    virs()
  File "sphere.py", line 163, in virs
    rs_solver.solve(None,sol_vec)
  File "PETSc/SNES.pyx", line 537, in petsc4py.PETSc.SNES.solve
(src/petsc4py.PETSc.c:170012)
petsc4py.PETSc.Error: error code 75
[0] SNESSolve() line 4060 in
/private/var/folders/92/1kh0g4kn2z50fnwsmf8s269w0000gn/T/pip-gYEj0p-build/src/snes/interface/snes.c
[0] SNESSolve_VINEWTONRSLS() line 424 in
/private/var/folders/92/1kh0g4kn2z50fnwsmf8s269w0000gn/T/pip-gYEj0p-build/src/snes/impls/vi/rs/virs.c
[0] MatGetSubMatrix() line 7929 in
/private/var/folders/92/1kh0g4kn2z50fnwsmf8s269w0000gn/T/pip-gYEj0p-build/src/mat/interface/matrix.c
[0] MatGetSubMatrix_Nest() line 451 in
/private/var/folders/92/1kh0g4kn2z50fnwsmf8s269w0000gn/T/pip-gYEj0p-build/src/mat/impls/nest/matnest.c
[0] MatNestFindSubMat() line 424 in
/private/var/folders/92/1kh0g4kn2z50fnwsmf8s269w0000gn/T/pip-gYEj0p-build/src/mat/impls/nest/matnest.c
[0] MatNestFindIS() line 363 in
/private/var/folders/92/1kh0g4kn2z50fnwsmf8s269w0000gn/T/pip-gYEj0p-build/src/mat/impls/nest/matnest.c
[0] Arguments are incompatible
[0] Could not find index set

I must be doing something wrong here.

Justin

On Tue, Nov 29, 2016 at 1:24 AM, Justin Chang <jychang48 at gmail.com> wrote:

> Lawrence,
>
> I added the following line:
>
> rs_solver.setDM(a._dm)
>
> And it gives this error:
>
> Traceback (most recent call last):
>   File "sphere.py", line 128, in <module>
>     rs_solver.setDM(a._dm)
> AttributeError: 'Form' object has no attribute '_dm'
>
> Thanks,
> Justin
>
> On Tue, Nov 29, 2016 at 1:12 AM, Lawrence Mitchell <
> lawrence.mitchell at imperial.ac.uk> wrote:
>
>>
>>
>> > On 29 Nov 2016, at 02:02, Justin Chang <jychang48 at gmail.com> wrote:
>> >
>> > Why is this happening? It seems to me VINEWTONRSLS is not understanding
>> that I have a two-field formulation.
>>
>> For the built in solvers, we set up a dmshell on the snes that knows how
>> to do field splitting.  Because you set your snes up by hand, it isn't
>> available. You'll need to call snes.setDM. The mixed finctionspace provides
>> the correct dm via a ._dm property I think.
>>
>> Lawrence
>>
>
>
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