[petsc-users] Using DM_BOUNDARY_GHOSTED in DMSTAG

[Colton Bryant]

Hello,

I'm trying to understand the use of DM_BOUNDARY_GHOSTED and am a little
confused. Is there any way for the linear solver to access and manipulate
the ghost point value during the solve? I currently have a code using
DM_BOUNDARY_PERIODIC and at the periodic boundary I simply apply the same
discretization as I do everywhere else and as I understand it the value at
e.g. i=-1 is set automatically by the periodic boundary condition. I would
like to use DM_BOUNDARY_GHOSTED to set my own condition by which the point
at i=-1 is set (a Neumann type condition). I have seen some matrix free
examples but is there an easy way to "add" such a condition to the linear
system in this case?

Thanks for any help you can provide.

Best,
Colton Bryant
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