Are you referring to the text?
. `DM_BOUNDARY_MIRROR` - the ghost value is the same as the value 1 grid point
in; that is, the 0th grid point in the real mesh acts like a mirror to define
the ghost point value; not yet implemented for 3d
Looking at the code for DMSetUp_DA_3D() I see
PetscCheck(stencil_type != DMDA_STENCIL_BOX || (bx != DM_BOUNDARY_MIRROR &&
by != DM_BOUNDARY_MIRROR && bz != DM_BOUNDARY_MIRROR),
PetscObjectComm((PetscObject)da), PETSC_ERR_SUP, "Mirror boundary and box
stencil");
which seems (to me) to indicate the mirroring is not done for box stencils but
should work for star stencils.
Are you using a star stencil or a box stencil?
I believe the code is not complete for box stencil because the code to
determine the location of the "mirrored point" for extra "box points" is messy
in 3d and no one wrote it. You can compare DMSetUp_DA_2D() and DMSetUp_DA_3D()
to see what is missing and see if you can determine how to add it for 3d.
Barry
> On Jan 4, 2024, at 1:08 PM, Gourav Kumbhojkar <[email protected]>
> wrote:
>
> Hi,
>
> I am trying to implement a No-flux boundary condition for a 3D domain. I
> previously modeled a no flux boundary in 2D domain using DMDACreate2D and
> “PETSC_BOUNDARY_MIRROR” which worked well.
> However, the manual pages say that the Mirror Boundary is not supported for
> 3D.
> Could you please point me to the right resources to implement no flux
> boundary condition in 3D domains?
>
> Regards,
> Gourav K.
