[petsc-users] A question about ghost cells

[Matthew Knepley]

On Fri, Oct 28, 2016 at 8:05 AM, leejearl <leejearl at 126.com> wrote:

> Hi, Matt:
>     Thank you for your help. It is the answer which I expect.
>     But， I have an another equestion. Can I obtain the coordinates of the
> ghost cells:
>

I am not sure I understand. By default, Plex stores coordinates only for
vertices. Also, ghost cells
do not have a full complement of vertices because they are only used to
define a state on the other
side of a face. Does that make sense?

  Matt


>     Thanks,
>
> leejearl
>
> On 2016年10月28日 19:56, Matthew Knepley wrote:
>
> On Fri, Oct 28, 2016 at 6:32 AM, leejearl <leejearl at 126.com> wrote:
>
>> Hi, everyone:
>>
>>     I have a distributed DMPlex representing a 2D finite volume mesh. I
>> distributed it using the function "DMPlexDistribute()".
>>
>> Then, I constructed the ghost cells using "DMPlexConstructGhostCells()".
>>
>>    The question is that I want to determine which cell is ghosted. I
>> obtained all the cells using "DMPlexGetHeightStratum()", and
>>
>> how can I kown which cell is ghosted?
>>
>
> 1) The ghost cells are marked as "hybrid", so you can call
>
>   ierr  = DMPlexGetHybridBounds(dm, &cEndInterior, NULL, NULL,
> NULL);CHKERRQ(ierr);
>   ierr  = DMPlexGetHeightStratum(dm, 0, NULL, &cEnd);CHKERRQ(ierr);
>
> and then the ghost cells are [cEndInterior, cEnd).
>
> 2) There is also a label "ghost" which marks the ghost faces, and ghost
> cells which are non-local
>
>   Thanks,
>
>     Matt
>
>
>>    Thanks, all the helps are appreciated.
>>
>>
>> leejearl
>>
>>
>>
>>
>
>
> --
> 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
>
>
>


-- 
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
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