[petsc-users] DMPlex shared node indexing

[Barry Smith]

https://gitlab.com/petsc/petsc/-/merge_requests/4542/diffs?commit_id=252cf7895bb78ed4e3a2388b4d15d1e7905925a9 <https://gitlab.com/petsc/petsc/-/merge_requests/4542/diffs?commit_id=252cf7895bb78ed4e3a2388b4d15d1e7905925a9>

If you use the option -dm_plex_use_vec_ghost_permutation then ghost values will be put at the end of the local vector. Note this is work in progress so will have rough edges.


> On Nov 27, 2021, at 10:54 AM, 袁煕 <yuanxi at advancesoft.jp> wrote:
> 
> Great! It is of much help to me. But I am not sure how to use it.  Does it mean   ghost vertices are put at the end of the local vector  automatically after calling DMPlexDistribute? Or additional function calling or setting is needed?
> 
> Yuan
> 
> 2021年11月27日(土) 0:34 Barry Smith <bsmith at petsc.dev <mailto:bsmith at petsc.dev>>:
> 
>    Actually, with DMPLEX the ghost vertices are not at the end of the local vector, they can be anywhere within the list. 
> 
>    But I have a work-in-progress branch https://gitlab.com/petsc/petsc/-/merge_requests/4542 <https://gitlab.com/petsc/petsc/-/merge_requests/4542> that labels the ghost locations and moves them to the end. You are welcome to try it.
> 
>   Barry
> 
> 
>> On Nov 26, 2021, at 8:16 AM, Mark Adams <mfadams at lbl.gov <mailto:mfadams at lbl.gov>> wrote:
>> 
>> First, ghost vertices only show up in "local" (vs "global") vectors and the ghost values are ordered after the locally owned ones.
>> Others might have more to add.
>> Mark
>> 
>> 
>> On Fri, Nov 26, 2021 at 12:49 AM 袁煕 <yuanxi at advancesoft.jp <mailto:yuanxi at advancesoft.jp>> wrote:
>> Dear PETSc-team,
>> 
>> When the mesh is distributed, the vertices are renumbered and some vertices are shared by neighboring CPUs. My question is:
>> 
>> 1. How to check which vertice is a ghost one?
>> 2. Are those ghost vertices always at the end of vertices list? If not
>> 3. Are there simple ways to let those ghost vertices come after owned ones?
>> 
>> Many thanks
>> 
>> Yuan
> 

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