[petsc-users] local to global mapping for DMPlex

[Yann JOBIC]

On 12/19/2017 05:50 PM, Matthew Knepley wrote:
> On Tue, Dec 19, 2017 at 11:40 AM, Yann JOBIC <yann.jobic at univ-amu.fr 
> <mailto:yann.jobic at univ-amu.fr>> wrote:
>
>     Hello,
>
>     We want to extract the cell connectivity from a DMPlex. We have no
>     problem for a sequential run.
>
>
> Do you want it on disk? If so, you can just DMView() for HDF5. That 
> outputs the connectivity in a global numbering.
> I can show you the calls I use inside if you want.
I looked at the code, specifically DMPlexWriteTopology_Vertices_HDF5_Static
cellIS should have what i want.
However it seems that it is not the case. Do i look at the right spot in 
the code ?

I also looked at DMPlexGetCellNumbering, which does exactly what i want 
for the global numbering of Cells, even if the ordering is different for 
different number of processors.
When i use DMPlexGetVertexNumbering, i've got negative values, which is 
correctly handeled by DMPlexWriteTopology_Vertices_HDF5_Static, but i 
really don't understand this part.
I succeed in having the coordinates, but maybe not in the right order. I 
reused DMPlexWriteCoordinates_HDF5_Static, which create a Vec of vertex 
coordinates, but i couldn't understand the order of vertex coordinate 
linked (or not) with DMPlexWriteTopology_Vertices_HDF5_Static. The 
number of local coordinates is also strange, and does not correspond to 
the cell's topology.

Thanks for the help!

Regards,

Yann


> I usually put
>
>   DMViewFromOptions(dm, NULL, "-dm_view")
>
> Then
>
>   -dm_view hdf5:mesh.h5
>
>   Thanks,
>
>     Matt
>
>     However for parallel ones, we need to get the node numbering in
>     the global ordering, as when we distribute the mesh, we only have
>     local nodes, and thus local numbering.
>
>     It seems that we should use DMGetLocalToGlobalMapping (we are
>     using Fortran with Petsc 3.8p3). However, we get the running error :
>
>     [0]PETSC ERROR: No support for this operation for this object type
>     [0]PETSC ERROR: DM can not create LocalToGlobalMapping
>
>     Is it the right way to do it ?
>
>     Many thanks,
>
>     Regards,
>
>     Yann
>
>
>
>
> -- 
> 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
>
> https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/%7Emk51/>

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