[MOAB-dev] exchange tags over interface entities

[Tim Tautges]

Hi Lorenzo,
   I need you to be a little more specific:
1) Do you want to push tags from owner proc to sharing, or from sharing to owner?
2) Do you want to do a global id just for interface entities (which might have been created during the resolve interface 
step of loading) or for any/all shared entities?

For 1), the existing exhcange_tags functions in ParallelComm push tag values from owner to sharers, for both interface 
and ghost entities.  I'm going to commit very soon (this week) a function called tag_reduce, that applies on MPI_Op to 
tag data on all sharers from all sharers, e.g. sums values on all sharers (including owner) and stores in another tag on 
all sharers.

For 2), first, 3D entities and vertices already have global ids when they get loaded, though those might not be 
communicated when something gets ghosted.  To do that, call exchange_tags with the GLOBAL_ID tag.  For other entities, 
the ParallelComm::assign_global_ids function should do what you want.

- tim


On 03/06/2012 12:45 PM, Lorenzo Alessio Botti wrote:
> Hi all,
> I have a question about exchanging tags in parallel.
> I guess I'd need to create a layer of ghost interface (dim-1) entities that replicates the behavior of ghost (dim) cells.
> In particular what I need is a global id for interface entities which is independent of the owning processor.
> And of coarse each interface entity should be able to know the global id of his ghost interface entity.
> Is it possible?
>
> Another possibility would be to communicate tag values over non_owned interface entities towards owned interface entities.
> A sort of exchange_tags that works on the opposite direction. Is it possible in some way?
>
> Thanks a lot for help.
> Lorenzo
>

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              Tim Tautges            Argonne National Laboratory
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