itaps-parallel A question about iMeshP interface functions

[Carl Ollivier-Gooch]

Onkar Sahni wrote:
>> I had assumed that if one had a handle for an entity at all, that the
>> local
>> processor knew enough about that entity to answer such questions (e.g.
>> that
>> it is an interface or ghost entity.)  But I missed several discussions.
>> Are
>> we back to considering entity handles to be globally unique across all
>> processors?
> 
>   If entity-handle is local (on local part/proc.) then one can ask such
> questions (ghost entity etc.), but if entity is not local, i.e,
> remote-handle or remote-copt then it is not valid to ask such questions.
> How do we return reasonable error message/code in this case of
> remote-handle. There are no globally unique entity handles.

I'm a bit confused about what the problem is here.

First, I agree that we're certain to be looking at a local entity handle 
here (though it could be a ghost or copy).  There's simply no way to 
pass a remote entity handle --- that would require both a handle and a 
part ID.

Second, because a partition is a covering of the entire contents of a 
parallel mesh, checking whether an entity is in a partition reduces to 
checking whether the entity handle is valid in the local root set, a 
test that iMesh requires routinely.

>> It seems to me that the iMeshP_getEntOwnerPart and
>> iMeshP_getEntOwnerPartArr
>> are inherently expensive, and those are the only two for which I see a
>> requirement to return an error if the passed entity is not contained in
>> the
>> partition.  I'm looking at the draft spec Karen sent on July 24th.  Is
>> there
>> a more recent one?
> 
>   I do not see why these will be expensive, at least they are not in FMDB
> implementation.

If those are cheap, then surely checking for partition membership is too 
(if it belongs to a part, the entity surely belongs to the partition...).

Maybe I'm being incredibly naive here, but I don't see this as being 
terribly difficult or time consuming.  Am I missing something here?

Carl

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Dr. Carl Ollivier-Gooch, P.Eng.                   Voice: +1-604-822-1854
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