itaps-parallel definition for 'neighbors of a part'

[Carl Ollivier-Gooch]

Tim Tautges wrote:
> "Objects for which ownership is clearly defined" will definitely be 
> different than "objects in the partition", both in the case of 
> lower-dimensional entities (which aren't in the 2nd group) and multiple 
> partitions (where you have to qualify which partition you're talking 
> about).
> 
> Also, now that we're discussing getNumOfTypePar, we should also allow in 
> this function for passing something equivalent to "no partition" and "no 
> set", so that an application can find information about the global mesh, 
> independent of partition.  This will be important for example when 
> multiple partitions exist with partitioned objects of different 
> dimension (think 3d region partition and surface face partition, where 
> objects in the face partition can bound objects in the region partition).

This both addresses my concern about (what I think of) as the obvious 
global query and has a parallel (pun intended) to the root set formalism 
that we already use in serial.

But will this integrate seamlessly with, for instance, iterators?

Suppose I have partitioned my mesh on the basis of regions, but now I 
want to iterate over faces within each part (for swapping, or for a 
solver, or for some other reason).  If the part is a covering of the 
partition, and the partition contains only the regions, I've got nothing 
to iterate over (or query or count).  Either that, or the union of parts 
has different membership than the partition and the sum of getNumOfType 
by parts isn't getNumOfTypePar for the partition...

Fundamentally, it looks like we may need two families of functions, one 
that acts only on the entities that were used for division into parts, 
and one that acts on all the entities in the mesh.  I suspect that, 
except for partitioning, the latter is likely to be used/usable 
overwhelmingly more often.  So that's the one that I think we should 
mean when we count entities, do entity queries, and create iterators in 
the "natural" iMesh-like ways.  Queries related to what was used for 
division into parts have a place, too, and I'm certainly not saying we 
shouldn't preserve that information, but IMO that place is secondary.

Of course, I may be overlooking some large class of use cases where the 
notion of all entities of a particular dimension or topology with local 
right-to-modify just isn't adequate.  Obviously, I'm having trouble 
imagining what those would be. :-)

Carl

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