itaps-parallel Two options from today's iMeshP phone conference

[Carl Ollivier-Gooch]

On 10-07-19 08:38 AM, Saurabh Tendulkar wrote:
>
>
> On 07/16/10 20:00, Carl Ollivier-Gooch wrote:
>> On 10-07-16 04:21 PM, Devine, Karen D wrote:
>>>
>>> A. Change the iMesh_createEnt function to include an entity set handle
>>> argument PH. For serial applications, PH would be the root set; that is,
>>> entities are added only to the root set. For parallel applications, PH
>>> would be a part handle; the created entity would be added to the part
>>> identified by the part handle. Since iMesh_createEnt is an iMesh
>>> function
>>> (not an iMeshP function), we would use entity set handle as the argument
>>> type, so that serial users would not have to include iMeshP.h nor
>>> link with
>>> iMeshP. This option was generally accepted by Carl, Simmetrix, Sandia
>>> and
>>> RPI. Tim is in favor of adding the argument, but does not like the
>>> restriction of the handle to be either the root set or a part handle. My
>>> fear in allowing arbitrary entity set handles to be used is as
>>> follows: if
>>> a service uses the entity set handle to, say, add entities to a boundary
>>> condition set, that service could not be used in parallel, as its
>>> iMesh_createEnt calls would not add the entities to a part.
>>>
>>> B. Add a new iMeshP function iMeshP_createEnt that takes as input a part
>>> handle. Parallel services would need to use iMeshP_createEnt to add
>>> entities, include iMeshP.h, and link with an iMeshP library;
>>> iMesh_createEnt
>>> would return an error. Serial services would continue to use
>>> iMesh_createEnt. This option is more explicit than option A, but
>>> requires
>>> more work on the user's part if the user wants code to work both with
>>> and
>>> without iMeshP.
>
> I think for A, we proposed that the argument be NULL in case of serial.
> If we want no restriction in iMesh, then maybe we can instead pass an
> array of entity sets to iMesh_createEnt, and then in iMeshP stipulate
> that one of them has to be a part.

In practice, that NULL would have to be the root set handle, since not 
all implementations use pointers as set handles.

>>> One point we didn't discuss but, perhaps, should have was when and how
>>> entity ownership should be assigned. The proposed changes add
>>> entities to
>>> parts, but do not address determining the ownership or copy-status of an
>>> entity. I am not sure where these issues should most appropriately be
>>> resolved; can they be postponed until iMeshP_syncPartitionAll?
>>
>> I had assumed that we were talking about setting ownership, since
>> that's the
>> real sticking point: entities that don't have an owner can't be
>> modified (as I
>> interpret the current spec).
>>
>> Carl
>
> Actually, no, we create different entities (ie. pointers) on different
> parts on the part boundary but only one part has the right to modify.
> The part is not modifying the entity in the _create function.

So we really do have two separate questions here:

1. What part should an entity be stored in, and
2. What part owns the entity.

In most cases, these are the same, but entities on part bdrys are 
different.  One way to deal with this would be to specify a part at 
creation time, with that part being set as owner, then call the 
(currently non-existent) setOwner function for entities on part bdrys. 
This latter call would have the advantage of explicitly identifying 
non-owned copies to the implementation, and could be useful when 
partitioning or reading a parallel mesh, as well as when modifying one.

Carl

-- 
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Dr. Carl Ollivier-Gooch, P.Eng.                   Voice: +1-604-822-1854
Professor                                           Fax: +1-604-822-2403
Department of Mechanical Engineering             email: cfog at mech.ubc.ca
University of British Columbia              http://www.mech.ubc.ca/~cfog
Vancouver, BC  V6T 1Z4                  http://tetra.mech.ubc.ca/ANSLab/
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