itaps-parallel More questions on iMeshP

[Jason Kraftcheck]

Saurabh Tendulkar wrote:
> 
> 
> Jason Kraftcheck wrote:
>> Saurabh Tendulkar wrote:
>>> We have the following further questions about iMeshP.
>>>
>>> 1. iMeshP_destroyPartitionAll states that the partition is not
>>> invalidated upon return. If this means that the partition is not freed,
>>> when and how will it be freed? If not, what does the statement mean?
>>>
>>
>> There was some debate at one time as to whether or not this type of
>> function
>> should be passed a partition handle by copy (as it is now) or instead be
>> passed a reference to a partition handle so that the implementation can
>> nullify the variable storing the handle.  I assume that this comment
>> refers
>> to the passed variable containing the handle value, rather than the
>> partition itself.
> 
> If I understand this correctly then, the statement should be disregarded
> because it doesn't make sense in the context of the handle being passed
> by value?
> 

That is my interpretation.

> 
>>
>>> 2. Several migration functions take in the destination part ids of
>>> entities as they should. However, there is no function to get remote
>>> part ids from a partition. How is the user supposed to know which part
>>> id to migrate to, or are we missing something?
>>>
>>
>> iMeshP_getPartNBors(Arr)
>> iMeshP_getEntOwnerPart(Arr)
>> iMeshP_getCopyParts
>>
> 
> These are just returning the part wrt an entity (ownership/copy) or
> neighboring a part. Isn't there anything that returns them in a global
> sense (eg. return all part ids on process with given rank)?
> 

There doesn't appear to be.  It seems that there should be a
iMeshP_getGlobalParts, as we have: iMeshP_getNumGlobalParts,
iMeshP_getNumLocalParts, and iMeshP_getLocalParts.  On the other hand,
that's typically all-to-all communication and perhaps the intent was to
discourage it.  It also may not scale well to very large machines for other
reasons (big array to hold all part ids.)  Perhaps you could just assume
that parts have consecutive IDs (which I think is the case for all
implementations), and therefore assume that the global part list is 1 to n,
where n is the result of iMeshP_getNumGlobalParts.

- jason