itaps-parallel Questions about iMeshP

[Mark Beall]

OK. Then in practice, what you're really going to have is one  
partitioning of a mesh and another partitioning of a copy (or  
ghosting) of that mesh (or a portion of it). If there is very little  
correlation between the two partitionings then it doesn't seem worth  
it to try to account for the fact that there might be some entities  
from one partitioning on the same processor as the other partitioning.  
Right?

mark

On Dec 22, 2009, at 12:36 AM, Tim Tautges wrote:

> That is correct, and is the reason for using a completely different  
> one (and was the key element of the breakthough on parallel contact,  
> as I understand it).
>
> - tim
>
> Mark Beall wrote:
>> For the known examples of needing multiple partitionings is there  
>> generally any correlation between the partitions (meaning that  
>> entities in one partitioning end up on the same processors as  
>> entities in the other partitioning)? I assuming there is a very low  
>> correlation between the partitionings, almost by definition (since,  
>> otherwise, why have the other partitioning). Is that correct?
>> mark
>> On Dec 21, 2009, at 11:56 AM, Tim Tautges wrote:
>>> Interesting.  I've thought about PIC codes in the context, but  
>>> always wondered whether apps would consider it overkill to do the  
>>> particles with vertices (which I think is what you're implying  
>>> below?  Or not?)
>>>
>>> - tim
>>>
>>> Devine, Karen D wrote:
>>>> Thanks, Tim, for providing a good example.  Here's another:  a
>>>> particle-in-cell code can partition the mesh one way for force  
>>>> calculations
>>>> and a different way for particle calculations.  The force  
>>>> calculations use a
>>>> static partitioning; the particle calculations use a dynamic  
>>>> partitioning
>>>> that attempts to maintain particle balance.
>>>> Karen
>>>> On 12/18/09 9:54 AM, "Tim Tautges" <tautges at mcs.anl.gov> wrote:
>>>>> The best example, brought up by both Karen and me IIRC, is of
>>>>> large-deformation transient dynamics with contact, where
>>>>> the FE solution of the dynamics is solved on 3d elements on one  
>>>>> partition, and
>>>>> the contact solution is solved on faces
>>>>> on a different partition.  Many believe it was this capability  
>>>>> that made truly
>>>>> scalable parallel FEM with contact even
>>>>> possible.  See e.g.
>>>>>
>>>>> Transient dynamics simulations: parallel algorithms for contact  
>>>>> detection and
>>>>> smoothed particle hydrodynamics,
>>>>> Proceedings of the 1996 ACM/IEEE conference on Supercomputing,  
>>>>> 1996.
>>>>>
>>>>> That's just one reference, there are many others for that  
>>>>> particular work.
>>>>>
>>>>> I think the details of multiple *active* partitions still need  
>>>>> some work, both
>>>>> in use cases and in how they behave under
>>>>> iMeshP.  Normally I wouldn't advocate such an unexplored thing  
>>>>> being part of
>>>>> the initial interface definition, but in
>>>>> this case I think it's an important enough capability that it's  
>>>>> justified.
>>>>>
>>>>> - tim
>>>>>
>>>>> Mark Beall wrote:
>>>>>> As a more general context to the questions that Saurabh asked,  
>>>>>> the main
>>>>>> questions we have about iMeshP are issues related to having  
>>>>>> multiple
>>>>>> partitions. Although we won't be supporting that for now (since  
>>>>>> our
>>>>>> software doesn't support that), it would be helpful in  
>>>>>> understanding
>>>>>> that need if someone could give some examples of how this  
>>>>>> functionality
>>>>>> would be used.
>>>>>>
>>>>>> mark
>>>>>>
>>>>>>
>>>>> -- 
>>>>> ================================================================
>>>>> "You will keep in perfect peace him whose mind is
>>>>>  steadfast, because he trusts in you."               Isaiah 26:3
>>>>>
>>>>>             Tim Tautges            Argonne National Laboratory
>>>>>         (tautges at mcs.anl.gov)      (telecommuting from UW-Madison)
>>>>>         phone: (608) 263-8485      1500 Engineering Dr.
>>>>>           fax: (608) 263-4499      Madison, WI 53706
>>>>>
>>>>>
>>>>>
>>>
>>> -- 
>>> ================================================================
>>> "You will keep in perfect peace him whose mind is
>>> steadfast, because he trusts in you."               Isaiah 26:3
>>>
>>>            Tim Tautges            Argonne National Laboratory
>>>        (tautges at mcs.anl.gov)      (telecommuting from UW-Madison)
>>>        phone: (608) 263-8485      1500 Engineering Dr.
>>>          fax: (608) 263-4499      Madison, WI 53706
>>>
>
> -- 
> ================================================================
> "You will keep in perfect peace him whose mind is
>  steadfast, because he trusts in you."               Isaiah 26:3
>
>             Tim Tautges            Argonne National Laboratory
>         (tautges at mcs.anl.gov)      (telecommuting from UW-Madison)
>         phone: (608) 263-8485      1500 Engineering Dr.
>           fax: (608) 263-4499      Madison, WI 53706
>