[petsc-dev] DMFOREST repartitioning in PETSc

[Saurabh Chawdhary]

Thank you Tobin. I was actually more interested in repartitioning after 
the mesh has been dynamically changed (say, after refinement in certain 
portions of mesh).


On 03/22/2018 07:10 AM, Tobin Isaac wrote:
>
> On March 21, 2018 11:26:35 AM MDT, Saurabh Chawdhary <schawdhary at anl.gov> wrote:
>> Hello team,
>>
>> I haven't used petsc since DMFOREST was released but I have a question
>> regarding repartitioning of DMFOREST mesh. How is the repartitioning of
>>
>> mesh over processors done after some mesh refinement is carried out? Is
>>
>> it done by calling a p4est function or partitioning is done in PETSc?
>>
>> I was using p4est (natively) a couple of years ago and I remember that
>> when I tried to partition the grid I could only use the serial METIS
>> and
>> not the parMETIS with p4est (using a native function
>> /p4est_connectivity_reorder/). So what I want to know is whether
>> DMFOREST repartitioning is done in parallel or in serial?
> You can use the following workflow:
>
> - Create/read-only an unstructured hexahedral mesh as a DMPlex
> - Use ParMETIS to repartition that: there is a ParMETIS implementation of PetscPartitioner, which creates index sets and communication patterns for DMPlexDistribute.
> - Convert the DMPlex to DMP4est or DMP8est.
>
> This does not avoid the fundamental limitations of p4est: the distributed mesh will be redundantly serialized behind-the-scenes, and the coarse-mesh ordering derived from ParMETIS will be static for the life of the forest mesh.
I am not sure I understand how the distributed mesh is redundantly 
serialized in p4est. Do you mean that the partitioning is done serially?
>
>>
>> Thank you.
>>
>> Saurabh