[petsc-users] repartition for dynamic load balancing

[Matthew Knepley]

On Thu, Jan 28, 2016 at 11:36 AM, Xiangdong <epscodes at gmail.com> wrote:

> What functions/tools can I use for dynamic migration in DMPlex framework?
>

In this paper, http://arxiv.org/abs/1506.06194, we explain how to use the
DMPlexMigrate() function to redistribute data.
In the future, its likely we will add a function that wraps it up with
determination of the new partition at the same time.


> Can you also name some external mesh management systems? Thanks.
>

I will note that if load balance in the solve is your only concern,
PCTelescope can redistribute the DMDA solve.

  Thanks,

    Matt


>
> Xiangdong
>
> On Thu, Jan 28, 2016 at 12:21 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:
>
>>
>> > On Jan 28, 2016, at 11:11 AM, Xiangdong <epscodes at gmail.com> wrote:
>> >
>> > Yes, it can be either DMDA or DMPlex. For example, I have 1D DMDA with
>> Nx=10 and np=2. At the beginning each processor owns 5 cells. After some
>> simulation time, I found that repartition the 10 cells into 3 and 7 is
>> better for load balancing. Is there an easy/efficient way to migrate data
>> from one partition to another partition? I am wondering whether there are
>> some functions or libraries help me manage this redistribution.
>>
>>   For DMDA we don't provide tools for doing this, nor do we expect to.
>> For this type of need for dynamic migration we recommend using DMPlex or
>> some external mesh management system.
>>
>>   Barry
>>
>> >
>> > Thanks.
>> > Xiangdong
>> >
>> > On Thu, Jan 28, 2016 at 12:20 AM, Jed Brown <jed at jedbrown.org> wrote:
>> > Xiangdong <epscodes at gmail.com> writes:
>> >
>> > > I have a question on dynamic load balance in petsc. I started running
>> a
>> > > simulation with one partition. As the simulation goes on, that
>> partition
>> > > may lead to load imbalance since it is a non-steady problem. If it is
>> worth
>> > > to perform the load balance, is there an easy way to re-partition the
>> mesh
>> > > and continue the simulation?
>> >
>> > Are you using a PETSc DM?  What "mesh"?  If you own it, then
>> > repartitioning it is entirely your business.
>> >
>> > In general, after adapting the mesh, you rebuild all algebraic data
>> > structures.  Solvers can be reset (SNESReset, etc.).
>> >
>>
>>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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