On Thu, Jan 28, 2016 at 1:37 PM, Dave May <[email protected]> wrote:
> > > On Thursday, 28 January 2016, Matthew Knepley <[email protected]> wrote: > >> On Thu, Jan 28, 2016 at 11:36 AM, Xiangdong <[email protected]> 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. >> > > Currently Telescope will only repartition 2d and 3d DMDA's. It > does perform data migration and allows users to specify the number of ranks > to be used in each I,j,k direction via -xxx_grid_x etc. I wouldn't say it > supports "load balancing", as there is no mechanism to define number of > points in each sub-domain > Let me be more precise. All I have suggested for any of this are redistribution tools. You will have to determine the right weights for "load balance", which I think is always true. Using the default weights is crazy. Matt > Cheers > Dave > > > >> >> Thanks, >> >> Matt >> >> >>> >>> Xiangdong >>> >>> On Thu, Jan 28, 2016 at 12:21 PM, Barry Smith <[email protected]> >>> wrote: >>> >>>> >>>> > On Jan 28, 2016, at 11:11 AM, Xiangdong <[email protected]> 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 <[email protected]> wrote: >>>> > Xiangdong <[email protected]> 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 >> > -- 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
