Can you clarify what you mean by null-space cleaning. I just run SOR on the coarse grid.
On Mon, Jul 9, 2012 at 11:52 AM, Mark F. Adams <mark.adams at columbia.edu>wrote: > > On Jul 9, 2012, at 12:39 PM, John Mousel wrote: > > Mark, > > The problem is indeed non-symmetric. We went back and forth in March about > this problem. I think we ended up concluding that the coarse size couldn't > get too small or the null-space presented problems. > > > Oh its singular. I forget what the issues were but an iterative coarse > grid solver should be fine for singular problems, perhaps with null space > cleaning if the kernel is sneaking in. Actually there is an SVD coarse > grid solver: > > -mg_coarse_pc_type svd > > That is the most robust. > > When I did get it to work, I tried to scale it up, and on my local > university cluster, it seemed to just hang when the core counts got above > something like 16 cores. I don't really trust that machine though. > > > That's the machine. GAMG does have some issues but I've not seen it hang. > > It's new and has been plagued by hardware incompatability issues since day > 1. I could re-examine this on Kraken. Also, what option are you talking > about with ML. I thought I had tried all the -pc_ml_CoarsenScheme options, > but I could be wrong. > > > This sounds like the right one. I try to be careful in my solvers to be > invariant to subdomain shapes and sizes and I think Ray Tuminaro (ML > developer) at least has options that should be careful about this also. > But I don't know much about what they are deploying these days. > > Mark > > > John > > > > On Mon, Jul 9, 2012 at 11:30 AM, Mark F. Adams <mark.adams at > columbia.edu>wrote: > >> What problems are you having again with GAMG? Are you problems >> unsymmetric? >> >> ML has several coarsening strategies available and I think the default >> does aggregation locally and does not aggregate across processor >> subdomains. If you have poorly shaped domains then you want to use a >> global coarsening method (these are not expensive). >> >> Mark >> >> On Jul 9, 2012, at 12:17 PM, John Mousel wrote: >> >> Mark, >> >> I still haven't had much luck getting GAMG to work consistently for my >> Poisson problem. ML seems to work nicely on low core counts, but I have a >> problem where I can get long thin portions of grid on some processors >> instead of nice block like chunks at high core counts, which leads to a >> pretty tough time for ML. >> >> John >> >> On Mon, Jul 9, 2012 at 10:58 AM, John Mousel <john.mousel at gmail.com>wrote: >> >>> Getting rid of the Hypre option seemed to be the trick. >>> >>> On Mon, Jul 9, 2012 at 10:40 AM, Mark F. Adams <mark.adams at >>> columbia.edu>wrote: >>> >>>> Google PTL_NO_SPACE and you will find some NERSC presentations on how >>>> to go about fixing this. (I have run into these problems years ago but >>>> forget the issues) >>>> >>>> Also, I would try running with a Jacobi solver to see if that fixes the >>>> problem. If so then you might try >>>> >>>> -pc_type gamg >>>> -pc_gamg_agg_nsmooths 1 >>>> -pc_gamg_type agg >>>> >>>> This is a built in AMG solver so perhaps it plays nicer with resources >>>> ... >>>> >>>> Mark >>>> >>>> On Jul 9, 2012, at 10:57 AM, John Mousel wrote: >>>> >>>> > I'm running on Kraken and am currently working with 4320 cores. I get >>>> the following error in KSPSolve. >>>> > >>>> > [2711]: >>>> (/ptmp/ulib/mpt/nightly/5.3/120211/mpich2/src/mpid/cray/src/adi/ptldev.c:2046) >>>> PtlMEInsert failed with error : PTL_NO_SPACE >>>> > MHV_exe: >>>> /ptmp/ulib/mpt/nightly/5.3/120211/mpich2/src/mpid/cray/src/adi/ptldev.c:2046: >>>> MPIDI_CRAY_ptldev_desc_pkt: Assertion `0' failed. >>>> > forrtl: error (76): Abort trap signal >>>> > Image PC Routine Line >>>> Source >>>> > MHV_exe 00000000014758CB Unknown Unknown >>>> Unknown >>>> > MHV_exe 000000000182ED43 Unknown Unknown >>>> Unknown >>>> > MHV_exe 0000000001829460 Unknown Unknown >>>> Unknown >>>> > MHV_exe 00000000017EDE3E Unknown Unknown >>>> Unknown >>>> > MHV_exe 00000000017B3FE6 Unknown Unknown >>>> Unknown >>>> > MHV_exe 00000000017B3738 Unknown Unknown >>>> Unknown >>>> > MHV_exe 00000000017B2B12 Unknown Unknown >>>> Unknown >>>> > MHV_exe 00000000017B428F Unknown Unknown >>>> Unknown >>>> > MHV_exe 000000000177FCE1 Unknown Unknown >>>> Unknown >>>> > MHV_exe 0000000001590A43 Unknown Unknown >>>> Unknown >>>> > MHV_exe 00000000014F909B Unknown Unknown >>>> Unknown >>>> > MHV_exe 00000000014FF53B Unknown Unknown >>>> Unknown >>>> > MHV_exe 00000000014A4E25 Unknown Unknown >>>> Unknown >>>> > MHV_exe 0000000001487D57 Unknown Unknown >>>> Unknown >>>> > MHV_exe 000000000147F726 Unknown Unknown >>>> Unknown >>>> > MHV_exe 000000000137A8D3 Unknown Unknown >>>> Unknown >>>> > MHV_exe 0000000000E97BF2 Unknown Unknown >>>> Unknown >>>> > MHV_exe 000000000098EAF1 Unknown Unknown >>>> Unknown >>>> > MHV_exe 0000000000989C20 Unknown Unknown >>>> Unknown >>>> > MHV_exe 000000000097A9C2 Unknown Unknown >>>> Unknown >>>> > MHV_exe 000000000082FF2D axbsolve_ 539 >>>> PetscObjectsOperations.F90 >>>> > >>>> > This is somewhere in KSPSolve. Is there an MPICH environment variable >>>> that needs tweaking? I couldn't really find much on this particular error. >>>> > The solver is BiCGStab with Hypre as a preconditioner. >>>> > >>>> > -ksp_type bcgsl -pc_type hypre -pc_hypre_type boomeramg -ksp_monitor >>>> > >>>> > Thanks, >>>> > >>>> > John >>>> >>>> >>> >> >> > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120709/04573f2f/attachment-0001.html>
