Are there any plans to get the missing hook into PETSc for AIR? Just curious if there’s an issue I can subscribe to or anything.
(Independently I’m excited to test HPDDM out tomorrow) > On Apr 13, 2023, at 10:29 PM, Pierre Jolivet <pierre.joli...@lip6.fr> wrote: > > >> On 14 Apr 2023, at 7:02 AM, Alexander Lindsay <alexlindsay...@gmail.com> >> wrote: >> >> Pierre, >> >> This is very helpful information. Thank you. Yes I would appreciate those >> command line options if you’re willing to share! > > No problem, I’ll get in touch with you in private first, because it may > require some extra work (need a couple of extra options in PETSc > ./configure), and this is not very related to the problem at hand, so best > not to spam the mailing list. > > Thanks, > Pierre > >>>> On Apr 13, 2023, at 9:54 PM, Pierre Jolivet <pierre.joli...@lip6.fr> wrote: >>>> >>> >>> >>>> On 13 Apr 2023, at 10:33 PM, Alexander Lindsay <alexlindsay...@gmail.com> >>>> wrote: >>>> >>>> Hi, I'm trying to solve steady Navier-Stokes for different Reynolds >>>> numbers. My options table >>>> >>>> -dm_moose_fieldsplit_names u,p >>>> -dm_moose_nfieldsplits 2 >>>> -fieldsplit_p_dm_moose_vars pressure >>>> -fieldsplit_p_ksp_type preonly >>>> -fieldsplit_p_pc_type jacobi >>>> -fieldsplit_u_dm_moose_vars vel_x,vel_y >>>> -fieldsplit_u_ksp_type preonly >>>> -fieldsplit_u_pc_hypre_type boomeramg >>>> -fieldsplit_u_pc_type hypre >>>> -pc_fieldsplit_schur_fact_type full >>>> -pc_fieldsplit_schur_precondition selfp >>>> -pc_fieldsplit_type schur >>>> -pc_type fieldsplit >>>> >>>> works wonderfully for a low Reynolds number of 2.2. The solver performance >>>> crushes LU as I scale up the problem. However, not surprisingly this >>>> options table struggles when I bump the Reynolds number to 220. I've read >>>> that use of AIR (approximate ideal restriction) can improve performance >>>> for advection dominated problems. I've tried setting >>>> -pc_hypre_boomeramg_restriction_type 1 for a simple diffusion problem and >>>> the option works fine. However, when applying it to my field-split >>>> preconditioned Navier-Stokes system, I get immediate non-convergence: >>>> >>>> 0 Nonlinear |R| = 1.033077e+03 >>>> 0 Linear |R| = 1.033077e+03 >>>> Linear solve did not converge due to DIVERGED_NANORINF iterations 0 >>>> Nonlinear solve did not converge due to DIVERGED_LINEAR_SOLVE iterations 0 >>>> >>>> Does anyone have an idea as to why this might be happening? >>> >>> Do not use this option, even when not part of PCFIELDSPLIT. >>> There is some missing plumbing in PETSc which makes it unusable, see Ben’s >>> comment here >>> https://github.com/hypre-space/hypre/issues/764#issuecomment-1353452417. >>> In fact, it’s quite easy to make HYPRE generate NaN with a very simple >>> stabilized convection—diffusion problem near the pure convection limit >>> (something that ℓAIR is supposed to handle). >>> Even worse, you can make HYPRE fill your terminal with printf-style >>> debugging messages >>> https://github.com/hypre-space/hypre/blob/5546cc22d46b3dba253849f258786da47c9a7b21/src/parcsr_ls/par_lr_restr.c#L1416 >>> with this option turned on. >>> As a result, I have been unable to reproduce any of the ℓAIR results. >>> This also explains why I have been using plain BoomerAMG instead of ℓAIR >>> for the comparison in page 9 of https://arxiv.org/pdf/2201.02250.pdf (if >>> you would like to try the PC we are using, I could send you the command >>> line options). >>> >>> Thanks, >>> Pierre >>> >>>> If not, I'd take a suggestion on where to set a breakpoint to start my own >>>> investigation. Alternatively, I welcome other preconditioning suggestions >>>> for an advection dominated problem. >>>> >>>> Alex >>> >
