Pierre, This is very helpful information. Thank you. Yes I would appreciate those command line options if you’re willing to share!
> On Apr 13, 2023, at 9:54 PM, Pierre Jolivet <[email protected]> wrote: > > > >>> On 13 Apr 2023, at 10:33 PM, Alexander Lindsay <[email protected]> >>> 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 >
