Here are the three logs. FGMRES also gives a wrong first iterate. I think Mark was right in the sense that the problem is _most likely_ in my RHS. But I need to figure out why I only get this problem with right-preconditioned KSPs with restrict or none.
Thanks, Pierre
dump-basic
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dump-none
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dump-restrict
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> On 13 Oct 2019, at 8:16 PM, Smith, Barry F. <bsm...@mcs.anl.gov> wrote: > > > Is this one process with one subdomain? (And hence no meaningful overlap > since there is nothing to overlap?) And you expect to get the "exact" answer > on one iteration? > > Please run the right preconditioned GMRES with -pc_asm_type [restrict and > basic and none] -ksp_monitor_true_solution and send the output for the > three cases. > > For kicks you can also try FGMRES (which always uses right preconditioning) > to see if the same problem appears. > > Barry > > >> On Oct 13, 2019, at 2:41 AM, Pierre Jolivet via petsc-dev >> <petsc-dev@mcs.anl.gov> wrote: >> >> Hello, >> I’m struggling to understand the following weirdness with PCASM with exact >> subdomain solvers. >> I’m dealing with a very simple Poisson problem with Dirichlet + Neumann BCs. >> If I use PCBJACOBI + KSPPREONLY or 1 iteration of GMRES either >> preconditioned on the right or on the left, I get the expected result, cf. >> attached screenshot. >> If I use PCASM + KSPPREONLY or 1 iteration of GMRES preconditioned on the >> left, I get the expected result as well. >> However, with PCASM + 1 iteration of GMRES preconditioned on the right, I >> don’t get what I should (I believe). >> Furthermore, this problem is specific to -pc_asm_type restrict,none (I get >> the expected result with basic,interpolate). >> >> Any hint? >> >> Thanks, >> Pierre >> >> $ -sub_pc_type lu -ksp_max_it 1 -ksp_type gmres -pc_type bjacobi >> -ksp_pc_side right -> bjacobi_OK >> $ -sub_pc_type lu -ksp_max_it 1 -ksp_type gmres -pc_type asm -ksp_pc_side >> left -> asm_OK >> $ -sub_pc_type lu -ksp_max_it 1 -ksp_type gmres -pc_type asm -ksp_pc_side >> right -> asm_KO >> >> <bjacobi_OK.png><asm_OK.png><asm_KO.png> >
