See src/snes/tutorials/ex70.c for the code that I think was used for that paper.
Alexander Lindsay <alexlindsay...@gmail.com> writes: > Sorry for the spam. Looks like these authors have published multiple papers > on the subject > > cover.jpg > Combining the Augmented Lagrangian Preconditioner with the Simple Schur > Complement Approximation | SIAM Journal on > Scientific Computingdoi.org > cover.jpg > > On Jul 28, 2023, at 12:59 PM, Alexander Lindsay <alexlindsay...@gmail.com> > wrote: > > Do you know of anyone who has applied the augmented Lagrange methodology to > a finite volume discretization? > > On Jul 6, 2023, at 6:25 PM, Matthew Knepley <knep...@gmail.com> wrote: > > On Thu, Jul 6, 2023 at 8:30 PM Alexander Lindsay <alexlindsay...@gmail.com> > wrote: > > This is an interesting article that compares a multi-level ILU algorithm to > approximate commutator and augmented > Lagrange methods: https://doi.org/10.1002/fld.5039 > > That is for incompressible NS. The results are not better than > https://arxiv.org/abs/1810.03315, and that PC is considerably > simpler and already implemented in PETSc. There is an update in to this > > > > https://epubs.siam.org/doi/abs/10.1137/21M1430698?casa_token=Fp_XhuZStZ0AAAAA:YDhnkW9XvAom_b8KocWz-hBEI7FAt46aw3ICa0FvCrOVCtYr9bwvtqJ4aBOTkDSvANKh6YTQEw > > > which removes the need for complicated elements. > > You might need stuff like ILU for compressible flow, but I think > incompressible is solved. > > Thanks, > > Matt > > On Wed, Jun 28, 2023 at 11:37 AM Alexander Lindsay > <alexlindsay...@gmail.com> wrote: > > I do believe that based off the results in https://doi.org/10.1137/040608817 > we should be able to make LSC, with > proper scaling, compare very favorably with PCD > > On Tue, Jun 27, 2023 at 10:41 AM Alexander Lindsay > <alexlindsay...@gmail.com> wrote: > > I've opened https://gitlab.com/petsc/petsc/-/merge_requests/6642 which adds > a couple more scaling > applications of the inverse of the diagonal of A > > On Mon, Jun 26, 2023 at 6:06 PM Alexander Lindsay <alexlindsay...@gmail.com> > wrote: > > I guess that similar to the discussions about selfp, the approximation of > the velocity mass matrix by the > diagonal of the velocity sub-matrix will improve when running a transient as > opposed to a steady > calculation, especially if the time derivative is lumped.... Just thinking > while typing > > On Mon, Jun 26, 2023 at 6:03 PM Alexander Lindsay <alexlindsay...@gmail.com> > wrote: > > Returning to Sebastian's question about the correctness of the current LSC > implementation: in the > taxonomy paper that Jed linked to (which talks about SIMPLE, PCD, and LSC), > equation 21 shows four > applications of the inverse of the velocity mass matrix. In the PETSc > implementation there are at > most two applications of the reciprocal of the diagonal of A (an > approximation to the velocity mass > matrix without more plumbing, as already pointed out). It seems like for > code implementations in > which there are possible scaling differences between the velocity and > pressure equations, that this > difference in the number of inverse applications could be significant? I > know Jed said that these > scalings wouldn't really matter if you have a uniform grid, but I'm not 100% > convinced yet. > > I might try fiddling around with adding two more reciprocal applications. > > On Fri, Jun 23, 2023 at 1:09 PM Pierre Jolivet <pierre.joli...@lip6.fr> > wrote: > > On 23 Jun 2023, at 10:06 PM, Pierre Jolivet <pierre.joli...@lip6.fr> wrote: > > On 23 Jun 2023, at 9:39 PM, Alexander Lindsay <alexlindsay...@gmail.com> > wrote: > > Ah, I see that if I use Pierre's new 'full' option for > -mat_schur_complement_ainv_type > > That was not initially done by me > > Oops, sorry for the noise, looks like it was done by me indeed in > 9399e4fd88c6621aad8fe9558ce84df37bd6fada… > > Thanks, > Pierre > > (though I recently tweaked MatSchurComplementComputeExplicitOperator() a bit > to use > KSPMatSolve(), so that if you have a small Schur complement — which is not > really the case > for NS — this could be a viable option, it was previously painfully slow). > > Thanks, > Pierre > > that I get a single iteration for the Schur complement solve with LU. That's > a nice testing > option > > On Fri, Jun 23, 2023 at 12:02 PM Alexander Lindsay <alexlindsay...@gmail.com> > wrote: > > I guess it is because the inverse of the diagonal form of A00 becomes a poor > representation of the inverse of A00? I guess naively I would have thought > that the > blockdiag form of A00 is A00 > > On Fri, Jun 23, 2023 at 10:18 AM Alexander Lindsay <alexlindsay...@gmail.com> > wrote: > > Hi Jed, I will come back with answers to all of your questions at some > point. I > mostly just deal with MOOSE users who come to me and tell me their solve is > converging slowly, asking me how to fix it. So I generally assume they have > built an appropriate mesh and problem size for the problem they want to solve > and added appropriate turbulence modeling (although my general assumption > is often violated). > > > And to confirm, are you doing a nonlinearly implicit velocity-pressure > solve? > > Yes, this is our default. > > A general question: it seems that it is well known that the quality of selfp > degrades with increasing advection. Why is that? > > On Wed, Jun 7, 2023 at 8:01 PM Jed Brown <j...@jedbrown.org> wrote: > > Alexander Lindsay <alexlindsay...@gmail.com> writes: > > > This has been a great discussion to follow. Regarding > > > >> when time stepping, you have enough mass matrix that cheaper > preconditioners are good enough > > > > I'm curious what some algebraic recommendations might be for high Re > in > > transients. > > What mesh aspect ratio and streamline CFL number? Assuming your model > is turbulent, can you say anything about momentum thickness Reynolds > number Re_θ? What is your wall normal spacing in plus units? (Wall > resolved or wall modeled?) > > And to confirm, are you doing a nonlinearly implicit velocity-pressure > solve? > > > I've found one-level DD to be ineffective when applied monolithically or > to the momentum block of a split, as it scales with the mesh size. > > I wouldn't put too much weight on "scaling with mesh size" per se. You > want an efficient solver for the coarsest mesh that delivers sufficient > accuracy in your flow regime. Constants matter. > > Refining the mesh while holding time steps constant changes the advective > CFL number as well as cell Peclet/cell Reynolds numbers. A meaningful > scaling study is to increase Reynolds number (e.g., by growing the domain) > while keeping mesh size matched in terms of plus units in the viscous > sublayer and Kolmogorov length in the outer boundary layer. That turns > out to not be a very automatic study to do, but it's what matters and you > can spend a lot of time chasing ghosts with naive scaling studies. > > -- > 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 > > https://www.cse.buffalo.edu/~knepley/
