On Thu, May 12, 2022 at 1:03 PM Takahashi, Tadanaga <[email protected]> wrote:
> Thank you for the feedback. We figured out what was causing the issue. We > were using DMGetBoundingBox > <https://petsc.org/main/docs/manualpages/DM/DMGetBoundingBox/> in order > to get the limits of the global domain, but gmin and gmax contained limits > for the local subdomains when we ran the code with NASM. Hence, our local > coordinates xi and yj were completely wrong. The documentation states > that DMGetBoundingBox gets the global limits. I believe this is a mistake. > I think I can explain this, and maybe you can tell us how to improve the documentation. I believe we make a new DM that comprises only the subdomain. Then the bounding box for this subdomain will only contain itself, not the original domain. Where should we say this? Thanks, Matt > This is our new output: > $ mpiexec -n 4 ./test1 -t1_N 20 -snes_max_it 50 -snes_monitor -snes_view > -da_overlap 3 -snes_type nasm -snes_nasm_type restrict > 0 SNES Function norm 7.244681057908e+02 > 1 SNES Function norm 4.394913250889e+01 > 2 SNES Function norm 1.823326663029e+01 > 3 SNES Function norm 7.033938512358e+00 > 4 SNES Function norm 2.797351504285e+00 > 5 SNES Function norm 1.130613777736e+00 > 6 SNES Function norm 4.605418417192e-01 > 7 SNES Function norm 1.882307001920e-01 > 8 SNES Function norm 7.704148683921e-02 > 9 SNES Function norm 3.155090858782e-02 > 10 SNES Function norm 1.292418188473e-02 > 11 SNES Function norm 5.294645671797e-03 > 12 SNES Function norm 2.169143207557e-03 > 13 SNES Function norm 8.886826738192e-04 > 14 SNES Function norm 3.640894847145e-04 > 15 SNES Function norm 1.491663153414e-04 > 16 SNES Function norm 6.111303899450e-05 > 17 SNES Function norm 2.503785968501e-05 > 18 SNES Function norm 1.025795062417e-05 > 19 SNES Function norm 4.202657921479e-06 > SNES Object: 4 MPI processes > type: nasm > total subdomain blocks = 4 > Local solver information for first block on rank 0: > Use -snes_view ::ascii_info_detail to display information for all > blocks > SNES Object: (sub_) 1 MPI processes > type: newtonls > maximum iterations=50, maximum function evaluations=10000 > tolerances: relative=1e-08, absolute=1e-50, solution=1e-08 > total number of linear solver iterations=2 > total number of function evaluations=3 > norm schedule ALWAYS > Jacobian is built using a DMDA local Jacobian > SNESLineSearch Object: (sub_) 1 MPI processes > type: bt > interpolation: cubic > alpha=1.000000e-04 > maxstep=1.000000e+08, minlambda=1.000000e-12 > tolerances: relative=1.000000e-08, absolute=1.000000e-15, > lambda=1.000000e-08 > maximum iterations=40 > KSP Object: (sub_) 1 MPI processes > type: preonly > maximum iterations=10000, initial guess is zero > tolerances: relative=1e-05, absolute=1e-50, divergence=10000. > left preconditioning > using NONE norm type for convergence test > PC Object: (sub_) 1 MPI processes > type: lu > out-of-place factorization > tolerance for zero pivot 2.22045e-14 > matrix ordering: nd > factor fill ratio given 5., needed 2.13732 > Factored matrix follows: > Mat Object: 1 MPI processes > type: seqaij > rows=169, cols=169 > package used to perform factorization: petsc > total: nonzeros=13339, allocated nonzeros=13339 > using I-node routines: found 104 nodes, limit used is 5 > linear system matrix = precond matrix: > Mat Object: 1 MPI processes > type: seqaij > rows=169, cols=169 > total: nonzeros=6241, allocated nonzeros=6241 > total number of mallocs used during MatSetValues calls=0 > not using I-node routines > maximum iterations=50, maximum function evaluations=10000 > tolerances: relative=1e-08, absolute=1e-50, solution=1e-08 > total number of function evaluations=20 > norm schedule ALWAYS > Jacobian is built using a DMDA local Jacobian > problem ex10 on 20 x 20 point 2D grid with d = 3, and eps = 0.082: > error |u-uexact|_inf = 2.879e-02, |u-uexact|_h = 1.707e-02 > > On Thu, May 12, 2022 at 9:37 AM Matthew Knepley <[email protected]> wrote: > >> Your subdomain solves do not appear to be producing descent whatsoever. >> Possible reasons: >> >> 1) Your subdomain Jacobians are wrong (this is usually the problem) >> >> 2) You have some global coupling field for which local solves give no >> descent. (For this you want nonlinear elimination I think) >> >> Thanks, >> >> Matt >> >> On Thu, May 12, 2022 at 9:02 AM Takahashi, Tadanaga <[email protected]> >> wrote: >> >>> I ran the code with the additional options but the raw output is about >>> 75,000 lines. I cannot paste it directly in the email. The output is in the >>> attached file. >>> >>> On Wed, May 11, 2022 at 11:44 PM Jed Brown <[email protected]> wrote: >>> >>>> Can you add -snes_linesearch_monitor -sub_snes_linesearch_monitor >>>> -ksp_converged_reason and send the output?? >>>> >>>> "Takahashi, Tadanaga" <[email protected]> writes: >>>> >>>> > Hello, >>>> > >>>> > We are working on a finite difference solver for a 2D nonlinear PDE >>>> with >>>> > Dirichlet Boundary conditions on a rectangular domain. Our goal is to >>>> solve >>>> > the problem with parallel nonlinear additive Schwarz (NASM) as the >>>> outer >>>> > solver. Our code is similar to SNES example 5 >>>> > <https://petsc.org/release/src/snes/tutorials/ex5.c.html>. In >>>> example 5, >>>> > the parallel NASM can be executed with a command like `mpiexec -n 4 >>>> ./ex5 >>>> > -mms 3 -snes_type nasm -snes_nasm_type restrict -da_overlap 2` which >>>> gives >>>> > a convergent result. We assume this is the correct usage. A comment >>>> in the >>>> > source code for NASM mentions that NASM should be a preconditioner but >>>> > there's no documentation on the usage. The Brune paper does not cover >>>> > parallel NASM either. We observed that increasing the overlap leads to >>>> > fewer Schwarz iterations. The parallelization works seamlessly for an >>>> > arbitrary number of subdomains. This is the type of behavior we were >>>> > expecting from our code. >>>> > >>>> > Our method uses box-style stencil width d = ceil(N^(1/3)) on a N by N >>>> DMDA. >>>> > The finite difference stencil consists of 4d+1 points spread out in a >>>> > diamond formation. If a stencil point is out of bounds, then it is >>>> > projected onto the boundary curve. Since the nodes on the boundary >>>> curve >>>> > would result in an irregular mesh, we chose not treat boundary nodes >>>> as >>>> > unknowns as in Example 5. We use DMDACreate2d to create the DA for the >>>> > interior points and DMDASNESSetFunctionLocal to associate the residue >>>> > function to the SNES object. >>>> > >>>> > Our code works serially. We have also tested our code >>>> > with Newton-Krylov-Schwarz (NKS) by running something akin to >>>> `mpiexec -n >>>> > <n> ./solve -snes_type newtonls`. We have tested the NKS for several >>>> > quantities of subdomains and overlap and the code works as expected. >>>> We >>>> > have some confidence in the correctness of our code. The overlapping >>>> NASM >>>> > was implemented in MATLAB so we know the method converges. However, >>>> the >>>> > parallel NASM will not converge with our PETSc code. We don't >>>> understand >>>> > why NKS works while NASM does not. The F-norm residue monotonically >>>> > decreases and then stagnates. >>>> > >>>> > Here is an example of the output when attempting to run NASM in >>>> parallel: >>>> > takahashi@ubuntu:~/Desktop/MA-DDM/Cpp/Rectangle$ mpiexec -n 4 >>>> ./test1 -t1_N >>>> > 20 -snes_max_it 50 -snes_monitor -snes_view -da_overlap 3 -snes_type >>>> nasm >>>> > -snes_nasm_type restrict >>>> > 0 SNES Function norm 7.244681057908e+02 >>>> > 1 SNES Function norm 1.237688062971e+02 >>>> > 2 SNES Function norm 1.068926073552e+02 >>>> > 3 SNES Function norm 1.027563237834e+02 >>>> > 4 SNES Function norm 1.022184806736e+02 >>>> > 5 SNES Function norm 1.020818227640e+02 >>>> > 6 SNES Function norm 1.020325629121e+02 >>>> > 7 SNES Function norm 1.020149036595e+02 >>>> > 8 SNES Function norm 1.020088110545e+02 >>>> > 9 SNES Function norm 1.020067198030e+02 >>>> > 10 SNES Function norm 1.020060034469e+02 >>>> > 11 SNES Function norm 1.020057582380e+02 >>>> > 12 SNES Function norm 1.020056743241e+02 >>>> > 13 SNES Function norm 1.020056456101e+02 >>>> > 14 SNES Function norm 1.020056357849e+02 >>>> > 15 SNES Function norm 1.020056324231e+02 >>>> > 16 SNES Function norm 1.020056312727e+02 >>>> > 17 SNES Function norm 1.020056308791e+02 >>>> > 18 SNES Function norm 1.020056307444e+02 >>>> > 19 SNES Function norm 1.020056306983e+02 >>>> > 20 SNES Function norm 1.020056306826e+02 >>>> > 21 SNES Function norm 1.020056306772e+02 >>>> > 22 SNES Function norm 1.020056306753e+02 >>>> > 23 SNES Function norm 1.020056306747e+02 >>>> > 24 SNES Function norm 1.020056306745e+02 >>>> > 25 SNES Function norm 1.020056306744e+02 >>>> > 26 SNES Function norm 1.020056306744e+02 >>>> > 27 SNES Function norm 1.020056306744e+02 >>>> > 28 SNES Function norm 1.020056306744e+02 >>>> > 29 SNES Function norm 1.020056306744e+02 >>>> > 30 SNES Function norm 1.020056306744e+02 >>>> > 31 SNES Function norm 1.020056306744e+02 >>>> > 32 SNES Function norm 1.020056306744e+02 >>>> > 33 SNES Function norm 1.020056306744e+02 >>>> > 34 SNES Function norm 1.020056306744e+02 >>>> > 35 SNES Function norm 1.020056306744e+02 >>>> > 36 SNES Function norm 1.020056306744e+02 >>>> > 37 SNES Function norm 1.020056306744e+02 >>>> > 38 SNES Function norm 1.020056306744e+02 >>>> > 39 SNES Function norm 1.020056306744e+02 >>>> > 40 SNES Function norm 1.020056306744e+02 >>>> > 41 SNES Function norm 1.020056306744e+02 >>>> > 42 SNES Function norm 1.020056306744e+02 >>>> > 43 SNES Function norm 1.020056306744e+02 >>>> > 44 SNES Function norm 1.020056306744e+02 >>>> > 45 SNES Function norm 1.020056306744e+02 >>>> > 46 SNES Function norm 1.020056306744e+02 >>>> > 47 SNES Function norm 1.020056306744e+02 >>>> > 48 SNES Function norm 1.020056306744e+02 >>>> > 49 SNES Function norm 1.020056306744e+02 >>>> > 50 SNES Function norm 1.020056306744e+02 >>>> > SNES Object: 4 MPI processes >>>> > type: nasm >>>> > total subdomain blocks = 4 >>>> > Local solver information for first block on rank 0: >>>> > Use -snes_view ::ascii_info_detail to display information for all >>>> blocks >>>> > SNES Object: (sub_) 1 MPI processes >>>> > type: newtonls >>>> > maximum iterations=50, maximum function evaluations=10000 >>>> > tolerances: relative=1e-08, absolute=1e-50, solution=1e-08 >>>> > total number of linear solver iterations=22 >>>> > total number of function evaluations=40 >>>> > norm schedule ALWAYS >>>> > Jacobian is built using a DMDA local Jacobian >>>> > SNESLineSearch Object: (sub_) 1 MPI processes >>>> > type: bt >>>> > interpolation: cubic >>>> > alpha=1.000000e-04 >>>> > maxstep=1.000000e+08, minlambda=1.000000e-12 >>>> > tolerances: relative=1.000000e-08, absolute=1.000000e-15, >>>> > lambda=1.000000e-08 >>>> > maximum iterations=40 >>>> > KSP Object: (sub_) 1 MPI processes >>>> > type: preonly >>>> > maximum iterations=10000, initial guess is zero >>>> > tolerances: relative=1e-05, absolute=1e-50, divergence=10000. >>>> > left preconditioning >>>> > using NONE norm type for convergence test >>>> > PC Object: (sub_) 1 MPI processes >>>> > type: lu >>>> > out-of-place factorization >>>> > tolerance for zero pivot 2.22045e-14 >>>> > matrix ordering: nd >>>> > factor fill ratio given 5., needed 2.13732 >>>> > Factored matrix follows: >>>> > Mat Object: 1 MPI processes >>>> > type: seqaij >>>> > rows=169, cols=169 >>>> > package used to perform factorization: petsc >>>> > total: nonzeros=13339, allocated nonzeros=13339 >>>> > using I-node routines: found 104 nodes, limit used >>>> is 5 >>>> > linear system matrix = precond matrix: >>>> > Mat Object: 1 MPI processes >>>> > type: seqaij >>>> > rows=169, cols=169 >>>> > total: nonzeros=6241, allocated nonzeros=6241 >>>> > total number of mallocs used during MatSetValues calls=0 >>>> > not using I-node routines >>>> > maximum iterations=50, maximum function evaluations=10000 >>>> > tolerances: relative=1e-08, absolute=1e-50, solution=1e-08 >>>> > total number of function evaluations=51 >>>> > norm schedule ALWAYS >>>> > Jacobian is built using a DMDA local Jacobian >>>> > problem ex10 on 20 x 20 point 2D grid with d = 3, and eps = 0.082: >>>> > error |u-uexact|_inf = 3.996e-01, |u-uexact|_h = 2.837e-01 >>>> > >>>> > We have been stuck on this for a while now. We do not know how to >>>> debug >>>> > this issue. Please let us know if you have any insights. >>>> >>> >> >> -- >> 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/ >> <http://www.cse.buffalo.edu/~knepley/> >> > -- 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/ <http://www.cse.buffalo.edu/~knepley/>
