Use -pc_fieldsplit_0_ksp_type preonly
> On May 23, 2024, at 12:43 PM, Colton Bryant > <[email protected]> wrote: > > That produces the following error: > > [0]PETSC ERROR: Residual norm computed by GMRES recursion formula 2.79175e-07 > is far from the computed residual norm 0.000113154 at restart, residual norm > at start of cycle 2.83065e-07 > [0]PETSC ERROR: See > https://urldefense.us/v3/__https://petsc.org/release/faq/__;!!G_uCfscf7eWS!ZtDgFFlCg0V07VVhElstTyhYk7k_JOhZDT-XmG5SH94V00fLNgdy0Xm3HtempNQntM8S8XI0Eu8wDU5B5c7nyAk$ > for trouble shooting. > [0]PETSC ERROR: Petsc Release Version 3.21.0, unknown > [0]PETSC ERROR: ./mainOversetLS_exe on a arch-linux-c-opt named glass by > colton Thu May 23 10:41:09 2024 > [0]PETSC ERROR: Configure options --download-mpich --with-cc=gcc > --with-cxx=g++ --with-debugging=no --with-fc=gfortran COPTFLAGS=-O3 > CXXOPTFLAGS=-O3 FOPTFLAGS=-O3 PETSC_ARCH=arch-linux-c-opt --download-sowing > [0]PETSC ERROR: #1 KSPGMRESCycle() at > /home/colton/petsc/src/ksp/ksp/impls/gmres/gmres.c:115 > [0]PETSC ERROR: #2 KSPSolve_GMRES() at > /home/colton/petsc/src/ksp/ksp/impls/gmres/gmres.c:227 > [0]PETSC ERROR: #3 KSPSolve_Private() at > /home/colton/petsc/src/ksp/ksp/interface/itfunc.c:905 > [0]PETSC ERROR: #4 KSPSolve() at > /home/colton/petsc/src/ksp/ksp/interface/itfunc.c:1078 > [0]PETSC ERROR: #5 PCApply_FieldSplit_Schur() at > /home/colton/petsc/src/ksp/pc/impls/fieldsplit/fieldsplit.c:1203 > [0]PETSC ERROR: #6 PCApply() at > /home/colton/petsc/src/ksp/pc/interface/precon.c:497 > [0]PETSC ERROR: #7 KSP_PCApply() at > /home/colton/petsc/include/petsc/private/kspimpl.h:409 > [0]PETSC ERROR: #8 KSPFGMRESCycle() at > /home/colton/petsc/src/ksp/ksp/impls/gmres/fgmres/fgmres.c:123 > [0]PETSC ERROR: #9 KSPSolve_FGMRES() at > /home/colton/petsc/src/ksp/ksp/impls/gmres/fgmres/fgmres.c:235 > [0]PETSC ERROR: #10 KSPSolve_Private() at > /home/colton/petsc/src/ksp/ksp/interface/itfunc.c:905 > [0]PETSC ERROR: #11 KSPSolve() at > /home/colton/petsc/src/ksp/ksp/interface/itfunc.c:1078 > [0]PETSC ERROR: #12 solveStokes() at cartesianStokesGrid.cpp:1403 > > > > On Thu, May 23, 2024 at 10:33 AM Barry Smith <[email protected] > <mailto:[email protected]>> wrote: >> >> Run the failing case with also -ksp_error_if_not_converged so we see >> exactly where the problem is first detected. >> >> >> >> >>> On May 23, 2024, at 11:51 AM, Colton Bryant >>> <[email protected] >>> <mailto:[email protected]>> wrote: >>> >>> Hi Barry, >>> >>> Thanks for letting me know about the need to use fgmres in this case. I ran >>> a smaller problem (1230 in the first block) and saw similar behavior in the >>> true residual. >>> >>> I also ran the same problem with the options -fieldsplit_0_pc_type svd >>> -fieldsplit_0_pc_svd_monitor and get the following output: >>> SVD: condition number 1.933639985881e+03, 0 of 1230 singular values >>> are (nearly) zero >>> SVD: smallest singular values: 4.132036392141e-03 4.166444542385e-03 >>> 4.669534028645e-03 4.845532162256e-03 5.047038625390e-03 >>> SVD: largest singular values : 7.947990616611e+00 7.961437414477e+00 >>> 7.961851612473e+00 7.971335373142e+00 7.989870790960e+00 >>> >>> I would be surprised if the A_{00} block is ill conditioned as it's just a >>> standard discretization of the laplacian with some rows replaced with ones >>> on the diagonal due to interpolations from the overset mesh. I'm wondering >>> if I'm somehow violating a solvability condition of the problem? >>> >>> Thanks for the help! >>> >>> -Colton >>> >>> On Wed, May 22, 2024 at 6:09 PM Barry Smith <[email protected] >>> <mailto:[email protected]>> wrote: >>>> >>>> Thanks for the info. I see you are using GMRES inside the Schur >>>> complement solver, this is ok but when you do you need to use fgmres as >>>> the outer solver. But this is unlikely to be the cause of the exact >>>> problem you are seeing. >>>> >>>> I'm not sure why the Schur complement KSP is suddenly seeing a large >>>> increase in the true residual norm. Is it possible the A_{00} block is >>>> ill-conditioned? >>>> >>>> Can you run with a smaller problem? Say 2,000 or so in the first block? >>>> Is there still a problem? >>>> >>>> >>>> >>>> >>>> >>>>> On May 22, 2024, at 6:00 PM, Colton Bryant >>>>> <[email protected] >>>>> <mailto:[email protected]>> wrote: >>>>> >>>>> Hi Barry, >>>>> >>>>> I have not used any other solver parameters in the code and the full set >>>>> of solver related command line options are those I mentioned in the >>>>> previous email. >>>>> >>>>> Below is the output from -ksp_view: >>>>> >>>>> KSP Object: (back_) 1 MPI process >>>>> type: gmres >>>>> restart=30, using Classical (unmodified) Gram-Schmidt >>>>> Orthogonalization with no iterative refinement >>>>> happy breakdown tolerance 1e-30 >>>>> maximum iterations=10000, initial guess is zero >>>>> tolerances: relative=1e-08, absolute=1e-50, divergence=10000. >>>>> left preconditioning >>>>> using PRECONDITIONED norm type for convergence test >>>>> PC Object: (back_) 1 MPI process >>>>> type: fieldsplit >>>>> FieldSplit with Schur preconditioner, blocksize = 1, factorization >>>>> FULL >>>>> Preconditioner for the Schur complement formed from S itself >>>>> Split info: >>>>> Split number 0 Defined by IS >>>>> Split number 1 Defined by IS >>>>> KSP solver for A00 block >>>>> KSP Object: (back_fieldsplit_0_) 1 MPI process >>>>> type: gmres >>>>> restart=30, using Classical (unmodified) Gram-Schmidt >>>>> Orthogonalization with no iterative refinement >>>>> happy breakdown tolerance 1e-30 >>>>> maximum iterations=10000, initial guess is zero >>>>> tolerances: relative=1e-05, absolute=1e-50, divergence=10000. >>>>> left preconditioning >>>>> using PRECONDITIONED norm type for convergence test >>>>> PC Object: (back_fieldsplit_0_) 1 MPI process >>>>> type: lu >>>>> out-of-place factorization >>>>> tolerance for zero pivot 2.22045e-14 >>>>> matrix ordering: nd >>>>> factor fill ratio given 5., needed 8.83482 >>>>> Factored matrix follows: >>>>> Mat Object: (back_fieldsplit_0_) 1 MPI process >>>>> type: seqaij >>>>> rows=30150, cols=30150 >>>>> package used to perform factorization: petsc >>>>> total: nonzeros=2649120, allocated nonzeros=2649120 >>>>> using I-node routines: found 15019 nodes, limit used is >>>>> 5 >>>>> linear system matrix = precond matrix: >>>>> Mat Object: (back_fieldsplit_0_) 1 MPI process >>>>> type: seqaij >>>>> rows=30150, cols=30150 >>>>> total: nonzeros=299850, allocated nonzeros=299850 >>>>> total number of mallocs used during MatSetValues calls=0 >>>>> using I-node routines: found 15150 nodes, limit used is 5 >>>>> KSP solver for S = A11 - A10 inv(A00) A01 >>>>> KSP Object: (back_fieldsplit_1_) 1 MPI process >>>>> type: gmres >>>>> restart=30, using Classical (unmodified) Gram-Schmidt >>>>> Orthogonalization with no iterative refinement >>>>> happy breakdown tolerance 1e-30 >>>>> maximum iterations=10000, initial guess is zero >>>>> tolerances: relative=1e-08, absolute=1e-50, divergence=10000. >>>>> left preconditioning >>>>> using PRECONDITIONED norm type for convergence test >>>>> PC Object: (back_fieldsplit_1_) 1 MPI process >>>>> type: none >>>>> linear system matrix = precond matrix: >>>>> Mat Object: (back_fieldsplit_1_) 1 MPI process >>>>> type: schurcomplement >>>>> rows=15000, cols=15000 >>>>> Schur complement A11 - A10 inv(A00) A01 >>>>> A11 >>>>> Mat Object: (back_fieldsplit_1_) 1 MPI process >>>>> type: seqaij >>>>> rows=15000, cols=15000 >>>>> total: nonzeros=74700, allocated nonzeros=74700 >>>>> total number of mallocs used during MatSetValues calls=0 >>>>> not using I-node routines >>>>> A10 >>>>> Mat Object: 1 MPI process >>>>> type: seqaij >>>>> rows=15000, cols=30150 >>>>> total: nonzeros=149550, allocated nonzeros=149550 >>>>> total number of mallocs used during MatSetValues calls=0 >>>>> not using I-node routines >>>>> KSP solver for A00 block viewable with the additional option >>>>> -back_fieldsplit_0_ksp_view >>>>> A01 >>>>> Mat Object: 1 MPI process >>>>> type: seqaij >>>>> rows=30150, cols=15000 >>>>> total: nonzeros=149550, allocated nonzeros=149550 >>>>> total number of mallocs used during MatSetValues calls=0 >>>>> using I-node routines: found 15150 nodes, limit used is >>>>> 5 >>>>> linear system matrix = precond matrix: >>>>> Mat Object: (back_) 1 MPI process >>>>> type: seqaij >>>>> rows=45150, cols=45150 >>>>> total: nonzeros=673650, allocated nonzeros=673650 >>>>> total number of mallocs used during MatSetValues calls=0 >>>>> has attached null space >>>>> using I-node routines: found 15150 nodes, limit used is 5 >>>>> >>>>> Thanks again! >>>>> >>>>> -Colton >>>>> >>>>> On Wed, May 22, 2024 at 3:39 PM Barry Smith <[email protected] >>>>> <mailto:[email protected]>> wrote: >>>>>> >>>>>> Are you using any other command line options or did you hardwire any >>>>>> solver parameters in the code with, like, KSPSetXXX() or PCSetXXX() >>>>>> Please send all of them. >>>>>> >>>>>> Something funky definitely happened when the true residual norms >>>>>> jumped up. >>>>>> >>>>>> Could you run the same thing with -ksp_view and don't use any thing >>>>>> like -ksp_error_if_not_converged so we can see exactly what is being run. >>>>>> >>>>>> Barry >>>>>> >>>>>> >>>>>>> On May 22, 2024, at 3:21 PM, Colton Bryant >>>>>>> <[email protected] >>>>>>> <mailto:[email protected]>> wrote: >>>>>>> >>>>>>> This Message Is From an External Sender >>>>>>> This message came from outside your organization. >>>>>>> Hello, >>>>>>> >>>>>>> I am solving the Stokes equations on a MAC grid discretized by finite >>>>>>> differences using a DMSTAG object. I have tested the solver quite >>>>>>> extensively on manufactured problems and it seems to work well. As I am >>>>>>> still just trying to get things working and not yet worried about speed >>>>>>> I am using the following solver options: >>>>>>> -pc_type fieldsplit >>>>>>> -pc_fieldsplit_detect_saddle_point >>>>>>> -fieldsplit_0_pc_type lu >>>>>>> -fieldsplit_1_ksp_rtol 1.e-8 >>>>>>> >>>>>>> However I am now using this solver as an inner step of a larger code >>>>>>> and have run into issues. The code repeatedly solves the Stokes >>>>>>> equations with varying right hand sides coming from changing problem >>>>>>> geometry (the solver is a part of an overset grid scheme coupled to a >>>>>>> level set method evolving in time). After a couple timesteps I observe >>>>>>> the following output when running with >>>>>>> -fieldsplit_1_ksp_converged_reason >>>>>>> -fieldsplit_1_ksp_monitor_true_residual: >>>>>>> >>>>>>> Residual norms for back_fieldsplit_1_ solve. >>>>>>> 0 KSP preconditioned resid norm 2.826514299465e-02 true resid norm >>>>>>> 2.826514299465e-02 ||r(i)||/||b|| 1.000000000000e+00 >>>>>>> 1 KSP preconditioned resid norm 7.286621865915e-03 true resid norm >>>>>>> 7.286621865915e-03 ||r(i)||/||b|| 2.577953300039e-01 >>>>>>> 2 KSP preconditioned resid norm 1.500598474492e-03 true resid norm >>>>>>> 1.500598474492e-03 ||r(i)||/||b|| 5.309007192273e-02 >>>>>>> 3 KSP preconditioned resid norm 3.796396924978e-04 true resid norm >>>>>>> 3.796396924978e-04 ||r(i)||/||b|| 1.343137349666e-02 >>>>>>> 4 KSP preconditioned resid norm 8.091057439816e-05 true resid norm >>>>>>> 8.091057439816e-05 ||r(i)||/||b|| 2.862556697960e-03 >>>>>>> 5 KSP preconditioned resid norm 3.689113122359e-05 true resid norm >>>>>>> 3.689113122359e-05 ||r(i)||/||b|| 1.305181128239e-03 >>>>>>> 6 KSP preconditioned resid norm 2.116450533352e-05 true resid norm >>>>>>> 2.116450533352e-05 ||r(i)||/||b|| 7.487846545662e-04 >>>>>>> 7 KSP preconditioned resid norm 3.968234031201e-06 true resid norm >>>>>>> 3.968234031200e-06 ||r(i)||/||b|| 1.403932055801e-04 >>>>>>> 8 KSP preconditioned resid norm 6.666949419511e-07 true resid norm >>>>>>> 6.666949419506e-07 ||r(i)||/||b|| 2.358717739644e-05 >>>>>>> 9 KSP preconditioned resid norm 1.941522884928e-07 true resid norm >>>>>>> 1.941522884931e-07 ||r(i)||/||b|| 6.868965372998e-06 >>>>>>> 10 KSP preconditioned resid norm 6.729545258682e-08 true resid norm >>>>>>> 6.729545258626e-08 ||r(i)||/||b|| 2.380863687793e-06 >>>>>>> 11 KSP preconditioned resid norm 3.009070131709e-08 true resid norm >>>>>>> 3.009070131735e-08 ||r(i)||/||b|| 1.064586912687e-06 >>>>>>> 12 KSP preconditioned resid norm 7.849353009588e-09 true resid norm >>>>>>> 7.849353009903e-09 ||r(i)||/||b|| 2.777043445840e-07 >>>>>>> 13 KSP preconditioned resid norm 2.306283345754e-09 true resid norm >>>>>>> 2.306283346677e-09 ||r(i)||/||b|| 8.159461097060e-08 >>>>>>> 14 KSP preconditioned resid norm 9.336302495083e-10 true resid norm >>>>>>> 9.336302502503e-10 ||r(i)||/||b|| 3.303115255517e-08 >>>>>>> 15 KSP preconditioned resid norm 6.537456143401e-10 true resid norm >>>>>>> 6.537456141617e-10 ||r(i)||/||b|| 2.312903968982e-08 >>>>>>> 16 KSP preconditioned resid norm 6.389159552788e-10 true resid norm >>>>>>> 6.389159550304e-10 ||r(i)||/||b|| 2.260437724130e-08 >>>>>>> 17 KSP preconditioned resid norm 6.380905134246e-10 true resid norm >>>>>>> 6.380905136023e-10 ||r(i)||/||b|| 2.257517372981e-08 >>>>>>> 18 KSP preconditioned resid norm 6.380440605992e-10 true resid norm >>>>>>> 6.380440604688e-10 ||r(i)||/||b|| 2.257353025207e-08 >>>>>>> 19 KSP preconditioned resid norm 6.380427156582e-10 true resid norm >>>>>>> 6.380427157894e-10 ||r(i)||/||b|| 2.257348267830e-08 >>>>>>> 20 KSP preconditioned resid norm 6.380426714897e-10 true resid norm >>>>>>> 6.380426714004e-10 ||r(i)||/||b|| 2.257348110785e-08 >>>>>>> 21 KSP preconditioned resid norm 6.380426656970e-10 true resid norm >>>>>>> 6.380426658839e-10 ||r(i)||/||b|| 2.257348091268e-08 >>>>>>> 22 KSP preconditioned resid norm 6.380426650538e-10 true resid norm >>>>>>> 6.380426650287e-10 ||r(i)||/||b|| 2.257348088242e-08 >>>>>>> 23 KSP preconditioned resid norm 6.380426649918e-10 true resid norm >>>>>>> 6.380426645888e-10 ||r(i)||/||b|| 2.257348086686e-08 >>>>>>> 24 KSP preconditioned resid norm 6.380426649803e-10 true resid norm >>>>>>> 6.380426644294e-10 ||r(i)||/||b|| 2.257348086122e-08 >>>>>>> 25 KSP preconditioned resid norm 6.380426649796e-10 true resid norm >>>>>>> 6.380426649774e-10 ||r(i)||/||b|| 2.257348088061e-08 >>>>>>> 26 KSP preconditioned resid norm 6.380426649795e-10 true resid norm >>>>>>> 6.380426653788e-10 ||r(i)||/||b|| 2.257348089481e-08 >>>>>>> 27 KSP preconditioned resid norm 6.380426649795e-10 true resid norm >>>>>>> 6.380426646744e-10 ||r(i)||/||b|| 2.257348086989e-08 >>>>>>> 28 KSP preconditioned resid norm 6.380426649795e-10 true resid norm >>>>>>> 6.380426650818e-10 ||r(i)||/||b|| 2.257348088430e-08 >>>>>>> 29 KSP preconditioned resid norm 6.380426649795e-10 true resid norm >>>>>>> 6.380426649518e-10 ||r(i)||/||b|| 2.257348087970e-08 >>>>>>> 30 KSP preconditioned resid norm 6.380426652142e-10 true resid norm >>>>>>> 6.380426652142e-10 ||r(i)||/||b|| 2.257348088898e-08 >>>>>>> 31 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426646799e-10 ||r(i)||/||b|| 2.257348087008e-08 >>>>>>> 32 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426648077e-10 ||r(i)||/||b|| 2.257348087460e-08 >>>>>>> 33 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426649048e-10 ||r(i)||/||b|| 2.257348087804e-08 >>>>>>> 34 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426648142e-10 ||r(i)||/||b|| 2.257348087483e-08 >>>>>>> 35 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426651079e-10 ||r(i)||/||b|| 2.257348088522e-08 >>>>>>> 36 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426650433e-10 ||r(i)||/||b|| 2.257348088294e-08 >>>>>>> 37 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426649765e-10 ||r(i)||/||b|| 2.257348088057e-08 >>>>>>> 38 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426650364e-10 ||r(i)||/||b|| 2.257348088269e-08 >>>>>>> 39 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426650051e-10 ||r(i)||/||b|| 2.257348088159e-08 >>>>>>> 40 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426651154e-10 ||r(i)||/||b|| 2.257348088549e-08 >>>>>>> 41 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426650246e-10 ||r(i)||/||b|| 2.257348088227e-08 >>>>>>> 42 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426650702e-10 ||r(i)||/||b|| 2.257348088389e-08 >>>>>>> 43 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426651686e-10 ||r(i)||/||b|| 2.257348088737e-08 >>>>>>> 44 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426650870e-10 ||r(i)||/||b|| 2.257348088448e-08 >>>>>>> 45 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426651208e-10 ||r(i)||/||b|| 2.257348088568e-08 >>>>>>> 46 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426651441e-10 ||r(i)||/||b|| 2.257348088650e-08 >>>>>>> 47 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426650955e-10 ||r(i)||/||b|| 2.257348088478e-08 >>>>>>> 48 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426650877e-10 ||r(i)||/||b|| 2.257348088451e-08 >>>>>>> 49 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426651240e-10 ||r(i)||/||b|| 2.257348088579e-08 >>>>>>> 50 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426650534e-10 ||r(i)||/||b|| 2.257348088329e-08 >>>>>>> 51 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426648615e-10 ||r(i)||/||b|| 2.257348087651e-08 >>>>>>> 52 KSP preconditioned resid norm 6.380426652141e-10 true resid norm >>>>>>> 6.380426649523e-10 ||r(i)||/||b|| 2.257348087972e-08 >>>>>>> 53 KSP preconditioned resid norm 6.380426652140e-10 true resid norm >>>>>>> 6.380426652601e-10 ||r(i)||/||b|| 2.257348089061e-08 >>>>>>> 54 KSP preconditioned resid norm 6.380426652125e-10 true resid norm >>>>>>> 6.380427512852e-10 ||r(i)||/||b|| 2.257348393411e-08 >>>>>>> 55 KSP preconditioned resid norm 6.380426651849e-10 true resid norm >>>>>>> 6.380603444402e-10 ||r(i)||/||b|| 2.257410636701e-08 >>>>>>> 56 KSP preconditioned resid norm 6.380426646751e-10 true resid norm >>>>>>> 6.439925413105e-10 ||r(i)||/||b|| 2.278398313542e-08 >>>>>>> 57 KSP preconditioned resid norm 6.380426514019e-10 true resid norm >>>>>>> 2.674218007058e-09 ||r(i)||/||b|| 9.461186902765e-08 >>>>>>> 58 KSP preconditioned resid norm 6.380425077384e-10 true resid norm >>>>>>> 2.406759314486e-08 ||r(i)||/||b|| 8.514937691775e-07 >>>>>>> 59 KSP preconditioned resid norm 6.380406171326e-10 true resid norm >>>>>>> 3.100137288622e-07 ||r(i)||/||b|| 1.096805803957e-05 >>>>>>> Linear back_fieldsplit_1_ solve did not converge due to >>>>>>> DIVERGED_BREAKDOWN iterations 60 >>>>>>> >>>>>>> Any advice on steps I could take to elucidate the issue would be >>>>>>> greatly appreciated. Thanks so much for any help in advance! >>>>>>> >>>>>>> Best, >>>>>>> Colton Bryant >>>>>> >>>> >>
