Hi Barry, Do you know of an example that demonstrates this approach? I have tried implementing this using DMStagCreateISFromStencils and then calling PCFieldSplitSetIS with fields named "velocity" and "pressure" respectively, but when I look at -ksp_view the fields are being set to "fieldsplit_face" and "fieldsplit_element" and as problems are not converging I expect the constant null space is not being attached.
Thanks, Colton On Thu, May 23, 2024 at 12:55 PM Barry Smith <bsm...@petsc.dev> wrote: > > Unfortunately it cannot automatically because > -pc_fieldsplit_detect_saddle_point just grabs part of the matrix (having no > concept of "what part" so doesn't know to grab the null space information. > > It would be possible for PCFIELDSPLIT to access the null space of the > larger matrix directly as vectors and check if they are all zero in the 00 > block, then it would know that the null space only applied to the second > block and could use it for the Schur complement. > > Matt, Jed, Stefano, Pierre does this make sense? > > Colton, > > Meanwhile the quickest thing you can do is to generate the IS the > defines the first and second block (instead of using > -pc_fieldsplit_detect_saddle_point) and use PetscObjectCompose to attach > the constant null space to the second block with the name "nullspace". > PCFIELDSPLIT will then use this null space for the Schur complement solve. > > Barry > > > On May 23, 2024, at 2:43 PM, Colton Bryant < > coltonbryant2...@u.northwestern.edu> wrote: > > Yes, the original operator definitely has a constant null space > corresponding to the constant pressure mode. I am currently handling this > by using the MatSetNullSpace function when the matrix is being created. > Does this information get passed to the submatrices of the fieldsplit? > > -Colton > > On Thu, May 23, 2024 at 12:36 PM Barry Smith <bsm...@petsc.dev> wrote: > >> >> Ok, >> >> So what is happening is that GMRES with a restart of 30 is running on >> the Schur complement system with no preconditioning and LU (as a direct >> solver) is being used in the application of S (the Schur complement). The >> convergence of GMRES is stagnating after getting about 8 digits of accuracy >> in the residual. Then at the second GMRES >> restart it is comparing the explicitly computing residual b - Ax with >> that computed inside the GMRES algorithm (via a recursive formula) and >> finding a large difference so generating an error. Since you are using a >> direct solver on the A_{00} block and it is well-conditioned this problem >> is not expected. >> >> Is it possible that the S operator has a null space (perhaps of the >> constant vector)? Or, relatedly, does your original full matrix have a null >> space? >> >> We have a way to associated null spaces of the submatrices in >> PCFIELDSPLIT by attaching them to the IS that define the fields, but >> unfortunately not trivially when using -pc_fieldsplit_detect_saddle_point. >> And sadly the current support seems completely undocumented. >> >> Barry >> >> >> >> On May 23, 2024, at 2:16 PM, Colton Bryant < >> coltonbryant2...@u.northwestern.edu> wrote: >> >> Hi Barry, >> >> I saw that was reporting as an unused option and the error message I sent >> was run with -fieldsplit_0_ksp_type preonly. >> >> -Colton >> >> On Thu, May 23, 2024 at 12:13 PM Barry Smith <bsm...@petsc.dev> wrote: >> >>> >>> >>> Sorry I gave the wrong option. Use -fieldsplit_0_ksp_type preonly >>> >>> Barry >>> >>> On May 23, 2024, at 12:51 PM, Colton Bryant < >>> coltonbryant2...@u.northwestern.edu> wrote: >>> >>> That produces the error: >>> >>> [0]PETSC ERROR: Residual norm computed by GMRES recursion formula >>> 2.68054e-07 is far from the computed residual norm 6.86309e-06 at restart, >>> residual norm at start of cycle 2.68804e-07 >>> >>> The rest of the error is identical. >>> >>> On Thu, May 23, 2024 at 10:46 AM Barry Smith <bsm...@petsc.dev> wrote: >>> >>>> >>>> Use -pc_fieldsplit_0_ksp_type preonly >>>> >>>> >>>> >>>> On May 23, 2024, at 12:43 PM, Colton Bryant < >>>> coltonbryant2...@u.northwestern.edu> 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!eHxid0vR_Oq4B4_2xQfLg8TwCHSypxeshF2stG1z1p0_AqRPJ0nwTZlAyhArCS__aZuybvfmGtTLuAtMLsCePBg6n627v_VOQ313YZE5bEg$ >>>> 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 <bsm...@petsc.dev> 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 < >>>>> coltonbryant2...@u.northwestern.edu> 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 <bsm...@petsc.dev> 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 < >>>>>> coltonbryant2...@u.northwestern.edu> 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 <bsm...@petsc.dev> 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 < >>>>>>> coltonbryant2...@u.northwestern.edu> 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 >>>>>>> >>>>>>> >>>>>>> >>>>>> >>>>> >>>> >>> >> >