[petsc-users] Diagnosing Convergence Issue in Fieldsplit Problem
Colton Bryant
coltonbryant2021 at u.northwestern.edu
Thu May 30 14:15:07 CDT 2024
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 <bsmith at 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 <
> coltonbryant2021 at 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 <bsmith at 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 <
>> coltonbryant2021 at 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 <bsmith at 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 <
>>> coltonbryant2021 at 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 <bsmith at petsc.dev> wrote:
>>>
>>>>
>>>> Use -pc_fieldsplit_0_ksp_type preonly
>>>>
>>>>
>>>>
>>>> On May 23, 2024, at 12:43 PM, Colton Bryant <
>>>> coltonbryant2021 at 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 <bsmith at 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 <
>>>>> coltonbryant2021 at 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 <bsmith at 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 <
>>>>>> coltonbryant2021 at 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 <bsmith at 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 <
>>>>>>> coltonbryant2021 at 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
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
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