Preconditioner for the Schur complement formed from A11
But
PC Object: (fieldsplit_pressure_) 1 MPI process
>
> type: ilu
> out-of-place factorization
> 0 levels of fill
> tolerance for zero pivot 2.22045e-14
> matrix ordering: natural
> factor fill ratio given 1., needed 1.
> Factored matrix follows:
> Mat Object: (fieldsplit_pressure_) 1 MPI process
> type: seqaij
> rows=25, cols=25
> package used to perform factorization: petsc
> total: nonzeros=105, allocated nonzeros=105
> not using I-node routines
So it is trying to do ILU on A11 (to use as the preconditioner of the
Schur complement). But A11 is identically zero so ILU will produce a zero pivot
So you need to set a different preconditioner for S. This can be done
with
-pc_fieldsplit_schur_precondition <self,selfp,user,a11,full> See
PCFieldSplitSetSchurPre
First use
-pc_fieldsplit_schur_precondition full -fieldsplit_pressure_pc_type
svd (note the full S is singular so LU should fail).
and that should make the PCFIELDSPLIT a direct solver. You then explore
cheaper options (since computing S explicitly to produce a preconditioner
is not reasonable except for small problems). So try next
-pc_fieldsplit_schur_precondition self -fieldsplit_pressure_pc_type
jacobi
For more advanced tuning Matt can help you out once you have the basics
working.
> On May 30, 2024, at 4:49 PM, Colton Bryant
> <[email protected]> wrote:
>
> Hi Barry,
>
> Yes, each index set has the correct entries when I checked manually on a
> small example.
>
> For the nullspace I was trying to manually build the constant basis on a
> compatible DMStag containing just the pressure nodes and creating the
> nullspace from that but that does not seem to work. Using
> MatNullSpaceCreate(comm,PETSC_TRUE,0,NULL,&sp) does show that the Schur
> system has the attached null space. However the system still fails to
> converge with the schur block giving the error
>
> Linear fieldsplit_pressure_ solve did not converge due to DIVERGED_PC_FAILED
> iterations 0
> PC failed due to FACTOR_NUMERIC_ZEROPIVOT
>
> The output from -ksp_view is
>
> KSP Object: 1 MPI process
> type: fgmres
> 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-12, absolute=1e-50, divergence=10000.
> right preconditioning
> using UNPRECONDITIONED norm type for convergence test
> PC Object: 1 MPI process
> type: fieldsplit
> FieldSplit with Schur preconditioner, factorization FULL
> Preconditioner for the Schur complement formed from A11
> Split info:
> Split number 0 Defined by IS
> Split number 1 Defined by IS
> KSP solver for A00 block
> KSP Object: (fieldsplit_velocity_) 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: (fieldsplit_velocity_) 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 2.17695
> Factored matrix follows:
> Mat Object: (fieldsplit_velocity_) 1 MPI process
> type: seqaij
> rows=60, cols=60
> package used to perform factorization: petsc
> total: nonzeros=1058, allocated nonzeros=1058
> using I-node routines: found 35 nodes, limit used is 5
> linear system matrix = precond matrix:
> Mat Object: (fieldsplit_velocity_) 1 MPI process
> type: seqaij
> rows=60, cols=60
> total: nonzeros=486, allocated nonzeros=486
> total number of mallocs used during MatSetValues calls=0
> using I-node routines: found 35 nodes, limit used is 5
> KSP solver for S = A11 - A10 inv(A00) A01
> KSP Object: (fieldsplit_pressure_) 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-12, absolute=1e-50, divergence=10000.
> left preconditioning
> using PRECONDITIONED norm type for convergence test
> PC Object: (fieldsplit_pressure_) 1 MPI process
> type: ilu
> out-of-place factorization
> 0 levels of fill
> tolerance for zero pivot 2.22045e-14
> matrix ordering: natural
> factor fill ratio given 1., needed 1.
> Factored matrix follows:
> Mat Object: (fieldsplit_pressure_) 1 MPI process
> type: seqaij
> rows=25, cols=25
> package used to perform factorization: petsc
> total: nonzeros=105, allocated nonzeros=105
> not using I-node routines
> linear system matrix followed by preconditioner matrix:
> Mat Object: (fieldsplit_pressure_) 1 MPI process
> type: schurcomplement
> rows=25, cols=25
> has attached null space
> Schur complement A11 - A10 inv(A00) A01
> A11
> Mat Object: (fieldsplit_pressure_) 1 MPI process
> type: seqaij
> rows=25, cols=25
> total: nonzeros=105, allocated nonzeros=105
> total number of mallocs used during MatSetValues calls=0
> has attached null space
> not using I-node routines
> A10
> Mat Object: 1 MPI process
> type: seqaij
> rows=25, cols=60
> total: nonzeros=220, allocated nonzeros=220
> total number of mallocs used during MatSetValues calls=0
> not using I-node routines
> KSP solver for A00 block viewable with the additional option
> -fieldsplit_velocity_ksp_view
> A01
> Mat Object: 1 MPI process
> type: seqaij
> rows=60, cols=25
> total: nonzeros=220, allocated nonzeros=220
> total number of mallocs used during MatSetValues calls=0
> using I-node routines: found 35 nodes, limit used is 5
> Mat Object: (fieldsplit_pressure_) 1 MPI process
> type: seqaij
> rows=25, cols=25
> total: nonzeros=105, allocated nonzeros=105
> total number of mallocs used during MatSetValues calls=0
> has attached null space
> not using I-node routines
> linear system matrix = precond matrix:
> Mat Object: 1 MPI process
> type: seqaij
> rows=85, cols=85
> total: nonzeros=1031, allocated nonzeros=1031
> total number of mallocs used during MatSetValues calls=0
> has attached null space
> using I-node routines: found 35 nodes, limit used is 5
>
>
> On Thu, May 30, 2024 at 1:53 PM Barry Smith <[email protected]
> <mailto:[email protected]>> wrote:
>>
>>
>>> On May 30, 2024, at 3:15 PM, Colton Bryant
>>> <[email protected]
>>> <mailto:[email protected]>> wrote:
>>>
>>> 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.
>>
>> First confirm that each IS has the entries you expect
>>
>> Then for the pressure IS are you using
>> PetscObjectCompose((PetscObject*)is,"nullspace", (PetscObject *)sp); where
>> sp is the null space of the pressure variables
>> which I think you can create using
>> MatNullSpaceCreate(comm,PETSC_TRUE,0,NULL,&sp);
>>
>> PCFIELDSPLIT is suppose to snag this null space that you provided and use
>> it on the Shur system. If you run with -ksp_view it should list what
>> matrices have an attached null space.
>>
>>
>>
>>>
>>> Thanks,
>>> Colton
>>>
>>> On Thu, May 23, 2024 at 12:55 PM Barry Smith <[email protected]
>>> <mailto:[email protected]>> 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
>>>>> <[email protected]
>>>>> <mailto:[email protected]>> 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 <[email protected]
>>>>> <mailto:[email protected]>> 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
>>>>>>> <[email protected]
>>>>>>> <mailto:[email protected]>> 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 <[email protected]
>>>>>>> <mailto:[email protected]>> wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>> Sorry I gave the wrong option. Use -fieldsplit_0_ksp_type preonly
>>>>>>>>
>>>>>>>> Barry
>>>>>>>>
>>>>>>>>> On May 23, 2024, at 12:51 PM, Colton Bryant
>>>>>>>>> <[email protected]
>>>>>>>>> <mailto:[email protected]>> 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 <[email protected]
>>>>>>>>> <mailto:[email protected]>> wrote:
>>>>>>>>>>
>>>>>>>>>> Use -pc_fieldsplit_0_ksp_type preonly
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>> On May 23, 2024, at 12:43 PM, Colton Bryant
>>>>>>>>>>> <[email protected]
>>>>>>>>>>> <mailto:[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!ZsCPHC5g2pfiwFqZ9iGAXJb3Jd0OvtH31f70si-azCrYjFOFCmjN6rD5qICGN9V_Ll2kn3o1fkako4PHyz78-ho$
>>>>>>>>>>> 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
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>
>>>>>>
>>>>
>>
