Ah thanks for that! Sorry I had incorrectly assumed the preconditioner on S
would be as it was previously. I'll take a look.
Thanks again for all the help.
Best,
Colton
On Thu, May 30, 2024 at 3:25 PM Barry Smith <bsm...@petsc.dev> wrote:
>
> 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 <
> coltonbryant2...@u.northwestern.edu> 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 <bsm...@petsc.dev> wrote:
>
>>
>>
>> On May 30, 2024, at 3:15 PM, Colton Bryant <
>> coltonbryant2...@u.northwestern.edu> 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 <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!csOPLvnC21pdtnvyvDYTttQSWUK793-ZufEaNlRAiw7pC_uVTB8bNOe1Yblvqz1RP_6witFXQtpRRrne-a7JoKY-yVhALTcZH2_f3KlmH5Y$
>>>>>> 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
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>
