[petsc-users] Diagnosing Convergence Issue in Fieldsplit Problem
Colton Bryant
coltonbryant2021 at u.northwestern.edu
Wed May 22 17:00:11 CDT 2024
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
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20240522/9c5c4149/attachment-0001.html>
More information about the petsc-users
mailing list