[petsc-users] Question regarding naming of fieldsplit splits
Blauth, Sebastian
sebastian.blauth at itwm.fraunhofer.de
Thu Aug 1 08:19:52 CDT 2024
Hello everyone,
I have a follow up on my question. I noticed the following behavior. Let’s assume I have 5 fields which I want to group with the following options:
-ksp_type fgmres
-ksp_max_it 1
-ksp_monitor_true_residual
-ksp_view
-pc_type fieldsplit
-pc_fieldsplit_type multiplicative
-pc_fieldsplit_0_fields 0,1
-pc_fieldsplit_1_fields 2
-pc_fieldsplit_2_fields 3,4
-fieldsplit_0_ksp_type preonly
-fieldsplit_0_pc_type jacobi
-fieldsplit_2_ksp_type preonly
-fieldsplit_2_pc_type jacobi
Then, the first split is fine, but both the second and third splits get the same prefix, i.e., “fieldsplit_2”. This is shown in the output of the ksp_view, which I attach below.
The first one gets the prefix as there is only a single split (and I choose as name the index) and the third split gets the name as it groups two other fields, so the “outer” name is taken. Is there any way to circumvent this, other than using custom names for the splits which are unique?
Thanks for your time and best regards,
Sebastian Blauth
The output of “ksp_view” is the following
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=1, initial guess is zero
tolerances: relative=1e-05, absolute=1e-50, divergence=10000.
right preconditioning
using UNPRECONDITIONED norm type for convergence test
PC Object: 1 MPI process
type: fieldsplit
FieldSplit with MULTIPLICATIVE composition: total splits = 3
Solver info for each split is in the following KSP objects:
Split number 0 Defined by IS
KSP Object: (fieldsplit_0_) 1 MPI process
type: preonly
maximum iterations=10000, initial guess is zero
tolerances: relative=1e-05, absolute=1e-50, divergence=10000.
left preconditioning
using NONE norm type for convergence test
PC Object: (fieldsplit_0_) 1 MPI process
type: jacobi
type DIAGONAL
linear system matrix = precond matrix:
Mat Object: (fieldsplit_0_) 1 MPI process
type: seqaij
rows=243, cols=243
total: nonzeros=4473, allocated nonzeros=4473
total number of mallocs used during MatSetValues calls=0
using I-node routines: found 86 nodes, limit used is 5
Split number 1 Defined by IS
KSP Object: (fieldsplit_2_) 1 MPI process
type: preonly
maximum iterations=10000, initial guess is zero
tolerances: relative=1e-05, absolute=1e-50, divergence=10000.
left preconditioning
using NONE norm type for convergence test
PC Object: (fieldsplit_2_) 1 MPI process
type: jacobi
type DIAGONAL
linear system matrix = precond matrix:
Mat Object: (fieldsplit_2_) 1 MPI process
type: seqaij
rows=81, cols=81
total: nonzeros=497, allocated nonzeros=497
total number of mallocs used during MatSetValues calls=0
not using I-node routines
Split number 2 Defined by IS
KSP Object: (fieldsplit_2_) 1 MPI process
type: preonly
maximum iterations=10000, initial guess is zero
tolerances: relative=1e-05, absolute=1e-50, divergence=10000.
left preconditioning
using NONE norm type for convergence test
PC Object: (fieldsplit_2_) 1 MPI process
type: jacobi
type DIAGONAL
linear system matrix = precond matrix:
Mat Object: (fieldsplit_2_) 1 MPI process
type: seqaij
rows=243, cols=243
total: nonzeros=4473, allocated nonzeros=4473
total number of mallocs used during MatSetValues calls=0
using I-node routines: found 85 nodes, limit used is 5
linear system matrix = precond matrix:
Mat Object: 1 MPI process
type: seqaij
rows=567, cols=567
total: nonzeros=24353, allocated nonzeros=24353
total number of mallocs used during MatSetValues calls=0
using I-node routines: found 173 nodes, limit used is 5
--
Dr. Sebastian Blauth
Fraunhofer-Institut für
Techno- und Wirtschaftsmathematik ITWM
Abteilung Transportvorgänge
Fraunhofer-Platz 1, 67663 Kaiserslautern
Telefon: +49 631 31600-4968
sebastian.blauth at itwm.fraunhofer.de <mailto:sebastian.blauth at itwm.fraunhofer.de>
https://www.itwm.fraunhofer.de
From: petsc-users <petsc-users-bounces at mcs.anl.gov> On Behalf Of Blauth, Sebastian
Sent: Tuesday, July 2, 2024 11:47 AM
To: Matthew Knepley <knepley at gmail.com>
Cc: petsc-users at mcs.anl.gov
Subject: Re: [petsc-users] Question regarding naming of fieldsplit splits
Hi Matt,
thanks fort he answer and clarification. Then I’ll work around this issue in python, where I set the options.
Best,
Sebastian
--
Dr. Sebastian Blauth
Fraunhofer-Institut für
Techno- und Wirtschaftsmathematik ITWM
Abteilung Transportvorgänge
Fraunhofer-Platz 1, 67663 Kaiserslautern
Telefon: +49 631 31600-4968
sebastian.blauth at itwm.fraunhofer.de <mailto:sebastian.blauth at itwm.fraunhofer.de>
https://www.itwm.fraunhofer.de
From: Matthew Knepley <knepley at gmail.com <mailto:knepley at gmail.com> >
Sent: Monday, July 1, 2024 4:30 PM
To: Blauth, Sebastian <sebastian.blauth at itwm.fraunhofer.de <mailto:sebastian.blauth at itwm.fraunhofer.de> >
Cc: petsc-users at mcs.anl.gov <mailto:petsc-users at mcs.anl.gov>
Subject: Re: [petsc-users] Question regarding naming of fieldsplit splits
On Mon, Jul 1, 2024 at 9:48 AM Blauth, Sebastian <sebastian.blauth at itwm.fraunhofer.de <mailto:sebastian.blauth at itwm.fraunhofer.de> > wrote:
Dear Matt,
thanks a lot for your help. Unfortunately, for me these extra options do not have any effect, I still get the “u” and “p” fieldnames. Also, this would not help me to get rid of the “c” fieldname – on that level of the fieldsplit I am basically using your approach already, and still it does show up. The output of the -ksp_view is unchanged, so that I do not attach it here again. Maybe I misunderstood you?
Oh, we make an exception for single fields, since we think you would want to use the name. I have to make an extra option to shut off naming.
Thanks,
Matt
Thanks for the help and best regards,
Sebastian
--
Dr. Sebastian Blauth
Fraunhofer-Institut für
Techno- und Wirtschaftsmathematik ITWM
Abteilung Transportvorgänge
Fraunhofer-Platz 1, 67663 Kaiserslautern
Telefon: +49 631 31600-4968
sebastian.blauth at itwm.fraunhofer.de <mailto:sebastian.blauth at itwm.fraunhofer.de>
https://www.itwm.fraunhofer.de
From: Matthew Knepley <knepley at gmail.com <mailto:knepley at gmail.com> >
Sent: Monday, July 1, 2024 2:27 PM
To: Blauth, Sebastian <sebastian.blauth at itwm.fraunhofer.de <mailto:sebastian.blauth at itwm.fraunhofer.de> >
Cc: petsc-users at mcs.anl.gov <mailto:petsc-users at mcs.anl.gov>
Subject: Re: [petsc-users] Question regarding naming of fieldsplit splits
On Fri, Jun 28, 2024 at 4:05 AM Blauth, Sebastian <sebastian.blauth at itwm.fraunhofer.de <mailto:sebastian.blauth at itwm.fraunhofer.de> > wrote:
Hello everyone,
I have a question regarding the naming convention using PETSc’s PCFieldsplit. I have been following https://lists.mcs.anl.gov/pipermail/petsc-users/2019-January/037262.html to create a DMShell with FEniCS in order to customize PCFieldsplit for my application.
I am using the following options, which work nicely for me:
-ksp_type fgmres
-pc_type fieldsplit
-pc_fieldsplit_0_fields 0, 1
-pc_fieldsplit_1_fields 2
-pc_fieldsplit_type additive
-fieldsplit_0_ksp_type fgmres
-fieldsplit_0_pc_type fieldsplit
-fieldsplit_0_pc_fieldsplit_type schur
-fieldsplit_0_pc_fieldsplit_schur_fact_type full
-fieldsplit_0_pc_fieldsplit_schur_precondition selfp
-fieldsplit_0_fieldsplit_u_ksp_type preonly
-fieldsplit_0_fieldsplit_u_pc_type lu
-fieldsplit_0_fieldsplit_p_ksp_type cg
-fieldsplit_0_fieldsplit_p_ksp_rtol 1e-14
-fieldsplit_0_fieldsplit_p_ksp_atol 1e-30
-fieldsplit_0_fieldsplit_p_pc_type icc
-fieldsplit_0_ksp_rtol 1e-14
-fieldsplit_0_ksp_atol 1e-30
-fieldsplit_0_ksp_monitor_true_residual
-fieldsplit_c_ksp_type preonly
-fieldsplit_c_pc_type lu
-ksp_view
By default, we use the field names, but you can prevent this by specifying the fields by hand, so
-fieldsplit_0_pc_fieldsplit_0_fields 0
-fieldsplit_0_pc_fieldsplit_1_fields 1
should remove the 'u' and 'p' fieldnames. It is somewhat hacky, but I think easier to remember than
some extra option.
Thanks,
Matt
Note that this is just an academic example (sorry for the low solver tolerances) to test the approach, consisting of a Stokes equation and some concentration equation (which is not even coupled to Stokes, just for testing).
Completely analogous to https://lists.mcs.anl.gov/pipermail/petsc-users/2019-January/037262.html, I translate my IS’s to a PETSc Section, which is then supplied to a DMShell and assigned to a KSP. I am not so familiar with the code or how / why this works, but it seems to do so perfectly. I name my sections with petsc4py using
section.setFieldName(0, "u")
section.setFieldName(1, "p")
section.setFieldName(2, "c")
However, this is also reflected in the way I can access the fieldsplit options from the command line. My question is: Is there any way of not using the FieldNames specified in python but use the index of the field as defined with “-pc_fieldsplit_0_fields 0, 1” and “-pc_fieldsplit_1_fields 2”, i.e., instead of the prefix “fieldsplit_0_fieldsplit_u” I want to write “fieldsplit_0_fieldsplit_0”, instead of “fieldsplit_0_fieldsplit_p” I want to use “fieldsplit_0_fieldsplit_1”, and instead of “fieldsplit_c” I want to use “fieldsplit_1”. Just changing the names of the fields to
section.setFieldName(0, "0")
section.setFieldName(1, "1")
section.setFieldName(2, "2")
does obviously not work as expected, as it works for velocity and pressure, but not for the concentration – the prefix there is then “fieldsplit_2” and not “fieldsplit_1”. In the docs, I have found https://petsc.org/main/manualpages/PC/PCFieldSplitSetFields/ which seems to suggest that the fieldname can potentially be supplied, but I don’t see how to do so from the command line. Also, for the sake of completeness, I attach the output of the solve with “-ksp_view” below.
Thanks a lot in advance and best regards,
Sebastian
The output of ksp_view is the following:
KSP Object: 1 MPI processes
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-05, absolute=1e-11, divergence=10000.
right preconditioning
using UNPRECONDITIONED norm type for convergence test
PC Object: 1 MPI processes
type: fieldsplit
FieldSplit with ADDITIVE composition: total splits = 2
Solver info for each split is in the following KSP objects:
Split number 0 Defined by IS
KSP Object: (fieldsplit_0_) 1 MPI processes
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-14, absolute=1e-30, divergence=10000.
right preconditioning
using UNPRECONDITIONED norm type for convergence test
PC Object: (fieldsplit_0_) 1 MPI processes
type: fieldsplit
FieldSplit with Schur preconditioner, factorization FULL
Preconditioner for the Schur complement formed from Sp, an assembled approximation to S, which uses A00's diagonal's inverse
Split info:
Split number 0 Defined by IS
Split number 1 Defined by IS
KSP solver for A00 block
KSP Object: (fieldsplit_0_fieldsplit_u_) 1 MPI processes
type: preonly
maximum iterations=10000, initial guess is zero
tolerances: relative=1e-05, absolute=1e-50, divergence=10000.
left preconditioning
using NONE norm type for convergence test
PC Object: (fieldsplit_0_fieldsplit_u_) 1 MPI processes
type: lu
out-of-place factorization
tolerance for zero pivot 2.22045e-14
matrix ordering: nd
factor fill ratio given 5., needed 3.92639
Factored matrix follows:
Mat Object: 1 MPI processes
type: seqaij
rows=4290, cols=4290
package used to perform factorization: petsc
total: nonzeros=375944, allocated nonzeros=375944
using I-node routines: found 2548 nodes, limit used is 5
linear system matrix = precond matrix:
Mat Object: (fieldsplit_0_fieldsplit_u_) 1 MPI processes
type: seqaij
rows=4290, cols=4290
total: nonzeros=95748, allocated nonzeros=95748
total number of mallocs used during MatSetValues calls=0
using I-node routines: found 3287 nodes, limit used is 5
KSP solver for S = A11 - A10 inv(A00) A01
KSP Object: (fieldsplit_0_fieldsplit_p_) 1 MPI processes
type: cg
maximum iterations=10000, initial guess is zero
tolerances: relative=1e-14, absolute=1e-30, divergence=10000.
left preconditioning
using PRECONDITIONED norm type for convergence test
PC Object: (fieldsplit_0_fieldsplit_p_) 1 MPI processes
type: icc
out-of-place factorization
0 levels of fill
tolerance for zero pivot 2.22045e-14
using Manteuffel shift [POSITIVE_DEFINITE]
matrix ordering: natural
factor fill ratio given 1., needed 1.
Factored matrix follows:
Mat Object: 1 MPI processes
type: seqsbaij
rows=561, cols=561
package used to perform factorization: petsc
total: nonzeros=5120, allocated nonzeros=5120
block size is 1
linear system matrix followed by preconditioner matrix:
Mat Object: (fieldsplit_0_fieldsplit_p_) 1 MPI processes
type: schurcomplement
rows=561, cols=561
Schur complement A11 - A10 inv(A00) A01
A11
Mat Object: (fieldsplit_0_fieldsplit_p_) 1 MPI processes
type: seqaij
rows=561, cols=561
total: nonzeros=3729, allocated nonzeros=3729
total number of mallocs used during MatSetValues calls=0
not using I-node routines
A10
Mat Object: 1 MPI processes
type: seqaij
rows=561, cols=4290
total: nonzeros=19938, allocated nonzeros=19938
total number of mallocs used during MatSetValues calls=0
not using I-node routines
KSP of A00
KSP Object: (fieldsplit_0_fieldsplit_u_) 1 MPI processes
type: preonly
maximum iterations=10000, initial guess is zero
tolerances: relative=1e-05, absolute=1e-50, divergence=10000.
left preconditioning
using NONE norm type for convergence test
PC Object: (fieldsplit_0_fieldsplit_u_) 1 MPI processes
type: lu
out-of-place factorization
tolerance for zero pivot 2.22045e-14
matrix ordering: nd
factor fill ratio given 5., needed 3.92639
Factored matrix follows:
Mat Object: 1 MPI processes
type: seqaij
rows=4290, cols=4290
package used to perform factorization: petsc
total: nonzeros=375944, allocated nonzeros=375944
using I-node routines: found 2548 nodes, limit used is 5
linear system matrix = precond matrix:
Mat Object: (fieldsplit_0_fieldsplit_u_) 1 MPI processes
type: seqaij
rows=4290, cols=4290
total: nonzeros=95748, allocated nonzeros=95748
total number of mallocs used during MatSetValues calls=0
using I-node routines: found 3287 nodes, limit used is 5
A01
Mat Object: 1 MPI processes
type: seqaij
rows=4290, cols=561
total: nonzeros=19938, allocated nonzeros=19938
total number of mallocs used during MatSetValues calls=0
using I-node routines: found 3287 nodes, limit used is 5
Mat Object: 1 MPI processes
type: seqaij
rows=561, cols=561
total: nonzeros=9679, allocated nonzeros=9679
total number of mallocs used during MatSetValues calls=0
not using I-node routines
linear system matrix = precond matrix:
Mat Object: (fieldsplit_0_) 1 MPI processes
type: seqaij
rows=4851, cols=4851
total: nonzeros=139353, allocated nonzeros=139353
total number of mallocs used during MatSetValues calls=0
using I-node routines: found 3830 nodes, limit used is 5
Split number 1 Defined by IS
KSP Object: (fieldsplit_c_) 1 MPI processes
type: preonly
maximum iterations=10000, initial guess is zero
tolerances: relative=1e-05, absolute=1e-50, divergence=10000.
left preconditioning
using NONE norm type for convergence test
PC Object: (fieldsplit_c_) 1 MPI processes
type: lu
out-of-place factorization
tolerance for zero pivot 2.22045e-14
matrix ordering: nd
factor fill ratio given 5., needed 4.24323
Factored matrix follows:
Mat Object: 1 MPI processes
type: seqaij
rows=561, cols=561
package used to perform factorization: petsc
total: nonzeros=15823, allocated nonzeros=15823
not using I-node routines
linear system matrix = precond matrix:
Mat Object: (fieldsplit_c_) 1 MPI processes
type: seqaij
rows=561, cols=561
total: nonzeros=3729, allocated nonzeros=3729
total number of mallocs used during MatSetValues calls=0
not using I-node routines
linear system matrix = precond matrix:
Mat Object: 1 MPI processes
type: seqaij
rows=5412, cols=5412
total: nonzeros=190416, allocated nonzeros=190416
total number of mallocs used during MatSetValues calls=0
using I-node routines: found 3833 nodes, limit used is 5
--
Dr. Sebastian Blauth
Fraunhofer-Institut für
Techno- und Wirtschaftsmathematik ITWM
Abteilung Transportvorgänge
Fraunhofer-Platz 1, 67663 Kaiserslautern
Telefon: +49 631 31600-4968
sebastian.blauth at itwm.fraunhofer.de <mailto:sebastian.blauth at itwm.fraunhofer.de>
https://www.itwm.fraunhofer.de
--
What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
-- Norbert Wiener
https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
--
What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
-- Norbert Wiener
https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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