[petsc-users] Setting up a matrix for Lagrange multiplier
Karthikeyan Chockalingam - STFC UKRI
karthikeyan.chockalingam at stfc.ac.uk
Mon Apr 24 12:58:16 CDT 2023
Changing the names to NULL produced the same error. Don’t I have to give the fields a name?
The problem solution didn’t change from one time step to the next.
[1;31m[0]PETSC ERROR: --------------------- Error Message --------------------------------------------------------------
[0;39m[0;49m[0]PETSC ERROR: No support for this operation for this object type
[0]PETSC ERROR: Unsupported viewer gmres
[0]PETSC ERROR: WARNING! There are option(s) set that were not used! Could be the program crashed before they were used or a spelling mistake, etc!
[0]PETSC ERROR: Option left: name:-fieldsplit_1_ksp_type value: preonly source: code
[0]PETSC ERROR: Option left: name:-fieldsplit_1_ksp_view value: gmres source: code
[0]PETSC ERROR: Option left: name:-fieldsplit_1_pc_type value: lu source: code
[0]PETSC ERROR: Option left: name:-options_left (no value) source: code
[0]PETSC ERROR: See https://petsc.org/release/faq/ for trouble shooting.
[0]PETSC ERROR: Petsc Development GIT revision: v3.18.4-529-g995ec06f92 GIT Date: 2023-02-03 18:41:48 +0000
[0]PETSC ERROR: /Users/karthikeyan.chockalingam/AMReX/amrFEM/build/Debug/amrFEM on a named HC20210312 by karthikeyan.chockalingam Mon Apr 24 18:51:25 2023
[0]PETSC ERROR: Configure options --with-debugging=0 --prefix=/Users/karthikeyan.chockalingam/AMReX/petsc --download-fblaslapack=yes --download-scalapack=yes --download-mumps=yes --with-hypre-dir=/Users/karthikeyan.chockalingam/AMReX/hypre/src/hypre
[0]PETSC ERROR: #1 PetscOptionsGetViewer() at /Users/karthikeyan.chockalingam/AMReX/SRC_PKG/petsc/src/sys/classes/viewer/interface/viewreg.c:309
[0]PETSC ERROR: #2 KSPSetFromOptions() at /Users/karthikeyan.chockalingam/AMReX/SRC_PKG/petsc/src/ksp/ksp/interface/itcl.c:522
[0]PETSC ERROR: #3 PCSetUp_FieldSplit() at /Users/karthikeyan.chockalingam/AMReX/SRC_PKG/petsc/src/ksp/pc/impls/fieldsplit/fieldsplit.c:1054
[0]PETSC ERROR: #4 PCSetUp() at /Users/karthikeyan.chockalingam/AMReX/SRC_PKG/petsc/src/ksp/pc/interface/precon.c:994
[0]PETSC ERROR: #5 KSPSetUp() at /Users/karthikeyan.chockalingam/AMReX/SRC_PKG/petsc/src/ksp/ksp/interface/itfunc.c:405
[0]PETSC ERROR: #6 KSPSolve_Private() at /Users/karthikeyan.chockalingam/AMReX/SRC_PKG/petsc/src/ksp/ksp/interface/itfunc.c:824
[0]PETSC ERROR: #7 KSPSolve() at /Users/karthikeyan.chockalingam/AMReX/SRC_PKG/petsc/src/ksp/ksp/interface/itfunc.c:1070
End of program
solve time 0.03416619 seconds
It will be a bit difficult for me to produce a stand-alone code.
Thank you for your help.
Best,
Karthik.
From: Matthew Knepley <knepley at gmail.com>
Date: Monday, 24 April 2023 at 18:42
To: Chockalingam, Karthikeyan (STFC,DL,HC) <karthikeyan.chockalingam at stfc.ac.uk>
Cc: petsc-users at mcs.anl.gov <petsc-users at mcs.anl.gov>
Subject: Re: [petsc-users] Setting up a matrix for Lagrange multiplier
On Mon, Apr 24, 2023 at 1:37 PM Karthikeyan Chockalingam - STFC UKRI <karthikeyan.chockalingam at stfc.ac.uk<mailto:karthikeyan.chockalingam at stfc.ac.uk>> wrote:
Great to know there is an example now.
Yes, -pc_fieldsplit_defect_saddle_point worked.
But I would like to understand what I did wrong (and why it didn’t work).
Can you show the error? Or give something self-contained that I can run.
After reading many posted posts, I needed to create PCFieldSplitSetIS to split the fields.
Yes. I would give NULL for the name here.
I set the first N indices to the field phi and the next C indices (starting from N) to the field lambda.
This looks fine. However, these are global indices, so this would not work in parallel. You would have to offset by
the first index on this process.
Thanks,
Matt
Please tell me what I did wrong and how I can fix the lines which are now commented?
PetscErrorCode ierr;
KSP ksp;
PC pc;
KSPCreate(PETSC_COMM_WORLD, &ksp);
KSPSetType(ksp, KSPGMRES);
KSPSetOperators(ksp, A[level], A[level]);
ierr = KSPGetPC(ksp,&pc);CHKERRQ(ierr);
ierr = PCSetType(pc,PCFIELDSPLIT);CHKERRQ(ierr);
……..
for (int i = 0; i < N; i++)
vec_zero_field_index[i] = i;
PetscInt * vec_first_field_index = NULL;
PetscMalloc(n * sizeof(PetscInt), &vec_first_field_index);
for (int i = 0; i < C; i++)
vec_first_field_index[i] = N + i;
IS zero_field_isx, first_field_isx;
CHKERRQ(ISCreateGeneral(PETSC_COMM_WORLD, N, vec_zero_field_index, PETSC_COPY_VALUES, &zero_field_isx));
CHKERRQ(ISCreateGeneral(PETSC_COMM_WORLD, C, vec_first_field_index, PETSC_COPY_VALUES, &first_field_isx));
ierr = PCFieldSplitSetIS(pc,"0",zero_field_isx); CHKERRQ(ierr);
ierr = PCFieldSplitSetIS(pc,"1",first_field_isx); CHKERRQ(ierr);
ierr = PetscOptionsSetValue(NULL,"-ksp_type", "fgmres"); CHKERRQ(ierr);
ierr = PetscOptionsSetValue(NULL,"-pc_type", "fieldsplit"); CHKERRQ(ierr);
/*
ierr = PetscOptionsSetValue(NULL,"-fieldsplit_0_ksp_type", "gmres"); CHKERRQ(ierr);
ierr = PetscOptionsSetValue(NULL,"-fieldsplit_0_pc_type", "jacobi"); CHKERRQ(ierr);
ierr = PetscOptionsSetValue(NULL,"-fieldsplit_1_ksp_type", "preonly"); CHKERRQ(ierr);
ierr = PetscOptionsSetValue(NULL,"-fieldsplit_1_pc_type", "lu"); CHKERRQ(ierr);*/
ierr = PetscOptionsSetValue(NULL, "-pc_fieldsplit_detect_saddle_point", NULL);CHKERRQ(ierr);
ierr = PetscOptionsSetValue(NULL, "-options_left", NULL);CHKERRQ(ierr);
ierr = KSPSetFromOptions(ksp); CHKERRQ(ierr);
KSPSolve(ksp, b, x);
Best,
Karthik.
From: Matthew Knepley <knepley at gmail.com<mailto:knepley at gmail.com>>
Date: Monday, 24 April 2023 at 17:57
To: Chockalingam, Karthikeyan (STFC,DL,HC) <karthikeyan.chockalingam at stfc.ac.uk<mailto:karthikeyan.chockalingam at stfc.ac.uk>>
Cc: petsc-users at mcs.anl.gov<mailto:petsc-users at mcs.anl.gov> <petsc-users at mcs.anl.gov<mailto:petsc-users at mcs.anl.gov>>
Subject: Re: [petsc-users] Setting up a matrix for Lagrange multiplier
On Mon, Apr 24, 2023 at 10:22 AM Karthikeyan Chockalingam - STFC UKRI <karthikeyan.chockalingam at stfc.ac.uk<mailto:karthikeyan.chockalingam at stfc.ac.uk>> wrote:
Hello,
I was able to construct the below K matrix (using submatrices P and P^T), which is of type MATAIJ
K = [A P^T
P 0]
and solved them using a direct solver.
I modified your example to create either AIJ or Nest matrices, but use the same assembly code:
https://gitlab.com/petsc/petsc/-/merge_requests/6368
However, I was reading online that this is a saddle point problem and I should be employing PCFIELDSPLIT.
Since I have one monolithic matrix K, I was not sure how to split the fields.
With this particular matrix, you can use
-pc_fieldsplit_detect_saddle_point
and it will split it automatically.
Thanks,
Matt
Best regards,
Karthik.
From: Chockalingam, Karthikeyan (STFC,DL,HC) <karthikeyan.chockalingam at stfc.ac.uk<mailto:karthikeyan.chockalingam at stfc.ac.uk>>
Date: Wednesday, 19 April 2023 at 17:52
To: Matthew Knepley <knepley at gmail.com<mailto:knepley at gmail.com>>
Cc: petsc-users at mcs.anl.gov<mailto:petsc-users at mcs.anl.gov> <petsc-users at mcs.anl.gov<mailto:petsc-users at mcs.anl.gov>>
Subject: Re: [petsc-users] Setting up a matrix for Lagrange multiplier
I have declared the mapping
ISLocalToGlobalMapping mapping;
ISLocalToGlobalMappingCreate(PETSC_COMM_WORLD, 1, n, nindices, PETSC_COPY_VALUES, &mapping);
But when I use MatSetValuesLocal(), how do I know the above mapping is employed because it is not one of the parameters passed to the function?
Thank you.
Kind regards,
Karthik.
From: Matthew Knepley <knepley at gmail.com<mailto:knepley at gmail.com>>
Date: Tuesday, 18 April 2023 at 16:21
To: Chockalingam, Karthikeyan (STFC,DL,HC) <karthikeyan.chockalingam at stfc.ac.uk<mailto:karthikeyan.chockalingam at stfc.ac.uk>>
Cc: petsc-users at mcs.anl.gov<mailto:petsc-users at mcs.anl.gov> <petsc-users at mcs.anl.gov<mailto:petsc-users at mcs.anl.gov>>
Subject: Re: [petsc-users] Setting up a matrix for Lagrange multiplier
On Tue, Apr 18, 2023 at 11:16 AM Karthikeyan Chockalingam - STFC UKRI <karthikeyan.chockalingam at stfc.ac.uk<mailto:karthikeyan.chockalingam at stfc.ac.uk>> wrote:
Thank you for your response. I spend some time understanding how
MatSetValuesLocal and ISLocalToGlobalMappingCreate work.
You can look at SNES ex28 where we do this with DMCOMPOSITE.
Q1) Will the matrix K be of type MATMPIAIJ or MATIS?
K = [A P^T
P 0]
I assume MPIAIJ since IS is only used for Neumann-Neumann decompositions.
Q2) Can I use both MatSetValues() to MatSetValuesLocal() to populate K? Since I have already used MatSetValues() to construct A.
You can, and there would be no changes in serial if K is exactly the upper left block, but in parallel global indices would change.
Q3) What are the advantages of using MatSetValuesLocal()? Is it that I can construct P directly using local indies and map the entrees to the global index in K?
You have a monolithic K, so that you can use sparse direct solvers to check things. THis is impossible with separate storage.
Q4) I probably don’t have to construct an independent P matrix
You wouldn't in this case.
Thanks,
Matt
Best regards,
Karthik.
From: Matthew Knepley <knepley at gmail.com<mailto:knepley at gmail.com>>
Date: Tuesday, 18 April 2023 at 11:08
To: Chockalingam, Karthikeyan (STFC,DL,HC) <karthikeyan.chockalingam at stfc.ac.uk<mailto:karthikeyan.chockalingam at stfc.ac.uk>>
Cc: petsc-users at mcs.anl.gov<mailto:petsc-users at mcs.anl.gov> <petsc-users at mcs.anl.gov<mailto:petsc-users at mcs.anl.gov>>
Subject: Re: [petsc-users] Setting up a matrix for Lagrange multiplier
On Tue, Apr 18, 2023 at 5:24 AM Karthikeyan Chockalingam - STFC UKRI via petsc-users <petsc-users at mcs.anl.gov<mailto:petsc-users at mcs.anl.gov>> wrote:
Hello,
I'm solving a problem using the Lagrange multiplier, the matrix has the form
K = [A P^T
P 0]
I am familiar with constructing K using MATMPIAIJ. However, I would like to know if had [A], can I augment it with [P], [P^T] and [0] of type MATMPIAIJ? Likewise for vectors as well.
Can you please point me to the right resource, if it is a common operation in PETSc?
You can do this at least 2 ways:
1) Assemble you submatrices directly into the larger matrix by constructing local-to-global maps for the emplacement. so that you do
not change your assembly code, except to change MatSetValues() to MatSetValuesLocal(). This is usually preferable.
2) Use MATNEST and VecNEST to put pointers to submatrices and subvectors directly in.
Thanks,
Matt
Many thanks.
Kind regards,
Karthik.
--
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/>
--
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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