[petsc-users] Setting up a PETSc section for field-split
Luc Berger-Vergiat
lb2653 at columbia.edu
Mon Jan 27 13:35:10 CST 2014
Thanks Matt,
this indeed setting the number of fields earlier solve my issue!
I have now made some progress getting my DM setup but I am having
troubles setting my splitfield options.
I ran my problem with the -ksp_view option to see what is going on and I
guess that somehow the section that I define in my DM is not used by the
preconditioner to split the fields.
Here is the output of PETSc
KSP Object: 1 MPI processes
type: gmres
GMRES: restart=30, using Classical (unmodified) Gram-Schmidt
Orthogonalization with no iterative refinement
GMRES: happy breakdown tolerance 1e-30
maximum iterations=10000, initial guess is zero
tolerances: relative=1e-08, absolute=1e-16, divergence=1e+16
left preconditioning
using PRECONDITIONED norm type for convergence test
PC Object: 1 MPI processes
type: fieldsplit
FieldSplit with MULTIPLICATIVE composition: total splits = 4
Solver info for each split is in the following KSP objects:
Split number 0 Defined by IS
KSP Object: (fieldsplit_Field_0_) 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_Field_0_) 1 MPI processes
type: ilu
ILU: out-of-place factorization
0 levels of fill
tolerance for zero pivot 2.22045e-14
using diagonal shift on blocks to prevent zero pivot
matrix ordering: natural
factor fill ratio given 1, needed 1
Factored matrix follows:
Matrix Object: 1 MPI processes
type: seqaij
rows=0, cols=0
package used to perform factorization: petsc
total: nonzeros=0, allocated nonzeros=0
total number of mallocs used during MatSetValues calls =0
not using I-node routines
linear system matrix = precond matrix:
Matrix Object: 1 MPI processes
type: seqaij
rows=0, cols=0
total: nonzeros=0, allocated nonzeros=0
total number of mallocs used during MatSetValues calls =0
not using I-node routines
Split number 1 Defined by IS
KSP Object: (fieldsplit_Field_1_) 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_Field_1_) 1 MPI processes
type: ilu
ILU: out-of-place factorization
0 levels of fill
tolerance for zero pivot 2.22045e-14
using diagonal shift on blocks to prevent zero pivot
matrix ordering: natural
factor fill ratio given 1, needed 1
Factored matrix follows:
Matrix Object: 1 MPI processes
type: seqaij
rows=0, cols=0
package used to perform factorization: petsc
total: nonzeros=0, allocated nonzeros=0
total number of mallocs used during MatSetValues calls =0
not using I-node routines
linear system matrix = precond matrix:
Matrix Object: 1 MPI processes
type: seqaij
rows=0, cols=0
total: nonzeros=0, allocated nonzeros=0
total number of mallocs used during MatSetValues calls =0
not using I-node routines
Split number 2 Defined by IS
KSP Object: (fieldsplit_Field_2_) 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_Field_2_) 1 MPI processes
type: ilu
ILU: out-of-place factorization
0 levels of fill
tolerance for zero pivot 2.22045e-14
using diagonal shift on blocks to prevent zero pivot
matrix ordering: natural
factor fill ratio given 1, needed 1
Factored matrix follows:
Matrix Object: 1 MPI processes
type: seqaij
rows=0, cols=0
package used to perform factorization: petsc
total: nonzeros=0, allocated nonzeros=0
total number of mallocs used during MatSetValues calls =0
not using I-node routines
linear system matrix = precond matrix:
Matrix Object: 1 MPI processes
type: seqaij
rows=0, cols=0
total: nonzeros=0, allocated nonzeros=0
total number of mallocs used during MatSetValues calls =0
not using I-node routines
Split number 3 Defined by IS
KSP Object: (fieldsplit_Field_3_) 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_Field_3_) 1 MPI processes
type: ilu
ILU: out-of-place factorization
0 levels of fill
tolerance for zero pivot 2.22045e-14
using diagonal shift on blocks to prevent zero pivot
matrix ordering: natural
factor fill ratio given 1, needed 1
Factored matrix follows:
Matrix Object: 1 MPI processes
type: seqaij
rows=0, cols=0
package used to perform factorization: petsc
total: nonzeros=0, allocated nonzeros=0
total number of mallocs used during MatSetValues calls =0
not using I-node routines
linear system matrix = precond matrix:
Matrix Object: 1 MPI processes
type: seqaij
rows=0, cols=0
total: nonzeros=0, allocated nonzeros=0
total number of mallocs used during MatSetValues calls =0
not using I-node routines
linear system matrix = precond matrix:
Matrix Object: 1 MPI processes
type: seqaij
rows=16, cols=16
total: nonzeros=256, allocated nonzeros=256
total number of mallocs used during MatSetValues calls =0
using I-node routines: found 4 nodes, limit used is 5
I am also attaching part of my code which I use to generate the DM, the
KSP and the PC objects.
Best,
Luc
On 01/25/2014 10:31 AM, Matthew Knepley wrote:
> On Fri, Jan 24, 2014 at 5:10 PM, Luc Berger-Vergiat
> <lb2653 at columbia.edu <mailto:lb2653 at columbia.edu>> wrote:
>
> Hi all,
> I want to use PETSc as a solver for an FEM problem: modelization
> of shear bands using a 4 fields mixed formulation.
>
> So far I am just trying to set up a two fields in a Petsc section,
> assign dof too each field and then set up the section to pass it
> to a DM. I am taking this approach because in general I want for
> fieldsplit to work purely on the algebraic level without knowledge
> of boundary conditions or geometry.
>
> As of now I have issues when I try to assign a point and its
> associated degree of freedom to a field using:
> PetscSectionSetFieldDof.
> Is this the correct way to associate a dof/point to a field?
>
>
> You have to set the number of fields before the chart. I am updating
> the docs.
>
> Thanks,
>
> Matt
>
> I attached an example code and its makefile.
>
> --
> Best,
> Luc
>
>
>
>
> --
> 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
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