Re: [Libmesh-users] Constrains using penalty

[Vasileios V. <va...@gm...>]

Hi

Can I naively ask how "big" the penalty factor introduced here is wrt the
mechanical stiffness?
Have you confirmed that it is (somehow) at least 5-6 orders of magnitude
bigger than the max element of the system matrix?

cheers,
Vas



On 6 October 2015 at 11:13, Вася Бубликов <gre...@gm...> wrote:

> Dear Sirs,
>
> I'm trying to make Libmesh work with a simple linear elasticity problem
> using linear systems example 4 as an example. I need to force the top
> boundary remain flat, i.e. all normal displacements are of the same value
> to be computed.
> To obtain this, for example to make the displacements for DOFs i1,i2,i3..in
> the same as for the DOF j, I add penalty (1e10) to K(in,in) and subtract it
> from K(in,j) meaning to add 1e10*(U_in - U_j) = 0 to the  in'th equation
> in the assembly function. But as soon as in and j are on different finite
> elements I get the same error no matter which particular c++ function I use
> (system.matrix->add(i,j,value)   system.matrix->add_matrix(DenseMatrix)
> or system.matrix->add(SparseMatrix) ). I would be very mush obliged if you
> helped me.
>
> Kind regards,
> Roman Khudobin
> Research Assistant ICHPH RAS
>
> [0]PETSC ERROR: --------------------- Error Message
> --------------------------------------------------------------
> [0]PETSC ERROR: Argument out of range
> [0]PETSC ERROR: New nonzero at (17,47) caused a malloc
> Use MatSetOption(A, MAT_NEW_NONZERO_ALLOCATION_ERR, PETSC_FALSE) to turn
> off this check
> [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html
> for
> trouble shooting.
> [0]PETSC ERROR: Petsc Release Version 3.6.1, Jul, 22, 2015
> [0]PETSC ERROR: ./constrain.o on a arch-linux-c-opt named izmailovo by
> gream Tue Oct  6 12:55:21 2015
> [0]PETSC ERROR: Configure options --prefix=/opt/petsc/linux-c-opt
> --PETSC_ARCH=arch-linux-c-opt --with-shared-libraries=1 --COPTFLAGS=-O3
> --CXXOPTFLAGS=-O3 --with-mumps=1 --with-hdf5=1 --with-scalapack=1
> --with-suitesparse=1 --with-metis=1 --with-parmetis=1 --with-ptscotch=1
>
> --with-ptscotch-lib="[libesmumps.so,libptscotch.so,libptscotcherr.so,libscotch.so,libscotcherr.so,libbz2.so]"
> --with-ptscotch-include=/usr/include/scotch --with-superlu=1
> --with-superlu-lib=-lsuperlu --with-superlu-include=/usr/include/superlu
> --with-ml=1
> [0]PETSC ERROR: #1 MatSetValues_SeqAIJ() line 485 in
> /tmp/yaourt-tmp-gream/aur-petsc/src/petsc-3.6.1/src/mat/impls/aij/seq/aij.c
> [0]PETSC ERROR: #2 MatSetValues() line 1173 in
> /tmp/yaourt-tmp-gream/aur-petsc/src/petsc-3.6.1/src/mat/interface/matrix.c
> --------------------------------------------------------------------------
> MPI_ABORT was invoked on rank 0 in communicator MPI_COMM_WORLD
> with errorcode 1.
>
> NOTE: invoking MPI_ABORT causes Open MPI to kill all MPI processes.
> You may or may not see output from other processes, depending on
> exactly when Open MPI kills them.
> --------------------------------------------------------------------------
>
>
> ------------------------------------------------------------------------------
>
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