Variational problem in 2D, runtime error

Question

Hi
When i solving linear problem on mixedfunctionspace, it will solvable. Then try to find rate of convergence and errors, after that i will be able solve upto 64 mesh, then we try to solve 128 and 264, rate of convergence turn to fails.
Error occur it like

Solving linear variational problem.
Traceback (most recent call last):
[0]PETSC ERROR: --------------------- Error Message ------------------------------------
[0]PETSC ERROR: Error in external library!
[0]PETSC ERROR: umfpack_UMF_numeric failed!
[0]PETSC ERROR: ------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Release Version 3.2.0, Patch 5, Sat Oct 29 13:45:54 CDT 2011
[0]PETSC ERROR: See docs/changes/index.html for recent updates.
[0]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[0]PETSC ERROR: See docs/index.html for manual pages.
[0]PETSC ERROR: ------------------------------------------------------------------------

[0]PETSC ERROR: ------------------------------------------------------------------------
[0]PETSC ERROR: MatLUFactorNumeric_UMFPACK() line 204 in src/mat/impls/aij/seq/umfpack/umfpack.c
[0]PETSC ERROR: MatLUFactorNumeric() line 2876 in src/mat/interface/matrix.c
[0]PETSC ERROR: PCSetUp_LU() line 160 in src/ksp/pc/impls/factor/lu/lu.c
[0]PETSC ERROR: PCSetUp() line 819 in src/ksp/pc/interface/precon.c
[0]PETSC ERROR: KSPSetUp() line 260 in src/ksp/ksp/interface/itfunc.c
[0]PETSC ERROR: KSPSolve() line 379 in src/ksp/ksp/interface/itfunc.c

I wouldn't able to get an idea about this.

Anybody clarify this to me.

Thank you

Answer 1

PETSc builds UMFPACK with 32-bit integers, which severely limits the size problem that UMFPACK will solve. Build PETSc with SuperLU and MUMPS and experiment with these. You can choose the solver via the LUSover constructor.

Comments

So let me explain briefly in FEniCS with python format, but i seen in FEniCS page couldn't able to understand. Actually, So i need some demo format with boundary conditions like d6_p2D.py demo.