Error in "amg" possion solver

Question

Here is my code:

for i in range(6):
    for j in range(i+1):

        tmpb=frx[i]*frx[j]*v*dx
        a=0.25/pi*inner(nabla_grad(u), nabla_grad(v))*dx
        if i==j:
            problem = LinearVariationalProblem(a, tmpb, tmpf, bc1)
        else:
            problem = LinearVariationalProblem(a, tmpb, tmpf, bc)
        solver = LinearVariationalSolver(problem)
        solver.parameters["linear_solver"] = "cg"
        solver.parameters["preconditioner"] = "amg"
        solver.solve()
        vpo[findex(i,j)]=tmpf

I always get such error after 8 successful solvers:

Solving linear variational problem.
Solving linear variational problem.
Solving linear variational problem.
Solving linear variational problem.
Solving linear variational problem.
Solving linear variational problem.
Solving linear variational problem.
[0]PETSC ERROR: --------------------- Error Message ------------------------------------
[0]PETSC ERROR: Error in external library!
[0]PETSC ERROR: Error in HYPRE solver, error code 1!
[0]PETSC ERROR: ------------------------------------------------------------------------
[0]PETSC ERROR: Petsc Release Version 3.1.0, Patch 8, Thu Mar 17 13:37:48 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: Unknown Name on a linux-gnu named sobolev by vincehouhou Wed Jun 18 21:19:16 2014
[0]PETSC ERROR: Libraries linked from /build/buildd/petsc-3.1.dfsg/linux-gnu-c-opt/lib
[0]PETSC ERROR: Configure run at Mon Jan 2 08:46:13 2012
[0]PETSC ERROR: Configure options --with-shared --with-debugging=0 --useThreads 0 --with-clanguage=C++ --with-c-support --with-fortran-interfaces=1 --with-mpi-dir=/usr/lib/openmpi --with-mpi-shared=1 --with-blas-lib=-lblas --with-lapack-lib=-llapack --with-blacs=1 --with-blacs-include=/usr/include --with-blacs-lib="[/usr/lib/libblacsCinit-openmpi.so,/usr/lib/libblacs-openmpi.so]" --with-scalapack=1 --with-scalapack-include=/usr/include --with-scalapack-lib=/usr/lib/libscalapack-openmpi.so --with-mumps=1 --with-mumps-include=/usr/include --with-mumps-lib="[/usr/lib/libdmumps.so,/usr/lib/libzmumps.so,/usr/lib/libsmumps.so,/usr/lib/libcmumps.so,/usr/lib/libmumps_common.so,/usr/lib/libpord.so]" --with-umfpack=1 --with-umfpack-include=/usr/include/suitesparse --with-umfpack-lib="[/usr/lib/libumfpack.so,/usr/lib/libamd.so]" --with-spooles=1 --with-spooles-include=/usr/include/spooles --with-spooles-lib=/usr/lib/libspooles.so --with-hypre=1 --with-hypre-dir=/usr --with-scotch=1 --with-scotch-include=/usr/include/scotch --with-scotch-lib=/usr/lib/libscotch.so --with-hdf5=1 --with-hdf5-dir=/usr
[0]PETSC ERROR: ------------------------------------------------------------------------
[0]PETSC ERROR: PCApply_HYPRE() line 181 in src/ksp/pc/impls/hypre/hypre.c
[0]PETSC ERROR: PCApply() line 357 in src/ksp/pc/interface/precon.c
[0]PETSC ERROR: KSPSolve_CG() line 153 in src/ksp/ksp/impls/cg/cg.c
[0]PETSC ERROR: KSPSolve() line 396 in src/ksp/ksp/interface/itfunc.c
[0]PETSC ERROR: PCDestroy_HYPRE() line 201 in src/ksp/pc/impls/hypre/hypre.c
[0]PETSC ERROR: PCDestroy() line 83 in src/ksp/pc/interface/precon.c
[0]PETSC ERROR: KSPDestroy() line 695 in src/ksp/ksp/interface/itfunc.c

I have checked all of my functions "frx" are right. Any suggestions? Thanks.

Have you tried other solver / preconditioner pairs? Specifically, I'm wondering if gmres would do it for the solver.
Does AMG preserve the symmetry of the system matrix? If not, I think that would cause CG to fail no? — mwelland, Jun 19, 2014

Error in "amg" possion solver

1 Answer