[petsc-users] GAMG for the unsymmetrical matrix

[Kong, Fande]

Hi All,

I am using GAMG to solve a group of coupled diffusion equations, but the
resulting matrix is not symmetrical. I got the following error messages:













*[0]PETSC ERROR: Petsc has generated inconsistent data[0]PETSC ERROR: Have
un-symmetric graph (apparently). Use '-pc_gamg_sym_graph true' to symetrize
the graph or '-pc_gamg_threshold -1.0' if the matrix is structurally
symmetric.[0]PETSC ERROR: See
http://www.mcs.anl.gov/petsc/documentation/faq.html
<http://www.mcs.anl.gov/petsc/documentation/faq.html> for trouble
shooting.[0]PETSC ERROR: Petsc Release Version 3.7.5, unknown [0]PETSC
ERROR: /home/kongf/workhome/projects/yak/yak-opt on a arch-linux2-c-opt
named r2i2n0 by kongf Mon Apr  3 16:19:59 2017[0]PETSC ERROR:
/home/kongf/workhome/projects/yak/yak-opt on a arch-linux2-c-opt named
r2i2n0 by kongf Mon Apr  3 16:19:59 2017[0]PETSC ERROR: #1 smoothAggs()
line 462 in
/home/kongf/workhome/projects/petsc/src/ksp/pc/impls/gamg/agg.c[0]PETSC
ERROR: #2 PCGAMGCoarsen_AGG() line 998 in
/home/kongf/workhome/projects/petsc/src/ksp/pc/impls/gamg/agg.c[0]PETSC
ERROR: #3 PCSetUp_GAMG() line 571 in
/home/kongf/workhome/projects/petsc/src/ksp/pc/impls/gamg/gamg.c[0]PETSC
ERROR: #3 PCSetUp_GAMG() line 571 in
/home/kongf/workhome/projects/petsc/src/ksp/pc/impls/gamg/gamg.c*
Does this mean that GAMG works for the symmetrical matrix only?

Fande,
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