solving a particular linear equation system
Christian May
cmay at phys.ethz.ch
Fri May 15 14:29:09 CDT 2009
Hi everybody,
I have trouble solving a linear equation system with PETSc 3.0.0.
I tried the following combinations of solvers and preconditioners and list
the results:
cg+sor: Linear solve did not converge due to DIVERGED_NAN
cg+bjacobi: Linear solve did not converge due to DIVERGED_INDEFINITE_PC
cg+ilu: Linear solve did not converge due to DIVERGED_INDEFINITE_MAT
gmres+sor: Linear solve did not converge due to DIVERGED_NAN
gmres+bjacobi:Linear solve did not converge due to DIVERGED_ITS
gmres+ilu: Linear solve did not converge due to DIVERGED_ITS
It might be that the matrix is not positive definite, which explains
some of the problems. In the last two cases it kind of works, but convergence
is horribly slow and it aborts after 10000 iterations.
If somebody could please have a look at the matrix and the right hand side
vector, I've put them here:
http://www.mayarea.de/download/small_matrix.tgz
The archive contains a file named A.txt, consisting of three columns
i j Aij and a file b.txt with two columns i and bi.
Any hint on how to solve this linear equation system (in reasonable time)
is appreciated.
Thanks a lot in advance!
Christian
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