solving a particular linear equation system

[Christian May]

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