solving a particular linear equation system
Barry Smith
bsmith at mcs.anl.gov
Fri May 15 15:11:49 CDT 2009
Could you please save this matrix and right hand side using -
ksp_view_binary (just run solver like you usually do but use this
command line option also) then post the file binaryoutput that is
generated. This way people can trivially load the matrix and right
hand side with MatLoad() and not monkey with parsing ASCII files.
Thanks
Barry
On May 15, 2009, at 2:29 PM, Christian May wrote:
> 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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