Zero Pivot Row in LU Factorization

[Matthew Knepley]

On Nov 25, 2007 12:54 PM, Tim Stitt <timothy.stitt at ichec.ie> wrote:
> Hi all,
>
> Can anyone suggest ways of overcoming the following pivot error I keep
> receiving in my PETSc code during a KSPSolve().
>
> [1]PETSC ERROR: Detected zero pivot in LU factorization
> see
> http://www.mcs.anl.gov/petsc/petsc-as/documentation/troubleshooting.html#ZeroPivot!
> [1]PETSC ERROR: Zero pivot row 1801 value 0.00102826 tolerance
> 0.00165189 * rowsum 1.65189e+09!
>
>  From checking the documentation....the error is in row 1801, which
> means it is most likely not a matrix assembly issue?
>
> I tried the following prior to the solve with no luck either.....
>
> call KSPGetPC(ksp,pc,error)
> call PCFactorSetShiftNonzero(pc,PETSC_DECIDE,error)

I bet you are shifting the Block-Jacobi PC, not the LU PC which is the
subsolver.

   Matt

> Is there anything else I can try?
>
> Thanks,
>
> Tim.
>
> --
> Dr. Timothy Stitt <timothy_dot_stitt_at_ichec.ie>
> HPC Application Consultant - ICHEC (www.ichec.ie)
>
> Dublin Institute for Advanced Studies
> 5 Merrion Square - Dublin 2 - Ireland
>
> +353-1-6621333 (tel) / +353-1-6621477 (fax)
>
>



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