This is because on many processes I believe you are running Block-Jacobi with LU on the diagonal blocks. It is easy for one of these blocks to be singular.
Matt On Nov 25, 2007 1:10 PM, Tim Stitt <timothy.stitt at ichec.ie> wrote: > I should also add that the code executes without this error when using 1 > processor...but then displays the error when running in parallel with > more than one process. > > Tim Stitt 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) > > > > > 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) > > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener
