Barry, I will be using these routines from Fortran..so I am assuming that Fortran interfaces are available for each routine?
Also, how do I know how many sub ksp's there will be? I am assuming I need to dynamically allocate the subksp array in Fortran but do I know the size in advance? Is this related to the value 'n' ? If so, how do I calculate 'n'. What is the significance of subksp[0]? Is it just the sub ksp at this position I should be interested in? Finally, which of the PCFactorSetxxxxxx routines should I be using? Sorry for the twenty questions (well nearly) but I am just a bit confused with this approach. Thanks, Tim. Barry Smith wrote: > > KSP *subksp; > > KSPGetPC(ksp,pc) > PCBJacobiGetSubKSP(pc,&n,PETSC_NULL,&subksp) > KSPGetPC(subksp[0],&subpc); > PCFactorSetxxxxxx(subpc, .... > > Barry > > > On Nov 25, 2007, at 1:10 PM, Tim Stitt 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) >> > -- 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)
