On Tue, Mar 30, 2010 at 3:49 PM, Nestor M. Solalinde <[email protected]> wrote: > Dear libmesh developers and users: > > I'm not been able to solve ex11 or ex13 using LU factorization. I get the > error shown below. Does this means the matrix is singular?? PETSC > documentation states "If this error occurs in the *zeroth row * of the > matrix it is likely you have an error in the code that generates the > matrix". What's happening?. I'm trying to understand this because I think it > might be related to a problem I'm having with a 2-phased incompressible flow > simulation code I'm writing.
I can get it to work with -pc_factor_shift_nonzero, which basically adds something to the diagonal during factorization so the pivots are nonzero. According to the PETSc docs, "A zero pivot in LU, ILU, Cholesky, or ICC sparse factorization does not always mean that the matrix is singular." And we shouldn't be in ex11 or ex13, since constant pressure vectors should be removed by pinning the pressure. Looks like this command line arg has been replaced as of 3.1 by -pc_factor_shift_type and -pc_factor_shift_amount. -- John ------------------------------------------------------------------------------ Download Intel® Parallel Studio Eval Try the new software tools for yourself. Speed compiling, find bugs proactively, and fine-tune applications for parallel performance. See why Intel Parallel Studio got high marks during beta. http://p.sf.net/sfu/intel-sw-dev _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
