After I run the app as you suggested I still get the same error. I have also tried other options: '-pc_factor_shift_type NONZERO -pc_factor_shift_amount [amount]' or '-pc_factor_shift_type POSITIVE_DEFINITE'; '-[level]_pc_factor_shift_type NONZERO -pc_factor_shift_amount [amount]' or '-[level]_pc_factor_shift_type POSITIVE_DEFINITE' to prevent the zero pivot.
without luck. Strange thing is that after I generate the A and B matrices and use PySparse to solve the GEP it works fine. Nevertheless I ll play around with the code and try to find out where I went wrong. Thank you P On Thu, Jan 24, 2013 at 12:36 PM, Kirk, Benjamin (JSC-EG311) < [email protected]> wrote: > On Jan 24, 2013, at 2:29 PM, Peter Zajac <[email protected]> wrote: > > > According to the PETSC documentation zero pivot does not always mean the > > matrix is singular and since I am getting the correct results I am > ignoring > > the error. Could my ignorance in this case cause a serious problem in the > > future I should be aware of? > > > > thank you again > > Previously Roy mentioned penalty vs Dirichlet boundary conditions? > > Penalty boundary conditions sometimes can cause an issue like this, as can > disparate scaling in variables. > > What happens if you pass > > '-pc_factor_zeropivot 0 -sub_pc_factor_zeropivot 0' > > to your application? Do you still get that message? > > PETSc has a default tolerance that it considers '0' during the > factorization, these options override that default. > > -Ben > > > ------------------------------------------------------------------------------ Master Visual Studio, SharePoint, SQL, ASP.NET, C# 2012, HTML5, CSS, MVC, Windows 8 Apps, JavaScript and much more. Keep your skills current with LearnDevNow - 3,200 step-by-step video tutorials by Microsoft MVPs and experts. ON SALE this month only -- learn more at: http://p.sf.net/sfu/learnnow-d2d _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
