[petsc-users] Zero diagonal term for direct solver

[Qin Lu via petsc-users]

Hello,
I am using the Petsc native direct solver (with KSPPREONLY and PCLU) to solver 
a small Linear equation system. The matrix has a couple of diagonal terms with 
value 0, which makes the solver fail. Then I set a very small value (e.g., 
1e-10) at these terms and the solver works. Can this cause noticeable errors in 
the solution? Are there any options in Petsc to make the direct solver do 
row/column pivoting so that all the diagonal terms are non-zero?
Thanks for any suggestions.
Regards,Qin