[petsc-users] Very low CFL number for PETSC's GS

[Orxan Shibliyev]

I wanted to compare my own GS and the one of PETSC's. I used KSPRICHARDSON
with PCSOR to obtain GS. I tested my GS with CFL=40 and solved Ax=b problem
successfully and fast. However, PETSC failed to solve at CFL=40 and it
gives an answer only for very low CFL numbers such as 0.1. Of course, the
convergence was very slow. My question is that if A and b and the
implementations are the same why PETSC fails to solve with same CFL number
as for my GS solver?

PS1: My GS solver is a plain GS, no fancy stuff.
PS2: A is a block matrix (MATSEQBAIJ) for PETSC. Also, the process is
sequential.
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