[petsc-users] the convergence of petsc iterative solver

[Debao Shao]

Dear all:

I'm using PETSC iterative solver(PCILU & KSPGMRES) in OOQP, but when the to be solved matrix is ill-posed, say condition number ~ 1e+4, then, KSPGMRES will exceed its maximal iteration number(default as 10000), while when I checked the same data with cholmod direct solver, it can solve the problem and return an answer correctly.

Does it mean the iterative solver(like GMRES) relies more on the well-pose matrix than cholmod direct solver?
How can I improve the case to avoid KSPGMRES fail case?

Your answer is appreciated.

Thanks,
Debao

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