[petsc-users] MINRES accuracy for a SPD matrix

[Mohammad Gohardoust]

Hi,

I am trying to evaluate different solver/preconditioner combinations for
solving Richards' equation in porous media. The coefficient matrix is
symmetric positive definite and is usually solved by CG solver. I tried
MINRES with various preconditioners. The solution is acceptable but with
somehow considerable errors (compared to other solvers) which requires me
to decrease the tolerance threshold in my Picard iteration leading to
larger computation time. I would like to know if this is common for MINRES
and how to possibly overcome this?

Thanks,
Mohammad
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