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Subsection 9.2.2: Skyline Up Section 9.2: Configuring Linear Solvers Subsection 9.2.4: CG

9.2.3 FGMRES

This iterative linear solver, from the MKL library, implements the GMRES algorithm, which is an efficient Krylov-based iterative solution strategy. It requires several configuration parameters, listed below, and only works with unsymmetric matrices. In the table below, N refers to the number of equations.
 parameter description default max_iter The maximum number of iterations min(N,150) tol relative residual tolerance 1e-6 abs_tol absolute residual tolerance 1e-12 print_level The amount of information printed (0,1, or 2) 0 fail_max_iters Indicates whether reaching max iters is a failure or not (1) 1 (true) pc_left The left preconditioner (none) pc_right The right preconditioner (none)
Comments:
1. When using FGMRES as a preconditioner it is recommended to set the fail_max_iters flag to zero.
Subsection 9.2.2: Skyline Up Section 9.2: Configuring Linear Solvers Subsection 9.2.4: CG