petsc-3.9.4 2018-09-11
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Implements the Flexible Generalized Minimal Residual method. developed by Saad with restart

Options Database Keys

-ksp_gmres_restart <restart> - the number of Krylov directions to orthogonalize against
-ksp_gmres_haptol <tol> - sets the tolerance for "happy ending" (exact convergence)
-ksp_gmres_preallocate - preallocate all the Krylov search directions initially (otherwise groups of vectors are allocated as needed)
-ksp_gmres_classicalgramschmidt - use classical (unmodified) Gram-Schmidt to orthogonalize against the Krylov space (fast) (the default)
-ksp_gmres_modifiedgramschmidt - use modified Gram-Schmidt in the orthogonalization (more stable, but slower)
-ksp_gmres_cgs_refinement_type <never,ifneeded,always> - determine if iterative refinement is used to increase the stability of the classical Gram-Schmidt orthogonalization.
-ksp_gmres_krylov_monitor - plot the Krylov space generated
-ksp_fgmres_modifypcnochange - do not change the preconditioner between iterations
-ksp_fgmres_modifypcksp - modify the preconditioner using KSPFGMRESModifyPCKSP()

Notes: See KSPFGMRESSetModifyPC() for how to vary the preconditioner between iterations Only right preconditioning is supported.

Notes: The following options -ksp_type fgmres -pc_type ksp -ksp_ksp_type bcgs -ksp_view -ksp_pc_type jacobi make the preconditioner (or inner solver) be bi-CG-stab with a preconditioner of Jacobi.

Developer Notes: This object is subclassed off of KSPGMRES

See Also

KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPGMRES, KSPLGMRES,
KSPGMRESSetRestart(), KSPGMRESSetHapTol(), KSPGMRESSetPreAllocateVectors(), KSPGMRESSetOrthogonalization(), KSPGMRESGetOrthogonalization(), KSPGMRESClassicalGramSchmidtOrthogonalization(), KSPGMRESModifiedGramSchmidtOrthogonalization(), KSPGMRESCGSRefinementType, KSPGMRESSetCGSRefinementType(), KSPGMRESGetCGSRefinementType(), KSPGMRESMonitorKrylov(), KSPFGMRESSetModifyPC(), KSPFGMRESModifyPCKSP()




Index of all KSP routines
Table of Contents for all manual pages
Index of all manual pages