KSPGMRES#

Implements the Generalized Minimal Residual method. (Saad and Schultz, 1986) with restart

Options Database Keys#

-ksp_gmres_restart

the number of Krylov directions to orthogonalize against

-ksp_gmres_haptol

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 <refine_never,refine_ifneeded,refine_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

Notes#

Left and right preconditioning are supported, but not symmetric preconditioning.

References#

: YOUCEF SAAD AND MARTIN H. SCHULTZ, GMRES: A GENERALIZED MINIMAL RESIDUAL ALGORITHM FOR SOLVING NONSYMMETRIC LINEAR SYSTEMS. SIAM J. ScI. STAT. COMPUT. Vo|. 7, No. 3, July 1986.

See Also#

KSPCreate(), KSPSetType(), KSPType, KSP, KSPFGMRES, KSPLGMRES, KSPGMRESSetRestart(), KSPGMRESSetHapTol(), KSPGMRESSetPreAllocateVectors(), KSPGMRESSetOrthogonalization(), KSPGMRESGetOrthogonalization(), KSPGMRESClassicalGramSchmidtOrthogonalization(), KSPGMRESModifiedGramSchmidtOrthogonalization(), KSPGMRESCGSRefinementType, KSPGMRESSetCGSRefinementType(), KSPGMRESGetCGSRefinementType(), KSPGMRESMonitorKrylov(), KSPSetPCSide()

Level#

beginner

Location#

src/ksp/ksp/impls/gmres/gmres.c

Examples#

src/ksp/ksp/tutorials/ex62.c.html
src/ksp/ksp/tutorials/ex78.c.html
src/ksp/ksp/tutorials/ex7.c.html
src/ksp/ksp/tutorials/ex7f.F90.html
src/ksp/ksp/tutorials/ex8.c.html
src/tao/pde_constrained/tutorials/hyperbolic.c.html


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