petsc-3.14.6 2021-03-30

KSPGMRESClassicalGramSchmidtOrthogonalization

This is the basic orthogonalization routine using classical Gram-Schmidt with possible iterative refinement to improve the stability

PetscErrorCode  KSPGMRESClassicalGramSchmidtOrthogonalization(KSP ksp,PetscInt it)

Collective on ksp

	ksp	- KSP object, must be associated with GMRES, FGMRES, or LGMRES Krylov method
	its	- one less then the current GMRES restart iteration, i.e. the size of the Krylov space

	-ksp_gmres_classicalgramschmidt	- Activates KSPGMRESClassicalGramSchmidtOrthogonalization()
	-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.

Use KSPGMRESSetCGSRefinementType() to determine if iterative refinement is to be used. This is much faster than KSPGMRESModifiedGramSchmidtOrthogonalization() but has the small possibility of stability issues that can usually be handled by using a a single step of iterative refinement with KSPGMRESSetCGSRefinementType()

intermediate