PCGAMGSetUseSAEstEig#

Use the eigen estimate from smoothed aggregation for the Chebyshev smoother during the solution process

Synopsis#

#include "petscpc.h" 
#include "petscksp.h" 
PetscErrorCode PCGAMGSetUseSAEstEig(PC pc, PetscBool b)

Collective

Input Parameters#

pc - the preconditioner context
b - flag

Options Database Key#

-pc_gamg_use_sa_esteig <true,false> - use the eigen estimate

Notes#

Smoothed aggregation constructs the smoothed prolongator \(P = (I - \omega D^{-1} A) T\) where \(T\) is the tentative prolongator and \(D\) is the diagonal of \(A\). Eigenvalue estimates (based on a few PCCG or PCGMRES iterations) are computed to choose \(\omega\) so that this is a stable smoothing operation. If KSPCHEBYSHEV with PCJACOBI (diagonal) preconditioning is used for smoothing on the finest level, then the eigenvalue estimates can be reused during the solution process. This option is only used when the smoother uses PCJACOBI, and should be turned off when a different PCJacobiType is used. It became default in PETSc 3.17.