PCEisenstatGetOmega#

Gets the SSOR relaxation coefficient, omega, to use with Eisenstat’s trick (where omega = 1.0 by default).

Synopsis#

#include "petscpc.h" 
PetscErrorCode PCEisenstatGetOmega(PC pc, PetscReal *omega)

Logically Collective

Input Parameter#

pc - the preconditioner context

Output Parameter#

omega - relaxation coefficient (0 < omega < 2)

Options Database Key#

-pc_eisenstat_omega - Sets omega

Notes#

The Eisenstat trick implementation of SSOR requires about 50% of the usual amount of floating point operations used for SSOR + Krylov method; however, the preconditioned problem must be solved with both left and right preconditioning.

To use SSOR without the Eisenstat trick, employ the PCSOR preconditioner, which can be chosen with the database options -pc_type sor -pc_sor_symmetric