petscmaster 20201130
PCEisenstatSetOmega
Sets the SSOR relaxation coefficient, omega, to use with Eisenstat's trick (where omega = 1.0 by default).
Synopsis
#include "petscpc.h"
PetscErrorCode PCEisenstatSetOmega(PC pc,PetscReal omega)
Logically Collective on PC
Input Parameters
 pc   the preconditioner context

 omega   relaxation coefficient (0 < omega < 2)

Options Database Key
 pc_eisenstat_omega <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
See Also
PCSORSetOmega()
Level
intermediate
Location
src/ksp/pc/impls/eisens/eisen.c
Implementations
PCEisenstatSetOmega_Eisenstat in src/ksp/pc/impls/eisens/eisen.c
Index of all PC routines
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