PCEisenstatSetOmega

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

Synopsis

#include "petscpc.h" 
int PCEisenstatSetOmega(PC pc,PetscReal omega)

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

Keywords