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
See Also#
KSP: Linear System Solvers, PCEISENSTAT
, PCSORGetOmega()
, PCEisenstatSetOmega()
Level#
intermediate
Location#
Implementations#
PCEisenstatGetOmega_Eisenstat() in src/ksp/pc/impls/eisens/eisen.c
Index of all PC routines
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Index of all manual pages