PETSc version 3.17.4
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# PCSORGetSymmetric

Gets the form the SOR preconditioner is using; backward, or forward relaxation. The local variants perform SOR on each processor. By default forward relaxation is used.

### Synopsis

    #include "petscpc.h"
    PetscErrorCode  PCSORGetSymmetric(PC pc,MatSORType *flag)

Logically Collective on PC

### Input Parameter

| pc | - the preconditioner context

### Output Parameter

| flag | - one of the following

        SOR_FORWARD_SWEEP
        SOR_BACKWARD_SWEEP
        SOR_SYMMETRIC_SWEEP
        SOR_LOCAL_FORWARD_SWEEP
        SOR_LOCAL_BACKWARD_SWEEP
        SOR_LOCAL_SYMMETRIC_SWEEP

### Options Database Keys

| -pc_sor_symmetric | - Activates symmetric version
| -pc_sor_backward | - Activates backward version
| -pc_sor_local_forward | - Activates local forward version
| -pc_sor_local_symmetric | - Activates local symmetric version
| -pc_sor_local_backward | - Activates local backward version

### Notes

To use the Eisenstat trick with SSOR, employ the PCEISENSTAT preconditioner, which can be chosen with the option

| -pc_type eisenstat | - Activates Eisenstat trick

### See Also

PCEisenstatSetOmega(), PCSORSetIterations(), PCSORSetOmega(), PCSORSetSymmetric()

### Level

intermediate

### Location

src/ksp/pc/impls/sor/sor.c

### Implementations

PCSORGetSymmetric_SOR in src/ksp/pc/impls/sor/sor.c
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