KSPSetPCSide#

Sets the preconditioning side.

Synopsis#

#include "petscksp.h" 
#include "petscmat.h" 
PetscErrorCode KSPSetPCSide(KSP ksp, PCSide side)

Logically Collective

Input Parameter#

ksp - iterative solver obtained from KSPCreate()

Output Parameter#

side - the preconditioning side, where side is one of

  PC_LEFT      - left preconditioning (default)
  PC_RIGHT     - right preconditioning
  PC_SYMMETRIC - symmetric preconditioning

Options Database Key#

-ksp_pc_side <right,left,symmetric> - KSP preconditioner side

Notes#

Left preconditioning is used by default for most Krylov methods except KSPFGMRES which only supports right preconditioning.

For methods changing the side of the preconditioner changes the norm type that is used, see KSPSetNormType().

Symmetric preconditioning is currently available only for the KSPQCG method. However, note that symmetric preconditioning can be emulated by using either right or left preconditioning, modifying the application of the matrix (with a custom Mat argument to KSPSetOperators(), and using a pre ‘KSPSetPreSolve()or post processingKSPSetPostSolve()` step).

Setting the PCSide often affects the default norm type. See KSPSetNormType() for details.

Level#

intermediate

Location#

src/ksp/ksp/interface/itfunc.c

Index of all KSP routines
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Index of all manual pages