#include "petscpc.h" PetscErrorCode PCFieldSplitSetSchurPre(PC pc,PCFieldSplitSchurPreType ptype,Mat pre)Collective on PC
| pc | - the preconditioner context | |
| ptype | - which matrix to use for preconditioning the Schur complement: PC_FIELDSPLIT_SCHUR_PRE_A11 (default), PC_FIELDSPLIT_SCHUR_PRE_SELF, PC_FIELDSPLIT_PRE_USER | |
| userpre | - matrix to use for preconditioning, or NULL |
If ptype is
user then the preconditioner for the Schur complement is generated by the provided matrix (pre argument
to this function).
a11 then the preconditioner for the Schur complement is generated by the block diagonal part of the preconditioner
matrix associated with the Schur complement (i.e. A11), not he Schur complement matrix
full then the preconditioner uses the exact Schur complement (this is expensive)
self the preconditioner for the Schur complement is generated from the Schur complement matrix itself:
The only preconditioner that currently works directly with the Schur complement matrix object is the PCLSC
preconditioner
selfp then the preconditioning matrix is an explicitly-assembled approximation Sp = A11 - A10 inv(diag(A00)) A01
This is only a good preconditioner when diag(A00) is a good preconditioner for A00. Optionally, A00 can be
lumped before extracting the diagonal: -fieldsplit_1_mat_schur_complement_ainv_type lump; diag is the default.
When solving a saddle point problem, where the A11 block is identically zero, using a11 as the ptype only makes sense with the additional option -fieldsplit_1_pc_type none. Usually for saddle point problems one would use a ptype of self and -fieldsplit_1_pc_type lsc which uses the least squares commutator to compute a preconditioner for the Schur complement.
Level:intermediate
Location:src/ksp/pc/impls/fieldsplit/fieldsplit.c
Index of all PC routines
Table of Contents for all manual pages
Index of all manual pages