PETSc version 3.17.2
Fix/Edit manual page

MatSchurComplementGetPmat

Obtain a preconditioning matrix for the Schur complement by assembling Sp = A11 - A10 inv(DIAGFORM(A00)) A01

Synopsis

#include "petscksp.h" 
PetscErrorCode  MatSchurComplementGetPmat(Mat S,MatReuse preuse,Mat *Sp)
Collective on S

Input Parameters

S - matrix obtained with MatCreateSchurComplement() (or equivalent) that implements the action of A11 - A10 ksp(A00,Ap00) A01
preuse - MAT_INITIAL_MATRIX for a new Sp, or MAT_REUSE_MATRIX to reuse an existing Sp, or MAT_IGNORE_MATRIX to put nothing in Sp

Output Parameter

Sp - approximate Schur complement suitable for preconditioning the exact Schur complement S = A11 - A10 inv(A00) A01

Note

The approximation of Sp depends on the the argument passed to to MatSchurComplementSetAinvType() MAT_SCHUR_COMPLEMENT_AINV_DIAG, MAT_SCHUR_COMPLEMENT_AINV_LUMP, or MAT_SCHUR_COMPLEMENT_AINV_BLOCK_DIAG or -mat_schur_complement_ainv_type <diag,lump,blockdiag>

Sometimes users would like to provide problem-specific data in the Schur complement, usually only for special row and column index sets. In that case, the user should call PetscObjectComposeFunction() to set "MatSchurComplementGetPmat_C" to their function. If their function needs to fall back to the default implementation, it should call MatSchurComplementGetPmat_Basic().

Developer Notes

The API that includes MatGetSchurComplement(), MatCreateSchurComplement(), MatSchurComplementGetPmat() should be refactored to remove redundancy and be clearer and simpler.

This routine should be called MatSchurComplementCreatePmat()

See Also

MatCreateSubMatrix(), PCFIELDSPLIT, MatGetSchurComplement(), MatCreateSchurComplement(), MatSchurComplementSetAinvType()

Level

advanced

Location

src/ksp/ksp/utils/schurm/schurm.c
Index of all KSP routines
Table of Contents for all manual pages
Index of all manual pages