PCSetModifySubMatrices#

Sets a user-defined routine for modifying the submatrices that arise within certain subdomain-based preconditioners. The basic submatrices are extracted from the preconditioner matrix as usual; the user can then alter these (for example, to set different boundary conditions for each submatrix) before they are used for the local solves.

Synopsis#

#include "petscksp.h" 
PetscErrorCode PCSetModifySubMatrices(PC pc, PetscErrorCode (*func)(PC, PetscInt, const IS[], const IS[], Mat[], void *), void *ctx)

Logically Collective

Input Parameters#

pc - the preconditioner context
func - routine for modifying the submatrices
ctx - optional user-defined context (may be null)

Calling sequence of `func`#

PetscErrorCode func(PC pc, PetscInt nsub, IS *row, IS *col, Mat *submat, void *ctx);

pc - the preconditioner context
row - an array of index sets that contain the global row numbers that comprise each local submatrix
col - an array of index sets that contain the global column numbers that comprise each local submatrix
submat - array of local submatrices
ctx - optional user-defined context for private data for the user-defined func routine (may be null)

Notes#

PCSetModifySubMatrices() MUST be called before KSPSetUp() and KSPSolve().

A routine set by PCSetModifySubMatrices() is currently called within the block Jacobi (PCBJACOBI) and additive Schwarz (PCASM) preconditioners. All other preconditioners ignore this routine.