petsc-3.8.4 2018-03-24

PCModifySubMatrices

Calls an optional user-defined routine within certain preconditioners if one has been set with PCSetModifySubMarices().

Synopsis

#include "petscksp.h" 
PetscErrorCode  PCModifySubMatrices(PC pc,PetscInt nsub,const IS row[],const IS col[],Mat submat[],void *ctx)

Collective on PC

Input Parameters

	pc	- the preconditioner context
	nsub	- the number of local submatrices
	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 routine (may be null)

Output Parameter

submat -array of local submatrices (the entries of which may have been modified)

Notes

The user should NOT generally call this routine, as it will automatically be called within certain preconditioners (currently block Jacobi, additive Schwarz) if set.

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.

Keywords