petsc-3.7.5 2017-01-01

PCGASMSetOverlap

Sets the overlap between a pair of subdomains for the additive Schwarz preconditioner. Either all or no processors in the pc communicator must call this routine.

Synopsis

#include "petscpc.h" 
PetscErrorCode  PCGASMSetOverlap(PC pc,PetscInt ovl)

Logically Collective on pc

Input Parameters

	pc	- the preconditioner context
	ovl	- the amount of overlap between subdomains (ovl >= 0, default value = 0)

Options Database Key

-pc_gasm_overlap <overlap> -Sets overlap

Notes

By default the GASM preconditioner uses 1 subdomain per processor. To use multiple subdomain per perocessor or "straddling" subdomains that intersect multiple processors use PCGASMSetSubdomains() (or option -pc_gasm_total_subdomains <n>).

The overlap defaults to 0, so if one desires that no additional overlap be computed beyond what may have been set with a call to PCGASMSetSubdomains(), then ovl must be set to be 0. In particular, if one does not explicitly set the subdomains in application code, then all overlap would be computed internally by PETSc, and using an overlap of 0 would result in an GASM variant that is equivalent to the block Jacobi preconditioner.

Note that one can define initial index sets with any overlap via PCGASMSetSubdomains(); the routine PCGASMSetOverlap() merely allows PETSc to extend that overlap further, if desired.

Keywords

PC, GASM, set, overlap

Examples

src/ksp/ksp/examples/tutorials/ex62.c.html