#include "petscpc.h" PetscErrorCode PCGASMSetOverlap(PC pc,PetscInt ovl)Logically Collective on pc
|pc||- the preconditioner context|
|ovl||- the amount of overlap between subdomains (ovl >= 0, default value = 0)|
|-pc_gasm_overlap <overlap>||- Sets overlap|
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.