PCGASMSetSubdomains#

Sets the subdomains for this MPI rank for the additive Schwarz preconditioner with multiple MPI ranks per subdomain, PCGASM

Synopsis#

#include "petscpc.h" 
PetscErrorCode PCGASMSetSubdomains(PC pc, PetscInt n, IS iis[], IS ois[])

Collective

Input Parameters#

pc - the preconditioner object
n - the number of subdomains for this MPI rank
iis - the index sets that define the inner subdomains (or NULL for PETSc to determine subdomains)
ois - the index sets that define the outer subdomains (or NULL to use the same as iis, or to construct by expanding iis by the requested overlap)

Notes#

The IS indices use the parallel, global numbering of the vector entries.

Inner subdomains are those where the correction is applied.

Outer subdomains are those where the residual necessary to obtain the corrections is obtained (see PCGASMType for the use of inner/outer subdomains).

Both inner and outer subdomains can extend over several MPI ranks. This rank’s portion of a subdomain is known as a local subdomain.

Inner subdomains can not overlap with each other, do not have any entities from remote ranks, and have to cover the entire local subdomain owned by the current rank. The index sets on each rank should be ordered such that the ith local subdomain is connected to the ith remote subdomain on another MPI rank.

By default the PGASM preconditioner uses 1 (local) subdomain per MPI rank.

The iis and ois arrays may be freed after this call using PCGASMDestroySubdomains()