PCGASM#

Use the (restricted) additive Schwarz method, each block is (approximately) solved with its own KSP object on a subset of MPI ranks

Options Database Keys#

-pc_gasm_total_subdomains - Sets total number of local subdomains to be distributed among MPI ranks
-pc_gasm_view_subdomains - activates the printing of subdomain indices in PCView(), -ksp_view or -snes_view
-pc_gasm_print_subdomains - activates the printing of subdomain indices in PCSetUp()
-pc_gasm_overlap - Sets overlap by which to (automatically) extend local subdomains
-pc_gasm_type [basic,restrict,interpolate,none] - Sets PCGASMType

Notes#

To set options on the solvers for each block append -sub_ to all the KSP, and PC options database keys. For example, -sub_pc_type ilu -sub_pc_factor_levels 1 -sub_ksp_type preonly

To set the options on the solvers separate for each block call PCGASMGetSubKSP() and set the options directly on the resulting KSP object (you can access its PC with KSPGetPC())

References#

**** -*** M Dryja, OB Widlund, An additive variant of the Schwarz alternating method for the case of many subregions Courant Institute, New York University Technical report
**** -*** Barry Smith, Petter Bjorstad, and William Gropp, Domain Decompositions: Parallel Multilevel Methods for Elliptic Partial Differential Equations, Cambridge University Press.