|-pc_composite_type <type: one of multiplicative, additive, symmetric_multiplicative, special>||- Sets composite preconditioner type|
|-pc_use_amat||- activates PCSetUseAmat()|
|-pc_composite_pcs||- <pc0,pc1,...> list of PCs to compose|
Notes: To use a Krylov method inside the composite preconditioner, set the PCType of one or more inner PCs to be PCKSP. Using a Krylov method inside another Krylov method can be dangerous (you get divergence or the incorrect answer) unless you use KSPFGMRES as the outer Krylov method To use a different operator to construct one of the inner preconditioners first call PCCompositeGetPC(), then call PCSetOperators() on that PC.