We can also consider block variants of preconditioners for accelerated methods. Block methods are normally feasible if the problem domain is a Cartesian product grid; in that case a natural division in lines (or planes in the 3-dimensional case), can be used for blocking, though incomplete factorizations are not as effective in the 3-dimensional case; see for instance Kettler [134]. In such a blocking scheme for Cartesian product grids, both the size and number of the blocks increases with the overall problem size.

- The idea behind block factorizations
- Approximate inverses
- The special case of block tridiagonality
- Two types of incomplete block factorizations

Mon Nov 20 08:52:54 EST 1995