182	1996	Michael Thuné	michael@tdb.uu.se	Partitioning strategies for composite grids

		Abstract

Two different strategies are discussed, for the partitioning of composite
grids, in the context of parallel computers of MIMD type with distributed
memory.  The two strategies are compared theoretically, with respect to
arithmetic load balance and communication overhead. Moreover, the ability
to handle dynamically changing grids is considered.

Composite, structured grids are the natural choice for finite difference
methods on complicated geometries, which can not be covered by a single,
structured grid. A composite grid is a union of (in general curvilinear)
structured grids. So called multi-block grids, frequently used, e.g., in
aerodynamical computations, constitute a special case. The discussion in
the present paper is valid also if the blocks are unstructured, and for
hybrids such as dragon grids.

Composite grids are more complicated to partition than single grids. The
present paper points out the difficulties in detail, giving some
quantification of the overhead that may result from a naive implementation
of composite grid partitioning. These results indicate what are the crucial
implementation issues in the present context.

Keywords: partition, data distribution, composite grid, multi-block, finite
difference, parallel computing