| Popis: |
There has been much research interest in efficient implementations of the Committed Choice Non-Deterministic (CCND) logic languages on parallel computers. To take full advantage of the speed gains of parallel computers, methods need to be found to automatically distribute goals over the machine processors, ideally with as little involvement from the user as possible. In this thesis we explore some automatic goal distribution strategies for the execution of the CCND languages on commercially available distributed memory parallel computers. There are two facets to the goal distribution strategies we have chosen to explore: demand driven An idle processor requests work from other processors. We describe two strategies in this class: one in which an idle processor asks only neighbouring processors for spare work, the nearest-neighbour strategy; and one where an idle processor may ask any other processor in the machine for spare work, an all-processors strategy. weights Using a program analysis technique devised by Tick, weights are attached to goals; the weights can be used to order the goals so that they can be executed and distributed out in weighted order, possibly increasing performance. We describe a framework in which to implement and analyse goal distribution strategies, and then go on to describe experiments with demand driven strategies, both with and without weights. The experiments were made using two of our own implementations of Flat Guarded Horn Clauses - an interpreter and a WAM-based system - executing on a MEIKO T800 Transputer Array configured in a 2-D mesh topology. |
