Parallel computing optimization in the Apollo domain network

The performance of parallel computing in a network of Apollo workstations where the processes use the remote procedure call (RPC) mechanism for communication is addressed. The speedup in such systems cannot be accurately estimated without taking into account the relatively large communication overheads. Moreover, it decreases by increasing parallelism when the latter exceeds some certain limit. To estimate the speedup and determine the optimum degree of parallelism, the author characterizes the parallelization and the communication overheads in the system considered. Then, parallel applications are modeled and their execution times are expressed for the general case of nonidentical tasks and workstations. The general case study allows the structural constraints of the applications to be taken into account by permitting their partitioning into heterogeneous tasks. A simple expression of the optimum degree of parallelism is obtained for identical tasks where the inherent constraints are neglected. The fact that the theoretical maximum speedup is bounded by half of the optimum degree of parallelism shows the importance of this measure