Communication processes efficiency factor

The main factors found to be affecting the decision to blowdown manually were the blowdown philosophy, procedures, and training. Factors affecting the efficiency of the decision making process and the execution of blowdown were the ergonomics of the information presentation in the control room communications, and various aspects of the hardware. 

We have used expressions involving the latency, a, and inverse bandwidth, /3, to model the communication time. An alternative model, the Hockney model, is sometimes used for the communication time in a parallel algorithm. The Hockney model expresses the time required to send a message between two processes in terms of the parameters Too and ni, which represent the asymptotic bandwidth and the message length for which half of the asymptotic bandwidth is attained, respectively. Metrics other than the speedup and efficiency are used in parallel computing. One such metric is the Karp-Flatt metric, also referred to as the experimentally determined serial fraction. This metric is intended to be used in addition to the speedup and efficiency, and it is easily computed. The Karp-Flatt metric can provide information on parallel performance characteristics that caimot be obtained from the speedup and efficiency, for instance, whether degrading parallel performance is caused by incomplete parallelization or by other factors such as load imbalance and communication overhead. ... 

Let us consider a performance model for algorithm (c). We first note that, for a manager-worker model in which one process is dedicated to distributing tasks to the others, the maximum efficiency that can be attained with p processes is bounded by [(p — l)/p] x 100%. Other factors that may contribute to lowering the efficiency are load imbalance on the worker processes and communication overhead. 

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