Manager-worker model

Receive work request from a worker If (task index ntask) 

Send next task from list to worker task index = task index + 1 Else 

Send request for new task to manager Receive task or finished from manager While (Ifinished) 

Outline of a dynamic manager-worker task distribution scheme. The number of tasks and processes are designated ntask and p, respectively. One process is assigned to be the manager, and the remaining p — 1 processes are the workers. 

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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. 

In summary, we have here analyzed the performance of a dynamic manager-worker model for disfribufing shell pairs in the parallel computation of fwo-elecfron infegrals. The analysis clearly demonsfrafes fhat the dynamic distribution of shell pairs provides significanfly higher parallel efficiency than the static shell pair distribution, except for very small process counts, and that dynamic load balancing enables utilization of a large number of processes with little loss of efficiency... 

Processes request tasks (atom quartets) by calling the function get quartet, which has been implemented in both a dynamic and a static version. The dynamic work distribution uses a manager-worker model with a manager process dedicated to distributing tasks to the other processes, whereas the static version employs a round-robin distribution of tasks. When the number of processes is small, fhe sfafic scheme achieves the best parallel performance because the dynamic scheme, when run on p processes, uses only p - 1 processes for compulation. As the number of processes increases, however, the parallel performance for the dynamic task distribution surpasses that of the static scheme, whose efficiency is reduced by load imbalance. Wifh fhe entire Fock and density matrix available to every process, no communication is required during the computation of the Fock matrix other than the fetching of tasks in the dynamic scheme. After all ABCD tasks have been processed, a global summation is required to add the contributions to the Fock matrix from all processes and send the result to every process. 

Considerable attention has been focused on the kind of motives which drive the decisions and choices of individuals in a work setting. An influential model of motivation was the "scientific management" movement of F. W. Taylor (1911) which viewed motivation largely in terms of rational individual decisions to maximize financial gain. This theory claimed that workers only wanted to make as much as possible for as little effort as possible, and that they were neither interested in, nor capable of planning and decision- making. 

James Reason offered another useful model, often referred to as the Swiss cheese model, that explains how the many factors can converge, resulting in an incident (Figure 6-5). A company tries to promote safety and prevent catastrophic incidents hy putting into place layers of system defenses, depicted in Figure 6-5 as slices of Swiss cheese. Essentially, the term system defenses refers to the safety-related decisions and actions of the entire company top management, the line supervisors, and the workers. This model recognizes that each defense layer has weaknesses or holes. 

It is clear that legislation alone will not prevent substance abuse. Education is an essential complement and all health care workers should play their r51e in individual or group education. They should also be good role models. Health professionals have easy access to drugs and they must be very careful that they do not fall temptation to the misuse of psychoactive products to alleviate their mood, prevent tiredness, and to combat other stress related symptoms. They should manage their patients along the same lines. 

An example of a model of behavioural preferences that many managers will be familiar with is Belbin s classlflcation of team roles, for example chairman, resource Investigator, company worker, plant, finisher (Belbin, 1981). Measuring people s preferences for team roles has become part of the normal routine of team building. Successful teams need a balance of roles, which in turn means that a balance of preferences needs to exist among the team members. If it does not exist and the team is to function effectively, some members may need to engage in styles of behaviour that do not come naturally. 

Occupational safety management concentrates on the safety of individual workers by promoting their safety-mindedness the prevailing view of human error is that of the traditional safety model where safety control is handled by motivation, and punishment, (for lack of attention). 

Improvements in the analysis of worker risk have resulted from an increased focus on worker activities and the adoption of more general methods for analyzing the effects of human error. For a number of reasons discussed in the NRC report Risk Assessment and Management at Deseret Chemical Depot and the Tooele Chemical Agent Disposal Facility (NRC, 1997), very little modeling of human performance was done in the 1996 QRA for TOCDF. For ex-... 

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