TWO time-sharing models are described. One is the conventional round-robin model in which each customer receives at most q seconds of service at a time. If this completes his service requirement, he leaves the system; otherwise he joins the end of the queue to await his next turn. The second model is a modification of the round-robin system in which the amount of service per pass depends on the rate at which programs arrive in the system. The models are analyzed under the assumption of constant, nonzero overhead when the processor swaps one program for another. Expressions are derived for the mean waiting time in queue as a function of service requirement and for the mean system cost due to waiting time in queue.
Abstract.The multi-level time sharing algorithm is studied. Each new job joins the bottom level queue. After each quantum of service it goes to the next higher level until it has completed service. The server always selects the lob at the head of the lowest level nonempty queue. A constant overhead is incurred for each qua~atum of service. Mean waiting time and mean system delay cost are better than those of the round robin model. Description of Model.The multiple-level (ML) system consists of a (possibly infinite) number of levels, each with its own queue. A program entering the system joins the queue at the lowest level and awaits its turn for service. If it does not finish during its allotted quantum service, it is fed back to the queue at the next higher level. At the end of a quantum service, the next program served will be the one at the head of the lowest-level non-empty queue. In the case of a finite number of levels, a program requiring service at the highest level receives a quantum at a time (with associated swap) without feedback to the end of the queue.The multiple-level model has been studied by Coffman and Kleinrock [1] for single-quantum allocation and zero overhead, with a constant quantum size at all levels. Schrage [2] has also investigated this system with different quantum sizes for the various levels. Adiri [3] and Coffman and Kleinrock [1] have studied a modification of the multiple-level system wherein the level at which a program enters the system is determined by an externally-assigned priority. Adiri also allows different quantum sizes for the various levels.Time is continuous, so that a program leaves the system as soon as its service requirement is completed. We assume a constant quantum size, q, and a constant, non-negative swap time, s. The swap is assumed to occur at the beginning of a quantum service.
The Requirements and Development Language (RDL) ;,~ a non-procedural language which permits the user to describe all aspects of software development, from requirements specification through maintenance.nuL statements are used, incrcmentally, to build an integrated data base containing all data pertinent to the project. From this data base, standard reports can be generated to analyze requirements or design specification, to track problem areas, to produce documentation, to furnish up-to-date status information, and to ensure communication and coordination among all phases of the development process. RDL was developed, and is being used, as an internal tool for Sperry Univac Software Development.
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