Showing papers on "Task (computing) published in 1974"

The Optimal Order of Service in Tandem Queues

Abstract: This paper considers tandem queues for which the order of performing service tasks can be changed, the service times being independent of this order. It determines the optimal order of service when either the service times of different tasks are nonoverlapping or, for two queues in tandem, the service time of one task is constant. For the optimal ordering, the waiting time of every customer is stochastically smaller than for any other.

Data processing system with interrupt functions

Abstract: A data processing system comprises first and second arithmetic units for processing emergent tasks and non-emergent tasks, respectively, a memory for storing the data from the arithmetic units, and a control unit. The control unit selects either an interrupt task or a task being processed in response to the priority levels of the tasks. The first or second arithmetic unit is operated in response to whether a selected task is an emergent task or a non-emergent task.

Communication switching system

Abstract: A communication switching system having distributed control and modular design including a loop structure to which processor modules and storage modules are attached. Input to and output from the loop are effected through line registers, one line register being provided for each communication line. The line registers also function as intermediate storage between sequential processing steps. The processor modules, which are physically separated from the storage modules, are allocated for each step of a task, completely independent of the communication line associated with that task, or any past allocation of that task. Accordingly, messages can be sent by a processor module to any one of the storage modules for fetching or delivering of data and then the data will be routed back to the processor modules. After all required processing has been accomplished, a message will be sent back to the associated line register containing new data, either for output to the line or for later reuse by the system.

Comparison among four psychophysical procedures used in lateralization

Abstract: Psychometrie functions were obtained from two listeners in four psychophysical tasks. The tasks were lateralization procedures in which Os were asked to make discriminations of interaural temporal differences of a 250-Hz tone. The four tasks were: a single-interval yes-no task, a single-interval left-right task, a two-alternative forced-choice task, and a two-interval same-different task. The theory of signal detection provides predictions relating the performances obtained in these four procedures. These predictions could not be verified in this experiment when it was assumed that the Os were listening to changes in lateral position produced by the interaural temporal difference. The data were, however, consistent with the assumption that Os use lateral motion as a cue for detection in two-interval tasks and lateral position as a cue in single-interval tasks.

A general purpose task queueing mechanism for small machines

Abstract: A general purpose mechanism for the queueing of tasks is an important component in an ‘intelligent satellite’ system interfacing a community of users to a range of computing facilities. The queueing mechanism should provide spooling, warm and cold restarts, the ability to pool common resources (e.g. a number of line printers), a means of servicing the queues on a priority basis, and a flexible control mechanism for the system operators. The implementation of such a system for a small (i.e. 16-bit) computer system is described.

Transfer of tracking performance in manual control as a function of plant dynamics

Abstract: This paper considers the transfer of tracking performance in manual control as a function of plant dynamics, where four different plants, i. e., 1/s, 1/s (s+1), 1/s (s+0.1), and 1/s2 are chosen. Using a one-dimensional compensatory tracking system with random function input, the transfer is investigated according to the response patterns, learning curves and indices of transfer.Going from an easy task to the most difficult task (plant 1/s2) yields positive transfer when the two tasks vary little in difficulty, but it does not yield remarkable transfer when the two tasks are widely different in difficulty. Going from a difficult task to the easiest task (plant 1/s) always yields negative transfer regardless of the difference of two tasks.

The utilization of an Information Systems Simulator for line balancing

Abstract: A simulation technique for line-balancing has been developed to utilize an Information Systems Simulator Developed at Lehigh University. A precedence diagram is constructed from the work elements of the line and translated into a partially ordered file. The file system enables the user to determine, store, and maintain pertinent information such as the ultimate followers of each task, the total number of immediately preceding tasks, tasks larger than the desired cycle time, and other information essential for decision-making. The algorithm can process an almost unlimited number of activities and requires less than 30,000 words of core storage. Where perfect balance is impossible, the balancing algorithm can obtain the “best” balance through the use of prescribed station flexibility.

Chapter 2 – processes

Abstract: Publisher Summary This chapter discusses the concurrency in hardware systems. Peripheral devices and their channels work concurrently with the central processing unit. The central processor can also exploit hardware parallelism. A number of machines have increased their computing power by increasing the number of processors. In a hardware system with several arithmetic processors and a number of channels all working simultaneously, organizing the computations associated with these devices is a complex task. To organize them efficiently is even more difficult. One user does not usually exercise the facilities of the system uniformly. User jobs, when executing concurrently, generally should not be aware of each other's existence. It is found that when a job issues a print command, it is not concerned that another job is currently reading in cards. Hardware devices act in a similar fashion. The printer is usually unaware of the reader's presence. To model this adequately, a unit of computation is needed, which reflects this concurrency, namely, the process. Computations do occasionally have to exchange information. To the extent that computations must communicate with each other, they are not completely independent. Processes, which are being used to model computations, must reflect this ability to communicate.

Some experiments in simulating OS/360 from performance data

Abstract: Recent work has indicated that the time a program spends in memory is the primary determinant of the turnaround of the program. We constructed a simulation model of our OS/360 system, using as input performance data gathered by a software monitor, and experimented with differing models of the operating system, program behavior, and hardware configurations to determine an appropriate trade-off between the complexity of models used and the accuracy of the simulation. We constructed a fairly simple model which simulated, from resource requirements of programs, the time a collection of programs resided in memory to within 10% accuracy for the actual completion time of the various programs.The data gathered gave, between any two sample points, the central processor time spent processing on interrupts, on various system tasks, on various problem program tasks and on the large time-sharing task which runs in our system. It also gave the number and total duration of the input-output requests from each task to each device. This data was sampled every time a program was introduced into memory or terminated and left memory.The simulators we constructed had components for the operating system (in various levels of detail), problem program behavior (we tested various distributions of processor burst time and input-output time) and also a component for the input-output configuration (we tested various models of channels and devices with associated queueing). The test of the accuracy of the simulation was how well it compared with the times taken by the actual programs. The results yielded insight into the nature of program behavior as well as how programs interact with the operating system.

Memory and Processor Utilization in Safe States

Abstract: The paper describes tools developed in order to investigate the question whether — if preemption of memory of active tasks is not allowed — a restrictive task activation policy (avoiding any of the active tasks from being blocked for a while due to the memory constraints) reduces the mean processor utilization compared to a more liberal activation policy (implying the risk of blocking active tasks for a while due to memory constraints).