The design of SAM is not specific to the D0 experiment and carries few assumptions about the underlying mass storage level its ideas are applicable to any sequential data access. During the next several years, the D0 experiment will store a total of about 1 PByte of data, including raw detector data and data processed at various levels. The authors present the Sequential Access Model (SAM), which is the data handling system for D0, one of two primary High Energy Experiments at Fermilab. Over a wide range of parameters the algorithms was found to be superior to both no-load balancing, NLB, and shortest-queue first scheduling, SQF. An algorithm was developed to schedule parallel programs in distributed systems. For Poisson job arrivals and exponentially distributed task service times, analytical solutions and computationally efficient bounds were found for Fork-Join TS-PS and JS-PS job response times. The types of site scheduling studied are TS-PS where tasks of a job are scheduled independently at processor-sharing servers, JS-PS in which tasks of a job are scheduled as a more » single entity at processor-sharing servers, and FCFS where tasks of a job are scheduled independently by order of arrival. The study is divided into two parts: (1) develops analytical solutions for Fork-Join Jobs on uniprocessors and multiprocessors and (2) develops and evaluates via simulation Fork-Join jobs and clusters on distributed systems. Two classes of parallel programs are considered: those without any IPC (called Fork-Join jobs) and those with asynchronous and uniform IPC (called clusters). Scheduling parallel programs under the processor-sharing discipline for uniprocessors, multiprocessors, and distributed systems was studied. This methodology proves effective for studying a number of similar problems, and simulations demonstrate that the method accurately predicts system behavior even for relatively small systems. The analysis of the deterministic model is interesting in its own right.
#Galton watson how to#
=, and then show how to translate results from this model to results for large, but finite, values of n.
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