Browsing by Subject "Pipelining"

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    Pipelined fission for stream programs with dynamic selectivity and partitioned state
    (2014-12) Özsema, Habibe Güldamla
    There is an ever increasing rate of digital information available in the form of online data streams. In many application domains, high throughput processing of such data is a critical requirement for keeping up with the soaring input rates. Data stream processing is a computational paradigm that aims at addressing this challenge by processing data streams in an on-the-fly manner. In this thesis, we study the problem of automatically parallelizing data stream processing applications to improve throughput. The parallelization is automatic in the sense that stream programs are written sequentially by the application developers and are parallelized by the system. We adopt the asynchronous data flow model for our work, where operators often have dynamic selectivity and are stateful. We solve the problem of pipelined fission, in which the original sequential program is parallelized by taking advantage of both pipeline and data parallelism at the same time. Our solution supports partitioned stateful data parallelism with dynamic selectivity and is designed for shared-memory multi-core machines. We first develop a cost-based formulation to express pipelined fission as an optimization problem. The bruteforce solution of this problem takes a very long time for moderately sized stream programs. Accordingly, we develop a heuristic algorithm that can quickly, but approximately, solve this problem. We provide an extensive evaluation studying the performance of our solution, including simulations and experiments with an industrial-strength Data Stream Processing Systems (DSPS). Our results show good scalability for applications that contain sufficient parallelism, closeness to optimal performance for the algorithm.
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    ItemOpen Access
    Pipelined fission for stream programs with dynamic selectivity and partitioned state
    (Academic Press, 2016) Gedik, B.; Özsema, H. G.; Öztürk, Ö.
    There is an ever increasing rate of digital information available in the form of online data streams. In many application domains, high throughput processing of such data is a critical requirement for keeping up with the soaring input rates. Data stream processing is a computational paradigm that aims at addressing this challenge by processing data streams in an on-the-fly manner, in contrast to the more traditional and less efficient store-and-then process approach. In this paper, we study the problem of automatically parallelizing data stream processing applications in order to improve throughput. The parallelization is automatic in the sense that stream programs are written sequentially by the application developers and are parallelized by the system. We adopt the asynchronous data flow model for our work, which is typical in Data Stream Processing Systems (DSPS), where operators often have dynamic selectivity and are stateful. We solve the problem of pipelined fission, in which the original sequential program is parallelized by taking advantage of both pipeline parallelism and data parallelism at the same time. Our pipelined fission solution supports partitioned stateful data parallelism with dynamic selectivity and is designed for shared-memory multi-core machines. We first develop a cost-based formulation that enables us to express pipelined fission as an optimization problem. The bruteforce solution of this problem takes a long time for moderately sized stream programs. Accordingly, we develop a heuristic algorithm that can quickly, but approximately, solve the pipelined fission problem. We provide an extensive evaluation studying the performance of our pipelined fission solution, including simulations as well as experiments with an industrial-strength DSPS. Our results show good scalability for applications that contain sufficient parallelism, as well as close to optimal performance for the heuristic pipelined fission algorithm.
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    ItemOpen Access
    A simulation study on HTTP performance analysis in terms of its interaction with TCP
    (1998) Gürkan, Deniz
    In this thesis, we have performed a. simulation study on performance analysis of HTTP (HyperTrext Transfer Protocol) in terms of its interaction with TCP ('Transmission Control Protocol). The latency through internet connections can he reduced by making modicifations on the application and transport layer protocols. For the simulations, we have built models of HTTP/l.O and HTTP/1.1 using a simulation package Network Simula.- tor. Pour different connection mechanisms have been realized. They are serial, parallel, pipelined and segment-filled connections. Serial and parallel connections are simulated for comparison purposes. These are connection mechanisms of HTTP/I.O. The modification proposed in in HTTP /1.1 is pipelined connection. VVe have obtained segment-filled connection by modifying pipelined case. We have examined the performance of each modification and compared their simulation results with HTTP/I.O connections. For the traffic conditions used in the simulations, segment-filled and pipelined connections performed better in terms of effective web page retrieval rate. In addition, a,s a modification to the TCP, we have increased the initial window size and compared vvith the one segment initial window size case. Changing initial window size' from I l.o 2 and .‘1 has increased the performance of each connection case individually.