Browsing by Subject "Placement"
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Item Open Access Document replication strategies for geographically distributed web search engines(Elsevier Ltd., 2013) Kayaaslan, E.; Cambazoglu, B. B.; Aykanat, CevdetLarge-scale web search engines are composed of multiple data centers that are geographically distant to each other. Typically, a user query is processed in a data center that is geographically close to the origin of the query, over a replica of the entire web index. Compared to a centralized, single-center search engine, this architecture offers lower query response times as the network latencies between the users and data centers are reduced. However, it does not scale well with increasing index sizes and query traffic volumes because queries are evaluated on the entire web index, which has to be replicated and maintained in all data centers. As a remedy to this scalability problem, we propose a document replication framework in which documents are selectively replicated on data centers based on regional user interests. Within this framework, we propose three different document replication strategies, each optimizing a different objective: reducing the potential search quality loss, the average query response time, or the total query workload of the search system. For all three strategies, we consider two alternative types of capacity constraints on index sizes of data centers. Moreover, we investigate the performance impact of query forwarding and result caching. We evaluate our strategies via detailed simulations, using a large query log and a document collection obtained from the Yahoo! web search engine. (C) 2012 Elsevier Ltd. All rights reserved.Item Open Access A novel optimization algorithm for video placement and routing(Institute of Electrical and Electronics Engineers, 2006) Bektaş, T.; Oǧuz, O.; Ouveysi, I.In this paper, we propose a novel optimization algorithm for the solution of the video placement and routing problem based on Lagrangean relaxation and decomposition. The main contribution can be stated as the use of integer programming models to obtain feasible solutions to the problem within the algorithm. Computational experimentation reveals that the use of such integer models help greatly in obtaining good quality solutions in a small amount of solution time.Item Open Access VLSI circuit partitioning for simulation and placement(Bilkent University, 1993-01) Tahboub, RadwanSimulation time of Very Large Scale Integrated (VLSI) circuits may be improved substantially upon the partitioning of the circuit into several smaller sub-circuits. Node Splitting (NS) is the underlying basis for partitioning of large integrated circuits into several, more manageable, and sometimes similar sub-circuits to enhance computer simulation efficiency. In this thesis, a partitioning scheme based on the NS is used to partition VLSI circuits efficiently. The proposed algorithms will be used as a preprocessing step to increase the efficiency of a VLSI analog circuit simulator designed by the EE Department at Bilkent University. With small modifications, the same algorithms are used to form clusters of transistors based on their interconnections. The clustered circuit will then be partitioned using well known heuristics such as Simulated Annealing and Kernighan-Lin to be used in VLSI placement. The results with this method have been superior to those with the conventional implementations. We have observed a factor of 3-4 speed-up in CPU time, together with 5-10% improvement in the cut size. Experimental results show that the proposed algorithms can be efficiently used in VLSI circuit partitioning for simulation and placement.