Processor scheduling in distributed-memory systems has received considerable attention in recent years. Several commercial distributed-memory systems use space-sharing processor scheduling. in space-sharing, the set o...
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ISBN:
(纸本)0818684038
Processor scheduling in distributed-memory systems has received considerable attention in recent years. Several commercial distributed-memory systems use space-sharing processor scheduling. in space-sharing, the set of processors in a system is partitioned and each partition is assigned for the exclusive use of a job. Space-sharing policies can be divided into fixed, static, or dynamic categories. For distributed-memory systems, dynamic policies incur high overhead. Thus, static policies are considered as these policies provide a better performance than the fixed policies. Several static policies have been proposed in the literature. In a previously proposed adaptive static policy, the partition size is a function of the number of queued jobs. This policy, however, tends to underutilize the system resources. To improve the performance of this policy, we propose a new policy in which the partition size is a function of the total number of jobs in the system, as opposed to only the queued jobs. The results presented here demonstrate that the new policy performs substantially better than the original policy for the various workload and system parameters. Another major contribution is the evaluation of the performance sensitivity to job structure, variances in inter-arrival times and job service times, and network topology.
The authors examine the issue of robust transaction routing in distributed database systems. A class of dynamic routing strategies which are estimated response times to make routing decisions is studied in details. Si...
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ISBN:
(纸本)0818608935
The authors examine the issue of robust transaction routing in distributed database systems. A class of dynamic routing strategies which are estimated response times to make routing decisions is studied in details. Since response time estimation and decision making depend on the assumed transaction model and parameers, it is important to examine the robustness or sensitivity to the inaccuracy in the assumptions and parameter values. Through simulations, the authors find that the dynamic routing strategy based strictly on response time is too aggressive in sharing loads and makes too many nonpreferred system routings. It is robust with respect to change in the number of database calls per transaction, but is relatively sensitive to the distribution of database calls. Two refinements are proposed which improve system performance as well as robustness of routing decisions.
The paper introduces the concept of collective breakpoints and classifies the possible parallel breakpoints comparing their mechanisms. Based on the collective breakpoints the macrostep-by-macrostep execution mode has...
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ISBN:
(纸本)0769501915
The paper introduces the concept of collective breakpoints and classifies the possible parallel breakpoints comparing their mechanisms. Based on the collective breakpoints the macrostep-by-macrostep execution mode has been defined. After introducing the concept of the execution tree and meta-breakpoints the systematic debugging of message passing parallel programs is explained. The main features and distributed structure of DIWIDE, a macrostep debugger is described. The integration of DIWIDE into the GRADE and WINPAR parallel programming environments is outlined. An algorithm is shown how to generate automatically the collective breakpoints in the GRADE environment.
Algorithms for processing distributed queries require a priori estimates of the size of intermediate relations. Most such algorithms take a “static” approach in which the algorithm is completely determined before pr...
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ISBN:
(纸本)0818620528
Algorithms for processing distributed queries require a priori estimates of the size of intermediate relations. Most such algorithms take a “static” approach in which the algorithm is completely determined before processing begins. If size estimates are found to be inaccurate at some intermediate stage, there is no opportunity to re-schedule, and the result may be far from optimal. Adaptive query execution may be used to alleviate the problem. Care is necessary, though, to ensure that the delay associated with re-scheduling does not exceed the time saved through the use of a more efficient strategy. This paper presents a low overhead delay method to decide when to correct a strategy. Sampling is used to estimate the size of relations, and alternative heuristic strategies prepared in a background mode are used to decide when to correct. Correction is made only if lower overall delay is achieved, including correction time. Evaluation using a model of a distributed data base indicates that the heuristic strategies are near optimal. Moreover, it also suggests that it is usually correct to abort creation of an intermediate relation which is much larger than predicted.
In today's workstation based environment, applications such as design databases, multimedia databases, and knowledge bases do not fit well into the relational data processing framework. The object-oriented data mo...
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ISBN:
(纸本)081864222X
In today's workstation based environment, applications such as design databases, multimedia databases, and knowledge bases do not fit well into the relational data processing framework. The object-oriented data model has been proposed to model and process such complex databases. Due to the nature of the supported applications, object-oriented database systems need efficient mechanisms for the retrieval of complex objects and the navigation along the semantic links among objects. Object clustering and buffering have been suggested as efficient mechanisms for the retrieval of complex objects. However, to improve the efficiency of the aforementioned operations, one has to look at the recent advances in storage technology. This paper is an attempt to investigate the feasibility of using parallel disks for object-oriented databases. It analyzes the conceptual changes needed to map the clustering and buffering schemes proposed in [8,9] on the new underlying architecture. The simulation and performance evaluation of the proposed leveled-clustering and mapping schemes utilizing parallel I/O disks are presented and analyzed.
The design of distributed database has became demanding with the increase in use of IoT and cloud based services. distributed database system's performance is totally relies on its design. Allocation of data is on...
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ISBN:
(纸本)9781665424615
The design of distributed database has became demanding with the increase in use of IoT and cloud based services. distributed database system's performance is totally relies on its design. Allocation of data is one of the major design issues while designing distributeddatabases. This paper presents a new technique for non-redundant allocation of data in distributed database design. The proposed approach allocates the data based on Simplified Biogeography Based Optimization (Simplified-BBO). The performance comparison of Simplified-BBO based approach is done against the GA and BBO based approaches. The proposed approach helps in decreasing the data communication cost during query execution which results in increasing the overall performance of distributed database systems.
Modern database systems-and in particular multidatabase systems, federated database systems and OLAP-oriented data-warehouses-factor the stored data into actual content and meta-data, which structures the available in...
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ISBN:
(纸本)0769512305
Modern database systems-and in particular multidatabase systems, federated database systems and OLAP-oriented data-warehouses-factor the stored data into actual content and meta-data, which structures the available information. This separation is particularly popular in the data-warehousing community, where large amounts of data are structured by and accessible through far smaller amounts of meta-data. Given a parallel or distributed database system, a sophisticated query optimizer requires information on the specific structure of the computing resource, the data distribution, data replication and interconnection bandwidths in order to optimally schedule computational subtasks. Such optimizations are of an even greater importance for next-generation OLAP engines, which attempt to substitute on-demand aggregation into virtual data-cubes and caching for eager preaggregation. Given the demand for ever faster response times and exponentially growing data sets, the parallelization of analytical database systems continuously gains in importance. As a result a portable and comprehensive framework for the representation of optimization-related information becomes necessary. This presentation discusses the possibilities for query optimization in parallel and distributed OLAP systems, given a detailed description of the underlying computing and storage infrastructure. A modeling framework for the description of the computing resource is introduced, which may be applied to a wide array of database systems. A discussion of using profiling information gathered during the execution of queries to dynamically refine the cost estimates given in the meta-data is also provided.
Approximation of partial differential equations of hyperbolic type by a set of ordinary differential equations is presented. The method of weighted-residual is applied. The Galerkin method and the finite element metho...
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ISBN:
(纸本)0780312813
Approximation of partial differential equations of hyperbolic type by a set of ordinary differential equations is presented. The method of weighted-residual is applied. The Galerkin method and the finite element method are presented as examples.
This paper presents a new parallel global routing algorithm for sea-of-gates arrays and its parallel implementation. In the proposed method, making use of the fact that the number of widely distributed nets are compar...
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Many researches have been devoted to designing appropriate concurrency control algorithms for real-time database systems, which not only satisfy consistency requirements but also meet transaction timing constraints as...
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ISBN:
(纸本)0769521320
Many researches have been devoted to designing appropriate concurrency control algorithms for real-time database systems, which not only satisfy consistency requirements but also meet transaction timing constraints as much as possible. Optimistic concurrency control protocols have the nice properties of being non-blocking and deadlock-free, but they have the problems of late conflict detection and transaction restarts. Although the number of transaction restarts is reduced by dynamic adjustment of serialization order (DASO) in real-time database systems, it still has some unnecessary transaction restarts. In this paper, we first propose a new method called dynamic adjustment of execution order (DAEO) and a new optimistic concurrency control algorithm based on DAEO, which can reduce the number of unnecessary restarts near to zero and outperforms the previous algorithms, and then discuss the experiments and the results.
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