An examination is made of heuristic algorithms for processing distributed queries using generalized joins. As this optimization problem is NP-hard, a heuristic algorithm is used to form/formulate strategies to process...
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ISBN:
(纸本)0818608935
An examination is made of heuristic algorithms for processing distributed queries using generalized joins. As this optimization problem is NP-hard, a heuristic algorithm is used to form/formulate strategies to process queries. It has a special property in that its overhead can be controlled. The higher its overhead the better the strategies it produces. Modeling on a testbed of queries demonstrates that there is a tradeoff between the strategy's execution and formulation delays. The modeling results also support the notion that simple greedy heuristic algorithms are sufficient in that they are likely to lead to near-optimal strategies and that increasing the overhead in forming strategies is only marginally beneficial. Both the strategy formulation and execution delays are examined in relation to the number of operations specified by the strategy and the total size of partial results.
In the context of scientific computing, the computational steering consists in the coupling of numerical simulations with 3D visualization systems through the network. This allows scientists to monitor online the inte...
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ISBN:
(纸本)0769526977
In the context of scientific computing, the computational steering consists in the coupling of numerical simulations with 3D visualization systems through the network. This allows scientists to monitor online the inter mediate results of their computations in a more interactive way than the batch mode, and allows them to modify the simulation parameters on-the-fly. While most of existing computational steering environments support parallel simulations, they are often limited to sequential visualization systems. This may lead to an important bottleneck and increased rendering time. To achieve the required performance for online visualization, we have designed the EPSN framework, a computational steering environment that enables to interconnect legacy parallel simulations with parallel visualization systems. For this, we have introduced a redistribution algorithm for unstructured data, that is well adapted to the context of M x N computational steering. Then, we focus on the design of our parallel viewer and present some experimental results obtained with a particle-based simulation in astrophysics.
Split execution is a common model for providing a friendly environment on a foreign machine. In this model, a remotely executing process sends some or all of its system calls back to a home environment for execution. ...
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ISBN:
(纸本)0769507832;0769507840
Split execution is a common model for providing a friendly environment on a foreign machine. In this model, a remotely executing process sends some or all of its system calls back to a home environment for execution. Unfortunately, hand-coding split execution system for experimentation and research is difficult and error-prone. We have built a tool, Bypass, for quickly producing portable and correct split execution systems for unmodified legacy applications. We demonstrate Bypass by using it to transparently connect a POSIX application to a simple data staging system based on the Globus toolkit.
Algorithms for generalized particle methods are discussed in the context of high-performance paralleldistributed computing. An object-oriented framework for such methods is presented along with the implementation of ...
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ISBN:
(纸本)0818681187
Algorithms for generalized particle methods are discussed in the context of high-performance paralleldistributed computing. An object-oriented framework for such methods is presented along with the implementation of several very different scientific particle-based applications using the POET framework.
Efficiently simulating discrete-event models in a parallel and distributed manner is a challenging endeavour On one hand, various factors, such as hardware infrastructure or model characteristics, have to be considere...
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ISBN:
(纸本)0769526977
Efficiently simulating discrete-event models in a parallel and distributed manner is a challenging endeavour On one hand, various factors, such as hardware infrastructure or model characteristics, have to be considered. On the other hand, there is a wide variety of algorithms which address subproblems of parallel and distributed simulation and whose performance depends on the application at hand. We illustrate the resulting difficulties with respect to the development of parallel and distributed simulation systems and argue that the simulation of distributed simulation systems is a feasoble approach to alleviate them. To underpin this, we introduce SIMSIM, a sequential simulator for parallel and distributed simulation systems. SmSim's pertinency is illustrated by the development of a load balancing algorithm for PDEVS. The algorithm's performance is analysed using SIMSIM and the predicted performance is compared to the performance of its implementation in the simulation system JAMES II.
This paper describes an execution time estimating model for nested transactions running on locally distributed database systems (LDDBSs). At first the model of nested transactions and the model of an LDDBS are establi...
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ISBN:
(纸本)0818674601
This paper describes an execution time estimating model for nested transactions running on locally distributed database systems (LDDBSs). At first the model of nested transactions and the model of an LDDBS are established. The performance evaluation model of nested transactions is then built and some calculation and simulation results of the model are analyzed.
In this paper we show the power of sampling techniques in designing efficient distributed algorithms. In particular, we show that using sampling techniques, on some networks, selection can be done in such a way that t...
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ISBN:
(纸本)0818677937
In this paper we show the power of sampling techniques in designing efficient distributed algorithms. In particular, we show that using sampling techniques, on some networks, selection can be done in such a way that the message complexity is independent of the cardinality of the set (file), provided the file size is polynomial in the network size. For example, given a file F of size n and an integer k(1 less than or equal to k less than or equal to n), on a p-processor de Bruijn network, our deterministic selection algorithm can find the kth smallest key from F using O(p log(3) p) messages and with a communication delay of O(log(3) p), and that our randomized selection algorithm can finish the same task using only O(p) messages and a communication delay of O(log p) with high probability, provided the file size is polynomial in network size. Our randomized selection outperforms the existing approaches in terms of both message complexity and communication delay. The property that the number of messages needed and the communication delay are independent of the size of the file makes our distributed selection schemes extremely attractive in such domains as very large database systems. Making use of our selection algorithms to select pivot element(s), we also develop a near optimal quicksort-based sorting scheme and a nearly optimal enumeration sorting scheme for sorting large distributed files on the hypercube and de Bruijn networks. Our algorithms are fully distributed without any a priori central control.
An important development in cluster computing is the availability of multiprocessor workstations. These are able to provide additional computational power to the cluster without increasing network overhead, and allow ...
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ISBN:
(纸本)0818681187
An important development in cluster computing is the availability of multiprocessor workstations. These are able to provide additional computational power to the cluster without increasing network overhead, and allow multiparadigm parallelism, which we define to be the simultaneous application of both distributed and shared memory parallel processing techniques to a single problem. In this paper we compare execution times and speedup of parallel programs written in a pure message-passing paradigm with those that combine message passing and shared-memory primitives in the same application. We consider three basic applications that are common building blocks for many scientific and engineering problems: numerical integration, matrix multiplication and Jacobi iteration. Our results indicate that the added complexity of combining shared- and distributed-memory programming methods in the same program doe snot contribute sufficiently to performance to justify the added programming complexity.
An application programming interface (API) was developed for executing parallel jobs in distributed computer systems. The scheme was implemented through design of an interface which provided dynamic establishment of c...
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ISBN:
(纸本)0769512968
An application programming interface (API) was developed for executing parallel jobs in distributed computer systems. The scheme was implemented through design of an interface which provided dynamic establishment of communication links between processes. Synchronization of the parallel database access was achieved through the fence operation which also allowed scalable initialization of parallel jobs.
Existing parallel programming environments for networks of workstations improve the performance of computationally intensive applications by using message passing or virtual shared memory to alleviate CPU bottlenecks....
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ISBN:
(纸本)0818675829
Existing parallel programming environments for networks of workstations improve the performance of computationally intensive applications by using message passing or virtual shared memory to alleviate CPU bottlenecks. This paper describes an approach based on message passing that addresses both CPU and I/O bottlenecks for a specific class of distributed applications on ATM networks. ATM provides the bandwidth required to utilize multiple I/O channels in parallel. This paper also describes an environment based on distributed process management and centralized application management that implements the approach. The environment adds processes to a running application when necessary to alleviate CPU and I/O bottlenecks, while managing process connections in a manner that is transparent to the application.
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