40082925
Analysis of Packet-Switched Multiple-Bus Multiprocessor Systems
Performance analyses of packet-switched multiple-bus multiprocessor systems are presented. Approximate queuing network models are developed for both synchronous and asynchronous control schemes, and the results are shown to be in good agreement with simulation results. The analysis of the synchronous system is based on a decomposition technique, with each of the shared resources in the system being represented as a single-server queue. For asynchronous systems, the analysis is based on the flow equivalence technique. Numerical results obtained from the analyses indicate that packet-switched multiple-bus multiprocessors with only a few buses perform almost as well as crossbar-based multiprocessors. >
78709
STICS: SCSI-to-IP cache for storage area networks
Abstract Data storage plays an essential role in today's fast-growing data-intensive network services. New standards and products emerge very rapidly for networked data storage. Given the mature Internet infrastructure, the overwhelming preference among the IT community recently is using IP for storage networking because of economy and convenience. iSCSI is one of the most recent standards that allow SCSI protocols to be carried out over IP networks. However, there are many disparities between SCSI and IP in terms of protocols, speeds, bandwidths, data unit sizes, and design considerations that prevent fast and efficient deployment of storage area network (SAN) over IP. This paper introduces SCSI-to-IP cache storage (STICS), a novel storage architecture that couples reliable and high-speed data caching with low-overhead conversion between SCSI and IP protocols. A STICS block consists of one or several storage devices and an intelligent processing unit with CPU and RAM. The storage devices are used to cache and store data while the intelligent processing unit carries out the caching algorithm, protocol conversion, and self-management functions. Through the efficient caching algorithm and localization of certain unnecessary protocol overheads, STICS can significantly improve performance, reliability, and scalability over current iSCSI systems. Furthermore, STICS can be used as a basic plug-and-play building block for data storage over IP. Analogous to “cache memory” invented several decades ago for bridging the speed gap between CPU and memory, STICS is the first-ever “cache storage” for bridging the gap between SCSI and IP making it possible to build an efficient SAN over IP. We have implemented software STICS prototype on Linux operating system. Numerical results using popular benchmarks such as vxbench, IOzone, PostMark, and EMC's trace have shown a dramatic performance gain over the current iSCSI implementation.
229042
Introducing a New Cache Design into Vector Computers
Introduces an innovative cache design for vector computers, called prime-mapped cache. By utilizing the special properties of a Mersenne prime, the new design does not increase the critical path length of a processor, nor does it increase the cache access time as compared to existing cache organizations. The prime-mapped cache minimizes cache miss ratio caused by line interferences that have been shown to be critical for numerical applications by previous investigators. With negligibly additional hardware cost, significant performance gains are obtained by adding the proposed cache memory to an existing vector computer. The performance of the design is studied analytically, using a generic vector computation model. The analytical model is validated through extensive simulation experiments. A performance analysis for various vector access patterns shows that the prime-mapped cache performs significantly better than conventional cache organizations in the vector processing environment. The performance gain will increase with the increase of the speed gap between processors and memories. >
2566279
PRINS: Optimizing Performance of Reliable Internet Storages
Distributed storage systems employ replicas or erasure code to ensure high reliability and availability of data. Such replicas create great amount of network traffic that negatively impacts storage performance, particularly for distributed storage systems that are geographically dispersed over a wide area network (WAN). This paper presents a performance study of our new data replication methodology that minimizes network traffic for data replications. The idea is to replicate the parity of a data block upon each write operation instead of the data block itself. The data block will be recomputed back at the replica storage site upon receiving the parity. We name the new methodology PRINS (Parity Replication in IP-Network Storages). PRINS trades off highspeed computation for communication that is costly and more likely to be the performance bottleneck for distributed storages. By leveraging the parity computation that exists in common storage systems (RAID), our PRINS does not introduce additional overhead but dramatically reduces network traffic. We have implemented PRINS using iSCSI protocol over a TCP/IP network interconnecting a cluster of PCs as storage nodes. We carried out performance measurements on Oracle database, Postgres database, MySQL database, and Ext2 file system using TPC-C, TPC-W, and Micro benchmarks. Performance measurements show up to 2 orders of magnitudes bandwidth savings of PRINS compared to traditional replicas. A queueing network model is developed to further study network performance for large networks. It is shown that PRINS reduces response time of the distributed storage systems dramatically.
11786279
Effects of Arbitration Protocols on the Performance of Multiple-Bus Multiprocessors
36641724
A new and efficient FFT algorithm for distributed memory systems
This paper presents a new and optimal parallel implementation of multidimensional fast Fourier transform algorithm on distributed memory multiprocessors. Its optimality is obtained by minimizing the number of message passings necessary, at the cost of increase in message length. This distinctive feature of the new algorithm effectively utilizes the important architectural property of most of today's distributed memory multiprocessors-wormhole routing for interprocessor communications. By using the algebra of stride permutations and tenser products as a mathematical tool, we are able to derive and formulate an efficient data partition and communication scheme that reduces communication cost from O(N/sup 2/) required for the best known FFT to O(N) on an N/sup 2/-processor machine. Our data partition scheme is natural and efficient for solving discretized boundary value problems such as partial differential equations and finite element analysis. To evaluate the actual performance of our new algorithm in comparison with other existing parallel FFT algorithms, we have carried out implementation experiments on the Intel's Touchstone Delta machine.
2850409
A Framework for Automatic Problem Decomposition in Planning
An intelligent problem solver must be able to decompose a complex problem into simpler parts. A decomposition algorithm would not only be beneficial for traditional subgoal-oriented planning systems but also support distributed, multi-agent planners. In this paper, we present an algorithm for automatic problem decomposition. Given a domain description with a number of objects to be manipulated, our method constructs subspaces complete with subproblem descriptions and operators, and solves the subproblems concurrently. The solutions in individual subspaces are combined using a constraint satisfaction algorithm. The effectiveness of the approach is guaranteed by our careful analysis of the interactions among different subspaces. The results presented in this paper support parallel, distributed and multi-agent planning systems.
10717261
A prediction system for multimedia pre-fetching in Internet
The rapid development of Internet has resulted in more and more multimedia in Web content. However, due to the limitation in the bandwidth and huge size of the multimedia data, users always suffer from long time waiting. On the other hand, if we can predict the web object or page that the user most likely will view next while the user is viewing the current page, and pre-fetch the content, then the perceived network latency can be significantly reduced. In this paper, we present an n-gram based model to utilize path profiles of users from very large web log to predict the users' future requests. Our model is based on a simple extension of existing point-based models for such predictions, but our results show that by sacrificing the applicability somewhat one can gain a great deal in prediction precision. Also we present an efficient method to compress the prediction model size so that it can be fitted into the main memory. Our result can potentially be applied to a wide range of applications on the web, including pro-fetching, enhancement of recommendation systems as well as web caching policies. The experiments based on three realistic web logs have proved the effectiveness of the proposed scheme.
698071
Towards Urban 3D Reconstruction from Video
The paper introduces a data collection system and a processing pipeline for automatic geo-registered 3D reconstruction of urban scenes from video. The system collects multiple video streams, as well as GPS and INS measurements in order to place the reconstructed models in geo- registered coordinates. Besides high quality in terms of both geometry and appearance, we aim at real-time performance. Even though our processing pipeline is currently far from being real-time, we select techniques and we design processing modules that can achieve fast performance on multiple CPUs and GPUs aiming at real-time performance in the near future. We present the main considerations in designing the system and the steps of the processing pipeline. We show results on real video sequences captured by our system.
13952116
Enhancing the Effectiveness of Interactive Case-Based Reasoning with Clustering and Decision Forests
In interactive case-based reasoning, it is important to present a small number of important cases and problem features to the user at one time. This goal is difficult to achieve when large case bases are commonplace in industrial practice. In this paper we present our solution to the problem by highlighting the interactive user- interface component of the CaseAdvisor system. In CaseAdvisor, decision forests are created in real time to help compress a large case base into several small ones. This is done by merging similar cases together through a clustering algorithm. An important side effect of this operation is that it allows up-to-date maintenance operations to be performed for case base management. During the retrieval process, an information-guided subsystem can then generate decision forests based on users' current answers obtained through an interactive process. Possible questions to the user are carefully analyzed through information theory. An important feature of the system is that case-base maintenance and reasoning are integrated in a seamless whole. In this article we present the system architecture, algorithms as well as empirical evaluations.
5926886
Case Mining from Large Databases
This paper presents an approach of case mining to automatically discover case bases from large datasets in order to improve both the speed and the quality of case based reasoning. Case mining constructs a case base from a large raw dataset with an objective to improve the case-base reasoning systems' efficiency and quality. Our approach starts from a raw database of objects with class attributes together with a historical database of past action sequences on these objects. The object databases can be customer records and the historical action logs can be the technical advises given to the customers to solve their problems. Our goal is to discover effective and highly representative problem descriptions associated with solution plans that accomplish their tasks. To maintain efficiency of computation, data mining methods are employed in the process of composing the case base. We motivate the application of the case mining model using a financial application example, and demonstrate the effectiveness of the model using both real and simulated datasets.