A collaborative multimedia environment (CME) allows users to works remotely on common projects by sharing applications (e.g. CAD tools, text editors, white boards) and simultaneously communicate audiovisually. Several...
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ISBN:
(纸本)9780818675829
A collaborative multimedia environment (CME) allows users to works remotely on common projects by sharing applications (e.g. CAD tools, text editors, white boards) and simultaneously communicate audiovisually. Several dedicated applications (e.g. MBone tools) exist for transmitting video, audio and data between users. Due to the fact that they have been developed for the Internet, which does not provide any quality of service (QoS) guarantee, these applications do not or only partially support specification of QoS requirements by the user. In addition, they all come with different user interfaces. In this paper, we first discuss the problems that we experienced both at the host and network levels when executing a multimedia application and varying its resource requirements. We then present the architectural details of a CME that we have been developing in order to help a user to set up and control a collaborative multimedia session.
Coupling PC-based commodity technology withdistributedcomputing methodologies provides an important advance in the development of single-user dedicated systems. Beowulf is a class of experimental parallel workstatio...
ISBN:
(纸本)9780818675829
Coupling PC-based commodity technology withdistributedcomputing methodologies provides an important advance in the development of single-user dedicated systems. Beowulf is a class of experimental parallel workstations developed to evaluate and characterize the design space of this new operating point in price-performance. A key factor determining the realizable performance under real-world workloads is the means devised for interprocessor communications. A study has been performed to characterize a family of interconnect topologies feasible with low cost mass market network technologies. Behavior sensitivities to packet size and traffic density are determined. Findings are presented which compare more complex segmented topologies to the earlier parallel ``channel bonded'' scheme. It is shown that in many circumstances the more complex topologies perform better, and in some circumstances software routing techniques compare favorably to more expensive hardware switch mechanisms.
Dedicated cluster parallel computers (DCPCs) are emerging as low-cost high performance environments for many important applications in science and engineering. A significant class of applications that perform well on ...
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ISBN:
(纸本)9780818675829
Dedicated cluster parallel computers (DCPCs) are emerging as low-cost high performance environments for many important applications in science and engineering. A significant class of applications that perform well on a DCPC are coarse-grain applications that involve large amounts of file I/O. Current research in parallel file systems for distributed systems is providing a mechanism for adapting these applications to the DCPC environment. We present the parallel Virtual File System (PVFS), a system that provides disk striping across multiple nodes in a distributedparallel computer and file partitioning among tasks in a parallel program. PVFS is unique among similar systems in that it uses a stream-based approach that represents each file access with a single set of request parameters and decouples the number of network messages from details of the file striping and partitioning. PVFS also provides support for efficient collective file accesses and allows overlapping file partitions. We present results of early performance experiments that show PVFS achieves excellent speedups in accessing moderately sized file segments.
Summary form only given. UbiWorld is a concept that ties together the notion of ubiquitous computing (Ubicomp) withthat of using virtual reality for rapid prototyping. the goal is to develop an environment where one ...
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ISBN:
(纸本)9780818675829
Summary form only given. UbiWorld is a concept that ties together the notion of ubiquitous computing (Ubicomp) withthat of using virtual reality for rapid prototyping. the goal is to develop an environment where one can explore Ubicomp-type concepts without having to build real Ubicomp hardware. the basic notion is to extend object models in a virtual world using distributed wide-area heterogeneous computing technology to provide complex networking and processing capabilities to virtual reality objects. Starting withthe CAVE/sup TM/ family of display devices, we integrate tools for the construction of 30 objects into the existing library. then, using these objects as models, we can embed new information technology within them. the plan is then to couple the virtual objects to remote computers via fine-grain heterogenous computing technology to provide Ubicomp behavior and functionality to the modeled objects. We tightly couple the process-defined behavior withthe 30 objects and place these objects into rooms, creating a shared virtual world where users can experiment with using the virtual devices. Each object in the world has its behavior controlled by a program running some place on the network. this behavior could be one that in the real object would be provided by a local computer or by a combination of local computer and network connection to remote processors or databases. these "behavior" processes are able to communicate with each other using a shared protocol (UbiWorldcomm). these object also react and are influenced directly by interactions withthe virtual world and users.
Most current approaches in designing and implementing distributed multimedia (MM) presentational applications have concentrated on the performance of the continuous media file servers in terms of seek-time overhead an...
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ISBN:
(纸本)9780818675829
Most current approaches in designing and implementing distributed multimedia (MM) presentational applications have concentrated on the performance of the continuous media file servers in terms of seek-time overhead and real-time disk scheduling; particularly, the quality of service (QoS) negotiation mechanisms they provide are used in a rather static manner, i.e. these mechanisms are restricted to the evaluation of the capacity of certain system components. In contrast to those approaches, we propose a general QoS negotiation framework that supports the dynamic choice of a configuration of system components to support the QoS requirements of the user of a specific application: we consider different possible system configurations and select an optimal one to provide the appropriate QoS support. We document the design and implementation of a QoS negotiation procedure for distributed MM presentational applications, such as news-on-demand. the negotiation procedure described is an instantiation of the general framework for QoS negotiation. Our proposal differs in many respect withthe negotiation functions provided by existing approaches: (1) the negotiation process uses an optimization approach to find a configuration of system components which supports the user requirements, (2) the negotiation process supports the negotiation of a MM document and not only a single monomedia object, (3) the QoS negotiation takes into account the cost to the user; (4) the negotiation process may be used to support automatic adaptation to react to QoS degradations, without intervention by the user/application.
Local Area MultiProcessors (LAMP) is a network of personal workstations withdistributed shared physical memory provided by high performance technologies such as SCI (Scalable Coherent Interface). LAMP is more tightly...
ISBN:
(纸本)9780818675829
Local Area MultiProcessors (LAMP) is a network of personal workstations withdistributed shared physical memory provided by high performance technologies such as SCI (Scalable Coherent Interface). LAMP is more tightly coupled than the traditional local area networks (LAN) but is more loosely coupled than the bus based multiprocessors. this paper presents a distributed scheduling algorithm which exploits the distributed shared memory in SCI-LAMP to schedule the idle remote processors among the requesting workstations. It considers fairness by allocating remote processing capacity to the requesting workstations based on their priorities according to the decay-usage scheduling approach. the performance of the algorithm in scheduling both sequential and parallel jobs is evaluated by simulation. It is found that the higher priority nodes achieve faster job response times and higher speedups than that of the lower priority nodes. Lower scheduling overhead in SCI-LAMP allows finer granularity of remote processors sharing than in LAN.
distributed shared memory (DSM) alleviates the need to program message passing explicitly on a distributed-memory machine. In order to reduce memory latency, a DSM replicates copies of data. this paper examines severa...
ISBN:
(纸本)9780818675829
distributed shared memory (DSM) alleviates the need to program message passing explicitly on a distributed-memory machine. In order to reduce memory latency, a DSM replicates copies of data. this paper examines several current approaches to controlling thrashing caused by false sharing in a DSM. then it introduces a novel memory consistency protocol, writer-owns, which detects and eliminates false sharing at run time. In iterative computations, where the data is accessed similarly every iteration, the writer-owns protocol can have tremendous benefits because the overhead of eliminating false sharing is only incurred once. Performance results show that the writer-owns protocol is competitive with and often better than existing approaches.
Workstation-based distributedcomputing environments are getting popular in both academic and commercial communities due to the continuing trend of decreasing cost/performance ratio and rapid development of networking...
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ISBN:
(纸本)9780818675829
Workstation-based distributedcomputing environments are getting popular in both academic and commercial communities due to the continuing trend of decreasing cost/performance ratio and rapid development of networking technology. However, the work load on these workstations is usually much lower than their computing capacity, especially withthe ever-increasing computing power of new hardware. As a result, the resources of such workstations are often under-utilized and many of them are frequently idle. A preemptive process migration facility can be provided, in such a distributed system, to dynamically relocate running processes among the component machines. Such relocation can help cope with dynamic fluctuations in loads and service needs, improve the system's fault tolerance, meet real-time scheduling deadlines, or bring a process to a special device. Such a facility, however, is not available in the context of conventional Unix family of operating systems. Most of the work on providing a remote execution facility has been on limited-domain distributed operating systems. this paper presents a process migration subsystem for tolerating process and node failures on a workstation based environment. the design and implementation of the subsystem are also presented.
the information retrieval systems on a wide area distributed network, such as the World-Wide Web(WWW), become popular among the extremely large number of users. the caching proxy has an important role on these systems...
ISBN:
(纸本)9780818675829
the information retrieval systems on a wide area distributed network, such as the World-Wide Web(WWW), become popular among the extremely large number of users. the caching proxy has an important role on these systems for improving their accessibility and serviceability. the caching proxy mechanism is discussed in this paper as follows: First, the role and structure of the caching proxy are explained, and two major problems of existing systems are pointed out. Our solution to overcome these problems is proposed next. Changing a file size, by controlling a quality level of cached multimedia data, is proposed as a measure to overcome one problem. As a solution to the other problem, making a cluster among neighboring caching proxies, using hyperlink information, is proposed. Finally, an improved caching proxy mechanism based upon these ideas is shown.
Data-parallel languages, such as High Performance Fortran, are widely regarded as a promising means for writing portable programs for distributed-memory machines. Novel features of these languages call for the develop...
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Data-parallel languages, such as High Performance Fortran, are widely regarded as a promising means for writing portable programs for distributed-memory machines. Novel features of these languages call for the development of new techniques in both compilers and run-time systems. In this paper, we present an improved algorithm for finding the local memory access sequence in computations involving regular sections of arrays with cyclic(k) distributions. After establishing the fact that regular section indices correspond to elements of an integer lattice, we show how to find a lattice basis that allows for simple and fast enumeration of memory accesses. the complexity of our algorithm is shown to be lower than that of the previous solution for the same problem. In addition, the experimental results demonstrate the efficiency of our method in practice.
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