1426843
Priority based Overlay Multicast with Filtering Mechanism for Distributed Interactive Applications
The "priority-based directed minimum spanning tree" (PST) is designed for distributed interactive applications (DIAs) in which the data are delivered to the receiver node according to their priority; however PST cannot balance the bandwidth usage among the nodes and the system will be unstable when its scale increases. This paper proposes a novel overlay multicast protocol named priority based overlay multicast (POM), which uses the priority, delay and available bandwidth to construct the multicast tree, besides a filtering mechanism is proposed to rebuild the tree when the available bandwidth shortage appears. The effectiveness of our protocol is demonstrated in the simulation results, showing that POM uses the available bandwidth efficiently, besides it keeps the system stable when its scale increases
14850996
Effects of network characteristics on task performance in a desktop CVE system
The influences of network characteristics on the task performance in a desktop collaborative virtual environment (CVE) system were studied. In the experiment, two participants worked together to accomplish a collaborative task and a network emulator was utilized to simulate real network characteristics. The task used in the experiment was designed to be highly interactive and had rigid requirements on network characteristics (e.g. latency and packet loss). The objective performance and subjective assessment were recorded and analyzed quantitatively as a function of network latency and packet loss rate. The experiment results show that network latency has no distinct effect on task performance when network latency is less than 200 ms and lightly affect task performance when network latency is between 200 and 600 ms; packet loss has no effect on task performance when there are 40 state update messages received per second and lightly affect task performance when there are between 15 and 40 state update messages received per second.
11794423
An adaptive consistency maintenance approach for replicated continuous applications
Consistency maintenance is a key problem to replicated continuous applications and dead reckoning (DR) algorithm is widely used in this area. In order to eliminate short-term inconsistency caused by DR algorithm, local-lag approach was proposed. For the purpose of simplicity, fixed lag value is used by local-lag approach and the performance of the approach is greatly deteriorated. In this paper, an adaptive consistency maintenance approach, which is based on local-lag approach, is proposed. The new approach can adjust lag value according to the estimated typical network latency. In order to ensure the criterion of consistency correctness, a lag value adjustment method is also proposed. Through two experiments, the performance of the new approach is evaluated and the results indicate that it is feasible and can greatly improve the performance of the application.
21143930
An I/O Optimal and Scalable Skyline Query Algorithm
Given a set of d-dimensional points, skyline query returns the points that are not dominated by any other point on all dimensions. Currently, BBS (branch-and-bound skyline) is the most efficient skyline processing method over static data in a centralized setting. Although BBS has some desirable features (e.g., I/O optimal and flexibility), it requires large main-memory consumption. In this paper, we present an improved skyline computation algorithm based on best-first nearest neighbor search, called IBBS, which captures the optimal I/O and less memory space (i.e., IBBS visits and stores only those entries that contribute to the final skyline). Its core enables several effective pruning strategies to discard non-qualifying entries. Extensive experimental evaluations show that IBBS outperforms BBS in both scalability and efficiency for most cases, especially in low dimensions.
31293594
Integrating mRNA Decay Information into Co-Regulation Study
Absolute or relative transcript amounts measured through high-throughput technologies (e.g., microarrays) are now commonly used in bioinformatics analysis, such as gene clustering and DNA binding motif finding. However, transcription rates that represent mRNA synthesis may be more relevant in these analyses. Because transcription rates are not equivalent to transcript amounts unless the mRNA degradation rates as well as other factors that affect transcript amount are identical across different genes, the use of transcription rates in bioinformatics analysis may lead to a better description of the relationships among genes and better identification of genomic signals. In this article, we propose to use experimentally measured mRNA decay rates and mRNA transcript amounts to jointly infer transcription rates, and then use the inferred transcription rates in downstream analyses. For gene expression similarity analysis, we find that there tends to be higher correlations among co-regulated genes when transcription-rate-based correlations are used compared to those based on transcript amounts. In the context of identifying DNA binding motifs, using inferred transcription rates leads to more significant findings than those based on transcript amounts. These analyses suggest that the incorporation of mRNA decay rates and the use of the inferred transcription rates can facilitate the study of gene regulations and the reconstruction of transcriptional regulatory networks.
8575175
A User-Friendly Methodology for Automatic Exploration of Compiler Options
This paper introduces a practical methodology for automatic exploring compiler optimization options. The strategy behind this methodology is to provide an intelligent mechanism, in which the compiler will automatically identify optimized combination of compiler options for a given application. The decision made by the compiler is based on user requirements on what aspects of the generated code are the most critical for the compiled application through a specialized user interface. A set of pre-built databases of candidate optimized combinations of compiler options will help the compiler to make the right decision. This methodology will dramatically help users to get rid of the burden of fully understanding the compiler’s inner structure and organization to make the most profitable combination of options. All this work is taken by the compiler and the infrastructure proposed in this paper. This paper presents this methodology and describes its principles and technical mechanisms of the components.
14175949
GATES: a grid-based middleware for processing distributed data streams
Increasingly, a number of applications rely on, or can potentially benefit from, analysis and monitoring of data streams. Moreover, many of these applications involve high volume data streams and require distributed processing of data arising from a distributed set of sources. Thus, we believe that a grid environment is well suited for flexible and adaptive analysis of these streams. This paper reports the design and initial evaluation of a middleware for processing distributed data streams. Our system is referred to as GATES (grid-based adaptive execution on streams). This system is designed to use the existing grid standards and tools to the extent possible. It flexibly achieves the best accuracy that is possible while maintaining the real-time constraint on the analysis. We have developed a self-adaptation algorithm for this purpose. Results from a detailed evaluation of this system demonstrate the benefits of distributed processing, and the effectiveness of our self-adaptation algorithm.
2673173
State Aware Data Dissemination over Structured Overlays
We describe the problem of data dissemination in stream-oriented applications where the required filter is a function of the current state. We call such functions dynamic filters. A state aware data dissemination network (SA-DDN) is proposed to support dynamic filters. Two approaches single-level filtering (SF) and multilevel filter decomposition (MFD) are proposed to facilitate the data dissemination. We show how MFD improves performance over SF. We then describe a realization of SA-DDN on top of an improved bi-directional Chord overlay with a built-in multicast mechanism. An application of stock price monitoring is implemented based on SA-DDN and real life stock quotes are collected to demonstrate the feasibility of our system. Extensive simulations are performed to compare the performance of both approaches and provide insight into the advantages of MFD
3172403
On overlay schemes to support point-in-range queries for scalable grid resource discovery
A resource directory is a critical component of a grid architecture. P2P computing paradigm could address some of the scalability issues that make distributed resource discovery services challenging. Unfortunately, most existing distributed hash table (DHT) based P2P overlays have difficulty in treating attribute range queries that are common in resource discovery lookups. This paper proposes a general framework for range-based resource discovery. In particular, the proposed framework maps tree-structured logical data (i.e., range indexing) onto a DHT-based physical node space (i.e., resource brokers). In this paper, we consider three mapping schemes from the logical space onto the physical space. Each mapping scheme uses a different replication mechanism to reduce range search time and to achieve load balance. We analytically and experimentally compare the performance characteristics (query/update costs and workload distributions) of these schemes and discuss their applicability under different resource discovery service scenarios.