14112050
Distributed particle simulation method on adaptive collaborative system
Abstract This paper presents a distributed N-body method based on an adaptive collaborative system model. The collaborative system is formed by the distributed objects on a distributed system. The system can be reconfigured during the computation to fully utilize the computing power of the networked hosts. The method is implemented in Java and RMI to support distributed computing in heterogeneous environment. A distributed tree structure is designed for communication-efficient computation of N-body method. The performance test shows satisfactory speedup and portability of the method on both homogeneous and heterogeneous clusters. The collaborative system model can be used in various applications and it is expandable to wide-area environment.
11115305
Graph Scaling: A Technique for Automating Program Construction and Deployment in ClusterGOP
Program development and resource management are critical issues in large-scaled parallel applications and they raise diffculties for the programmers. Automation tools can benefit the programmer by reducing the time and work required for programming, deploying, and managing parallel applications. In our previous work, we have developed a visual tool, VisualGOP, to help visual construction and automatic mapping of parallel programs to execute on the ClusterGOP platform, which provides a graph-oriented model and the environment for running the parallel applications on clusters. In VisualGOP, the programmer needs to manually build the task interaction graph. This may lead to scalability problem for large applications. In this paper, we propose a graph scaling approach that helps the programmer to develop and deploy a large-scale parallel application minimizing the effort of graph construction, task binding and program deployment. The graph scaling algorithms expand or reduce a task graph to match the specified scale of the program and the hardware architecture, e.g., the problem size, the number of processors and interconnection topology, so as to produce an automatic mapping. An example is used to illustrate the proposed approach and how programmer benefits in the automation tools.
14338621
A distributed object model for solving irregularly structured problems on cluster
This paper presents a distributed object model MOIDE (Multithreaded Object-oriented Infrastructure on Distributed Environment) for solving irregularly structured problems on cluster. The primary appeal of MOIDE is its flexible system structure that is adaptive to heterogeneous architecture of a cluster. MOIDE integrates the object-oriented and multithreaded methodologies to set up a unified computing environment. Both the shared-data access and remote messaging are incorporated in a two-layer communication mechanism for efficient inter-object communication with the common communication interface. MOIDE supports dynamic load balancing by its autonomous load scheduling technique. A runtime support system implements the MOIDE model as a platform-independent infrastructure for developing and executing irregularly structured applications. N-body, ray tracing, and conjugate gradient applications are implemented to illustrate the advantages of MOIDE model.
1335499
Dynamic configuration management in a graph-oriented Distributed Programming Environment
Dynamic configuration is a desirable property of a distributed system where dynamic modification and extension to the system and the applications are required. It allows the system configuration to be specified and changed while the system is executing. This paper describes a software platform that facilitates a novel approach to the dynamically configurable programming of parallel and distributed applications and systems. This platform is based on a graph-oriented model and it provides support for constructing reconfigurable distributed programs. We describe the design and implementation of a dynamic configuration manager for the graph-oriented distributed programming environment. The requirements and services for dynamic reconfiguration are identified. The architectural design of a dynamic configuration manager is presented, and a parallel virtual machine-based prototypical implementation of the manager, on a local area network of workstations, is described.
47269670
Motion estimation for content adaptive video compression
A multistage motion estimation scheme is proposed. The scheme extracts video characteristics by first performing an online video analysis separately for foreground and background regions. Motion parameters are extracted and passed to the next stage. The next stage includes a mathematical model for the block distortion surface (BDS) that enables the algorithm to accordingly adjust its search technique. The search is performed on a precise search area adaptive to the statistical property of the motion vector prediction error. Due to its self-tuning property, not only does the proposed scheme adapt to scenes by yielding better visual quality but it also yields a lower computational complexity, compared with the other predictive motion estimation algorithms on standard benchmark sequences
17387040
Automated judgment of document qualities
The authors report on a series of experiments to automate the assessment of document qualities such as depth and objectivity. The primary purpose is to develop a quality-sensitive functionality, orthogonal to relevance, to select documents for an interactive question-answering system. The study consisted of two stages. In the classifier construction stage, nine document qualities deemed important by information professionals were identified and classifiers were developed to predict their values. In the confirmative evaluation stage, the performance of the developed methods was checked using a different document collection. The quality prediction methods worked well in the second stage. The results strongly suggest that the best way to predict document qualities automatically is to construct classifiers on a person-by-person basis.
16353382
Determining the size of spatial clusters in focused tests: Comparing two methods by means of simulation in a GIS
Abstract. Based on a four-point evaluation system consisting of accuracy, consistency, power, and chance to commit type I errors, this study compares Tango's minimum p (MinP) and Stone's maximum relative risk (MaxRR) methods for detecting focused cluster size through simulations in GIS. It reveals that the MinP method is more effective than the MaxRR method. The MinP method exhibits higher levels of accuracy and consistency; and its power and chance to commit type I errors are similar to the MinP method. The MaxRR method has a tendency to underestimate the cluster size, while the MinP method tends to overestimate the cluster size, particularly when the clusters are relatively big and have high relative risk levels. In addition, the MinP method seems to be most effective in revealing the size of clusters when clusters are neither too strong nor too weak. The lowest detection rates for clustering occur when the clustering signal is relatively weak, which is easily understandable. In practice, it might be useful to use both the methods to estimate a range of possible cluster sizes, where the MaxRR method indicates the lower estimate, while the MinP method gives the higher estimate of the cluster size.
9615760
Asynchronous rate control for multi-object videos
Object-based coding can potentially achieve a higher degree of compression and better visual quality. The objects in a scene are not always synchronous, that is, they have different temporal resolutions. In some applications, it is more efficient to transmit asynchronous objects with different temporal rates so as to achieve a better tradeoff between temporal and spatial resolutions. This requires to balance the qualities of individual objects while ensuring an overall visual quality with a given bit rate. This paper proposes a rate control algorithm for multiple video object encoding, which is suitable for both synchronous and asynchronous transmissions. The algorithm aims to maximize scene quality with an accurate bit rate, while efficiently handling buffer fullness. Using an efficient bit allocation strategy, the algorithm achieves accurate target bit rates, provides good coding quality, and decreases buffer overflow/underflow. The proposed algorithm also allows flexible priority adjustment among multiple objects to ensure overall better visual perception. Designed primarily for asynchronous objects, the algorithm treats the synchronous objects as a special case. Experimental results demonstrate that, when giving suitable asynchronous video object planes rates, the proposed algorithm achieves good temporal-spatial tradeoff while yielding accurate rate regulation and effective buffer control.
61852216
Cross-Evaluation: A new model for information system evaluation
In this article, we introduce a new information system evaluation method and report on its application to a collaborative information seeking system, AntWorld. The key innovation of the new method is to use precisely the same group of users who work with the system as judges, a system we call Cross-Evaluation. In the new method, we also propose to assess the system at the level of task completion. The obvious potential limitation of this method is that individuals may be inclined to think more highly of the materials that they themselves have found and are almost certain to think more highly of their own work product than they do of the products built by others. The keys to neutralizing this problem are careful design and a corresponding analytical model based on analysis of variance. We model the several measures of task completion with a linear model of five effects, describing the users who interact with the system, the system used to finish the task, the task itself, the behavior of individuals as judges, and the self-judgment bias. Our analytical method successfully isolates the effect of each variable. This approach provides a successful model to make concrete the “three-realities” paradigm, which calls for “real tasks,” “real users,” and “real systems.” © 2006 Wiley Periodicals, Inc.