7929531
Closed-Form Deterministic End-to-End Performance Bounds for the Generalized Processor Sharing Scheduling Discipline
The Generalized Processor Sharing (GPS) schedulingdiscipline is an important scheduling mechanism that can support both class isolation and bandwidth sharing among different service classes, thus making itan appealing choice for networks providing multiple services with Quality-of-Service guarantees. In this paper, we study a broad classof GPS networks known as Consistent Relative Session Treatment}(CRST) GPS networks and establish closed-form end-to-end performance boundsfor CRST GPS networks. This result generalizes the results of Parekhand Gallager (1994) where simple, closed-form end-to-end performancebounds are derived for a special sub-class of CRST GPS networks, theso-called Rate Proportional Processor Sharing (RPPS) GPS networks, but performance bounds for the general CRST GPS networks do not haveclosed-form. Our result is obtained through the notion of CRSTpartition, which in fact yields a broader class of CRST GPS networksthan the one originally defined in (Parekh and Gallager, 1993). Moreover,our approach is quite general. It not only applies to the deterministicanalysis of GPS networks, but can also be employed in the study of GPSnetworks in a stochastic setting.
17231470
Dynamic scheduling of parallel computations
Structures of parallel programs are usually represented by task graphs in the scheduling literature. Such graphs are sometimes obtained at compile time. In many other cases, however, they can be determined only at run time. In this paper, we consider the scheduling of parallel computations whose task graphs are generated at run time. We analyze the case where the task graph is a random out-tree. When the number of offspring of a task has a geometric distribution whose parameter is decreasing and convex in the level, then the breadth-first policy stochastically minimizes the makespan. If, however, this parameter is increasing and concave, then the depth-first policy stochastically minimizes the makespan.
15724338
Stochastic Scheduling with Variable Profile and Precedence Constraints
In this paper, we consider the stochastic profile scheduling problem of a partially ordered set of tasks on uniform processors. The set of available processors varies in time. The running times of the tasks are independent random variables with exponential distributions. We obtain a sufficient condition under which a list policy stochastically minimizes the makespan within the class of preemptive policies. This result allows us to obtain a simple optimal policy when the partial order is an interval order, an in-forest, or an out-forest.
774892
Single Machine Scheduling Subject To Precedence Delays
Abstract A single-machine scheduling problem with precedence delays is analyzed. A set of n tasks is to be scheduled on the machine in such a way that the makespan is minimized. The executions of the tasks are constrained by precedence delays, i.e., a task can start its execution only after any of its predecessors has completed and the delay between the two tasks has elapsed. In the case of unit execution times and integer lengths of delays, the problem is shown to be NP-hard in the strong sense. In the case of integer execution times and unit length of delays, the problem is polynomial, and an O(n2) optimal algorithm is provided. Both preemptive and non-preemptive cases are considered.
6592348
Scheduling UET-UCT Series-Parallel Graphs on Two Processors
Abstract The scheduling of task graphs on two identical processors is considered. It is assumed that tasks have unit-execution-time, and arcs are associated with unit-communication-time delays. The problem is to assign the tasks to the two processors and schedule their execution in order to minimize the makespan. A quadratic algorithm is proposed to compute an optimal schedule for a class of series-parallel graphs, called SP1 graphs, which includes in particular in-forests and out-forests.
252821
Performance Analysis of Stochastic Timed Petri Nets Using Linear Programming Approach
Stochastic timed Petri nets are a useful tool in the performance analysis of concurrent systems such as parallel computers, communication networks and flexible manufacturing systems. In general, performance measures of stochastic timed Petri nets are difficult to obtain for practical problems due to their sizes. In this paper, we provide a method to efficiently compute upper and lower bounds for the throughputs and mean token numbers for a large class of stochastic timed Petri nets. Our approach is based on uniformization technique and linear programming.
3730862
Distributed Resource Allocation in Stream Processing Systems
Distributed stream processing architecture has emerged as appealing solution to coping with the analysis of large amount of data from dispersed sources. A fundamental problem in such stream processing systems is how to best utilize the available resources so that the overall system performance is optimized. We consider a distributed stream processing system that consists of a network of cooperating servers, collectively providing processing services for multiple data streams. Each stream is required to complete a series of operations on various servers. We assume all servers have finite computing resources and all communication links have finite available bandwidth. The problem is to find distributed schemes to allocate the limited computing resources as well as the communication bandwidth in the system so as to achieve a maximum concurrent throughput for all output streams. We present a generalized multicommodity flow model for the above problem. We develop a distributed resource allocation algorithm that guarantees the optimality. We also provide detailed analysis on the complexity of the algorithm and demonstrate the performance using numerical experiments.
2945218
On querying geospatial and georeferenced metadata resources in G-Portal
G-Portal is a Web portal system providing a range of digital library services to access geospatial and georeferenced resources on the Web. Among them are the storage and query subsystems that provide a central repository of metadata resources organized under different projects. In G-Portal, all metadata resources are represented in XML (Extensible Markup Language) and they are compliant to some resource schemas defined by their creators. The resource schemas are extended versions of a basic resource schema making it easy to accommodate all kinds of metadata resources while maintaining the portability of resource data. To support queries over the geospatial and georeferenced metadata resources, a XQuery-like query language known as RQL (Resource Query Language) has been designed. We present the RQL language features and provide some experimental findings about the storage design and query evaluation strategies for RQL, queries.
17450841
An information concierge for the Web
WWW Information Collection, Collaging and Programming (WICCAP) system is a software system for the generation of logical views of web resources, and the extraction of desired information in the form of a structured document. It is designed to enable people to obtain information of interests in a simple and effective manner as well as to make information from the WWW accessible to applications so as to afford automation, inter-operation and Web-awareness among services. A key factor in making this system useful in practice is that it provides tools to automate and facilitate the process of constructing logical representation of websites, to identify and define information of interest, and to retrieving them. In this paper we present the design of the WICCAP system and its two main components, namely Mapping Wizard and Network Extraction Agent.
12952126
Long range dependence and heavy tail distributions
11845096
Integration of audio and visual information for content-based video segmentation
A video sequence usually consists of separate scenes, and each scene includes many shots. For video understanding purposes, it is most important to detect scene breaks. To analyze the content of each scene, detection of shot breaks is also required. Usually, a scene break is associated with a simultaneous change of image, motion, and audio characteristics, while a shot break is only accompanied with changes in image or motion or both. We propose to use audio information along with image and motion information to accomplish segmentation at different levels. Promising results have been obtained with videos digitized from TV programs.