GLB: Lifeline-based Global Load Balancing library in X10

We present GLB, a programming model and an associated implementation that can handle a wide range of irregular paral- lel programming problems running over large-scale distributed systems. GLB is applicable both to problems that are easily load-balanced via static scheduling and to problems that are hard to statically load balance. GLB hides the intricate syn- chronizations (e.g., inter-node communication, initialization and startup, load balancing, termination and result collection) from the users. GLB internally uses a version of the lifeline graph based work-stealing algorithm proposed by Saraswat et al. Users of GLB are simply required to write several pieces of sequential code that comply with the GLB interface. GLB then schedules and orchestrates the parallel execution of the code correctly and efficiently at scale. We have applied GLB to two representative benchmarks: Betweenness Centrality (BC) and Unbalanced Tree Search (UTS). Among them, BC can be statically load-balanced whereas UTS cannot. In either case, GLB scales well-- achieving nearly linear speedup on different computer architectures (Power, Blue Gene/Q, and K) -- up to 16K cores

Three Highly Parallel Computer Architectures and Their Suitability for Three Representative Artificial Intelligence Problems

Virtually all current Artificial Intelligence (AI) applications are designed to run on sequential (von Neumann) computer architectures. As a result, current systems do not scale up. As knowledge is added to these systems, a point is reached where their performance quickly degrades. The performance of a von Neumann machine is limited by the bandwidth between memory and processor (the von Neumann bottleneck). The bottleneck is avoided by distributing the processing power across the memory of the computer. In this scheme the memory becomes the processor (a smart memory ). This paper highlights the relationship between three representative AI application domains, namely knowledge representation, rule-based expert systems, and vision, and their parallel hardware realizations. Three machines, covering a wide range of fundamental properties of parallel processors, namely module granularity, concurrency control, and communication geometry, are reviewed: the Connection Machine (a fine-grained SIMD hypercube), DADO (a medium-grained MIMD/SIMD/MSIMD tree-machine), and the Butterfly (a coarse-grained MIMD Butterflyswitch machine)

Performance Analysis of Universal Robot Control System Using Networked Predictive Control

Networked control systems are feedback control systems with system components distributed at different locations connected through a communication network. Since the communication network is carried out through the internet and there are bandwidth and packet size limitations, network constraints appear. Some of these constraints are time delay and packet loss. These network limitations can degrade the performance and even destabilize the system. To overcome the adverse effect of these communication constraints, various approaches have been developed, among which a representative one is networked predictive control. This approach proposes a controller, which compensates for the network time delay and packet loss actively. This paper aims at implementing a networked predictive control system for controlling a robot arm through a computer network. The network delay is accounted for by a predictor, while the potential of packet loss is mitigated using redundant control packets. The results will show the stability of the system despite a high delay and a considerable packet loss. Additionally, improvements to previous networked predictive control systems will be suggested and an increase in performance can be shown. Lastly, the effects of different system and environment parameters on the control loop will be investigated

Web Workload Generation According to the UniLoG Approach

Generating synthetic loads which are suffciently close to reality represents an important and challenging task in performance and quality-of-service (QoS) evaluations of computer networks and distributed systems. Here, the load to be generated represents sequences of requests at a well-defined service interface within a network node. The paper presents a tool (UniLoG.HTTP) which can be used in a flexible manner to generate realistic and representative server and network loads, in terms of access requests to Web servers as well as creation of typical Web traffic within a communication network. The paper describes the architecture of this load generator, the critical design decisions and solution approaches which allowed us to obtain the desired flexibility

Design of Scalable Java Communication Middleware for Multi-Core Systems

This is a post-peer-review, pre-copyedit version of an article published in The Computer Journal. The final authenticated version is available online at: https://doi.org/10.1093/comjnl/bxs122[Abstract] This paper presents smdev, a shared memory communication middleware for multi-core systems. smdev provides a simple and powerful messaging application program interface that is able to exploit the underlying multi-core architecture replacing inter-process and network-based communications by threads and shared memory transfers. The performance evaluation of smdev on several multi-core systems has shown noticeable improvements compared with other Java shared memory solutions, reaching and even overcoming the performance of natively compiled libraries. Thus, smdev has obtained start-up latencies around 0.76 μs and almost 90 Gbps bandwidth for point-to-point communications, as well as high performance and scalability both for collective operations and representative messaging kernels. This fact has motivated the integration of smdev in F-MPJ, our message-passing implementation in Java.Ministerio de Ciencia e Innovación; TIN2010-1673

NGOS and Internet Use in Uganda

Information technology (IT) research has ignored examining\ud the impact of the Internet on unconnected stakeholder communities in the South. This research, which investigates how non-governmental organisations (NGOs) with connectivity are utilising the Internet for their daily operations, and how they are able to acquire and disseminate information from the Internet to their stakeholders, hopes to correct such injustices. The research was undertaken over an eight-week period in early 1998 in Uganda, East Africa. The survey involved representatives of 33 non-governmental organisations (NGOs) responding to seven openended questions related to their organisations’ use of the Internet, and their information communication patterns. The paper begins with a brief background on Uganda and its telecommunications environment, including a summary of the seven Internet Service Providers (ISPs) currently operating in the country. The survey questions are identified, and the responses are organised into thematic categories which became apparent during the course of the study. The term “Internet” is used to refer to email-only services, as well as World Wide Web services. The research found that NGOs report benefiting from their use of the Internet through reduced transmission costs, access to new and relevant information, and greater contact with their own field sites and partner organisations. NGO representatives’ responses also indicate that the dissemination of Internet-acquired information is occurring with their stakeholders, regardless whether those stakeholders have connectivity or not. The majority of NGOs surveyed (70%) have only one computer with Internet connectivity within their offices; this presents challenges and restrictions in terms of the frequency with which the Internet can be accessed. A mere 5% of the NGOs with field sites reported that those sites were connected with either email or Internet; 33% reported having field sites without any means of direct voice or data transmission systems. The\ud majority of NGOs with World Wide Web service reported using the systems for accessing and researching documents relevant to their work, but 32% of those organisations reported that they either seldom or never used the Internet that was available to them. Most NGOs reported that they used the email to communicate with international partners; use of the\ud Internet for local communications is low. Respondents reported that email was a very convenient mode of communications, effective in transmitting documents at lower costs than other technologies. Obtaining access to the\ud computers, and the sending and receiving of attached documents proved the most problematic issues for respondents; the latter issue raises questions about the quality of training these organisations are receiving\ud from their ISPs. The paper concludes with lessons learned from the research, and recommends areas for more detailed study

Robust adaptive anti-synchronization control of multiple uncertain chaotic systems of different orders

The precise anti-synchronization control of uncertain chaotic systems has always remained an interesting problem. The anti-synchronization control of multiple different orders uncertain chaotic systems increases the complexity and enhances the security of the information signal in secure communications. Hence, it confines the hacking in digital communication systems. This paper proposes a novel adaptive control technique and studies the double combination anti-synchronization of multiple different orders uncertain chaotic systems. The proposed adaptive feedback control technique consists of three fundamental nonlinear components. Each component accomplishes a different objective; (i) stability of the closed-loop, (ii) smooth and fast convergence behaviour of the anti-synchronization error, and (iii) disturbance rejection. The theoretical analysis in (i) to (iii) uses the Lyapunov stability theory. This paper also provides parameters adaptation laws that stabilize the uncertain parameters to some constants. The paper discusses the simulation results of two representative examples of four different orders uncertain chaotic systems. These examples demonstrate anti-synchronization among hyperchaotic Lü, uncertain chaotic Shimizu Morioka, uncertain second-order nonlinear duffing, and uncertain parametrically excited second-order nonlinear pendulum systems. The computer-based simulation results certify the efficiency and performance of the proposed anti-synchronization control approach and compare them with peer works