32609589
Avoiding checkpoint contamination in parallel systems
Checkpointing and rollback recovery is a very effective technique to tolerate faults, provided the application is able to recover from a previous checkpoint and proceed with a failure-free computation. However, this technique may fall short if the checkpoint files are somehow contaminated by errors. This paper presents two mechanisms that may be used to determine if a committed checkpoint is error-free or not. These techniques can be used simultaneously for error detection and failure recovery. Both of them are based on checkpoint duplication: one makes use of spatial redundancy while the other is based on temporal redundancy. We discuss the main problems and trade-offs that have to be dealt with to implement these techniques. We then present a performance study that clearly shows the pros and cons of each one. As far as we know, this paper presents the first implementation of these mechanisms in a standard parallel computing system.
12469936
JAMES: A Platform of Mobile Agents for the Management of Telecommunication Networks
This paper presents an overview of JAMES, a Java-based platform of mobile agents that is mainly oriented for the management of data and telecommunication networks. This platform has been developed on behalf of a Eureka Project (Σ!1921) and the project partners are Siemens SA, University of Coimbra and Siemens AG. We describe the main architecture of the platform giving more emphasis to the most important features. To show the effectiveness of some of the techniques that have been implemented we will present some performance results that compare the JAMES platform with the Aglets Workbench. 
 
The main target of our platform is network management and telecommunication applications. In this line, we have done a Java-based implementation of SNMP that has been integrated within the platform. The industrial partners of our project (i.e. Siemens S.A.) have developed a prototype application for TMN performance management. Although it is still a prototype it is being used to validate the technological advantages of using mobile agents in the management of telecommunication networks.
30244538
Fault-tolerance on regular decomposition grid applications
Writing parallel applications is considerably more complex due to additional problems not found in the sequential environment. The main problems include communication, synchronization data partitioning and distribution, mapping of processes, heterogeneity and fault tolerance. Fault tolerance is a very important feature in parallel/distributed systems since the mean time between failures of the system decreases with the number of processors, and the failure of just one process(or) can lead to the crash of the entire application. This paper presents an example of a parallel library (PUL-RD) that solves most of the problems pointed out before and provides support for fault tolerance. The original version of the library offers high-level support for parallelism in a portable way and can be used to write grid-based parallel applications which have a regular decomposition. In this paper, we will describe the fault-tolerance issues that were incorporated into the PUL-RD, giving special attention to the functionality of the checkpointing scheme.<<ETX>>
9570610
Towards Manageable Mobile Agent Infrastructures
This paper addresses the problem of managing distributed mobile agent infrastructures. First, the weaknesses of current mobile agent implementations will be discussed and identified from the manageability viewpoint. The solutions devised and experimented in order to alleviate these weaknesses in our own agent platform will then be presented. These solutions are generic and could easily be applied to the majority of existing mobile agent implementations. The paper will finish with the discussion of a new approach we are following in the M&M Project, based on a rather different architecture that significantly reduces the manageability requirements.
11507520
Web-based Metacomputing with JET
7711926
A flexible mobile-agent framework for accessing information systems in disconnected computing environments
Over the last few years, the importance of mobile computing has been steadily increasing. While it is important to provide support for accessing databases in disconnected computing environments, many of the information systems being deployed today are using a three-tier architecture. It is becoming vital to find ways of providing reliable access to the business logic present in the middle-tier for mobile applications. The authors present a component based framework that enables client applications to send mobile agents to interact with application servers in disconnected computing environments. This framework allows the applications to benefit from the advantages of using mobile agents in disconnected computing environments, and at the same time provides integration between mobile clients and corporate information systems.
10991338
Variation-Aware, Library Compatible Delay Modeling Strategy
Variability in digital integrated circuits makes timing verification an increasingly challenging task. Statistical static timing analysis has been proposed as a solution to this problem, but most of the work has concentrated in the development of timing engines for computing delay propagation. Such tools rely on the availability of delay formulas accounting for both cell and interconnect delay. In this paper, we concentrate on the impact of interconnect on delay and propose an extension to the standard modeling strategies that is variation-aware and compatible with such statistical engines. Our approach, based on a specific type of perturbation analysis, allows for the analytical computation of the quantities needed for statistical delay propagation. We also show how perturbation analysis can be performed when only the standard delay table lookup models are available for the standard cells. Results from applying our proposed modeling strategy to computing delays and slews in several instances accurately match similar results obtained using electrical level simulation
9436195
Satisfiability models and algorithms for circuit delay computation
The existence of false paths represents a significant and computationally complex problem in the estimation of the true delay of combinational and sequential circuits. In this article we conduct a comprehensive study of modeling circuit delay computation, accounting for false paths, as a sequence of instances of Boolean satisfiability. Several path sensitization models and delay models are studied. In addition we evaluate some of the most competitive Boolean satisfiability algorithms seeking to identify which are best suited for solving circuit delay computation problems. Finally, realistic delay modeling (taking into account extracted interconnect delays and fanout data) is considered in order to experimentally evaluate the complexity of solving real-world instances.
528194
Algorithms for solving Boolean satisfiability in combinational circuits
Boolean satisfiability is a ubiquitous modeling tool in Electronic Design Automation (EDA). It finds application in test pattern generation, delay-fault testing, combinational equivalence checking and circuit delay computation, among many other problems. Moreover Boolean satisfiability is in the core of algorithms for solving binate covering problems. This paper describes how Boolean satisfiability algorithms can take circuit structure into account when solving instances derived from combinational circuits. Potential advantages include smaller run times, the utilization of circuit-specific search pruning techniques, avoiding the overspecification problem that characterizes Boolean satisfiability testers, and reducing the time for iteratively generating instances of SAT from circuits. The experimental results obtained on several benchmark examples in two different problem domains display dramatic reductions in the run times of the algorithms, and provide clear evidence that computed solutions can have significantly less specified variable assignments than those obtained with common SAT algorithms.
15163719
Solving satisfiability in combinational circuits
As EDA evolves, researchers continue to find modeling tools to solve problems of test generation, design verification, logic, and physical synthesis, among others. One such modeling tool is Boolean satisfiability (SAT), which has very broad applicability in EDA. The authors review modern SAT algorithms, show how these algorithms can account for structural information in combinational circuits, and explain what recursive learning can add to SAT.
14564941
PetroGrapher: managing petrographic data and knowledge using an intelligent database application
This paper describes the PetroGrapher system, an intelligent database application to support petrographic analysis, interpretation of oil reservoir rocks, and management of relevant data using resources from both knowledge-based system technology and database technology. In this project, the visual tacit knowledge applied in petrographic analysis was rendered explicit through the collection of cases (rock descriptions), which were then used in the development of a domain ontology organized in a partonomy. Expert-level basic features, which we call ‘visual chunks’, were identified. The cases were further compared against the ontology to elucidate the relations between features in descriptions of rocks, visual chunks and expert interpretations. The domain knowledge was represented through a set of frames and knowledge graphs. The knowledge graphs are applied to recognize the visual chunks in the user data and retrieved the related interpretation. The system was developed as a structure tightly coupled with a relational database system, which acts as a repository for the knowledge base and the user data, and an object-oriented component, which preserves the semantics of data and develops inferences. The system was validated by three groups of users with different levels of expertise. q 2003 Elsevier Ltd. All rights reserved.