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OptorSim - A Grid Simulator for Studying Dynamic Data Replication Strategies
- International Journal of High Performance Computing Applications
, 2003
"... Abstract Computational Grids process large, computationally intensive prob-lems on small data sets. In contrast, Data Grids process large computational problems that in turn require evaluating, mining and producinglarge amounts of data. Replication, creating geographically disparate identical copies ..."
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Cited by 99 (4 self)
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Abstract Computational Grids process large, computationally intensive prob-lems on small data sets. In contrast, Data Grids process large computational problems that in turn require evaluating, mining and producinglarge amounts of data. Replication, creating geographically disparate identical copies of data, is regarded as one of the major optimisationtechniques for reducing data access costs. In this paper, several replication algorithms are discussed. Thesealgorithms were studied using the Grid simulator: OptorSim. OptorSim provides a modular framework within which optimisation strate-gies can be studied under different Grid configurations. The goal is to explore the stability and transient behaviour of selected optimisationtechniques. We detail the design and implementation of OptorSim andanalyse various replication algorithms based on different Grid workloads. 1 Introduction Within the Grid community much work has been done on providing the basic infrastructure for a typical Grid environment. Globus [3], Condor [1] and recently the EU DataGrid [2] have contributed substantially to core Grid
EFFICIENT ALGORITHMS FOR CLAUSE-LEARNING SAT SOLVERS
, 2004
"... Boolean satisfiability (SAT) is NP-complete. No known algorithm for SAT is of polynomial time complexity. Yet, many of the SAT instances generated as a means of solving real-world electronic design automation problems are simple enough, structurally, that modern solvers can decide them efficiently. ..."
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Cited by 73 (0 self)
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Boolean satisfiability (SAT) is NP-complete. No known algorithm for SAT is of polynomial time complexity. Yet, many of the SAT instances generated as a means of solving real-world electronic design automation problems are simple enough, structurally, that modern solvers can decide them efficiently. Consequently, SAT solvers are widely used in industry for logic verification. The most robust solver algorithms are poorly understood and only vaguely described in the literature of the field. We refine these algorithms, and present them clearly. We introduce several new techniques for Boolean constraint propagation that substantially improve solver efficiency. We explain why literal count decision strategies succeed, and on that basis, we introduce a new decision strategy that outperforms the state of the art. The culmination of this work is the most powerful SAT solver publically available.
Saturation: an efficient iteration strategy for symbolic state space generation
- PROC. TOOLS AND ALGORITHMS FOR THE CONSTRUCTION AND ANALYSIS OF SYSTEMS (TACAS), LNCS 2031
, 2001
"... We present a novel algorithm for generating state spaces of asynchronous systems using Multi–valued Decision Diagrams. In contrast to related work, we encode the next–state function of a system not as a single Boolean function, but as cross–products of integer functions. This permits the applicati ..."
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Cited by 64 (32 self)
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We present a novel algorithm for generating state spaces of asynchronous systems using Multi–valued Decision Diagrams. In contrast to related work, we encode the next–state function of a system not as a single Boolean function, but as cross–products of integer functions. This permits the application of various iteration strategies to build a system’s state space. In particular, we introduce a new elegant strategy, called saturation, and implement it in the tool SMART. On top of usually performing several orders of magnitude faster than existing BDD–based state–space generators, our algorithm’s required peak memory is often close to the final memory needed for storing the overall state space.
The PROSPER Toolkit
, 2000
"... The Prosper (Proof and Specification Assisted Design Environments) project advocates the use of toolkits which allow existing verification tools to be adapted to a more flexible format so that they may be treated as components. A system incorporating such tools becomes another component that can be ..."
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Cited by 45 (2 self)
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The Prosper (Proof and Specification Assisted Design Environments) project advocates the use of toolkits which allow existing verification tools to be adapted to a more flexible format so that they may be treated as components. A system incorporating such tools becomes another component that can be embedded in an application. This paper describes the Prosper Toolkit which enables this. The nature of communication between components is specified in a language-independent way. It is implemented in several common programming languages to allow a wide variety of tools to have access to the toolkit.
Boolean satisfiability in electronic design automation
- Design Automation Conf
, 2000
"... Boolean Satisfiability (SAT) is often used as the underlying model for a significant and increasing number of applications in Electronic Design Automation (EDA) as well as in many other fields of Computer Science and Engineering. In recent years, new and efficient algorithms for SAT have been devel ..."
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Cited by 27 (0 self)
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Boolean Satisfiability (SAT) is often used as the underlying model for a significant and increasing number of applications in Electronic Design Automation (EDA) as well as in many other fields of Computer Science and Engineering. In recent years, new and efficient algorithms for SAT have been developed, allowing much larger problem instances to be solved. SAT “packages” are currently expected to have an impact on EDA applications similar to that of BDD packages since their introduction more than a decade ago. This tutorial paper is aimed at introducing the EDA professional to the Boolean satisfiability problem. Specifically, we highlight the use of SAT models to formulate a number of EDA problems in such diverse areas as test pattern generation, circuit delay computation, logic optimization, combinational equivalence checking, bounded model checking and functional test vector generation, among others. In addition, we provide an overview of the algorithmic techniques commonly used for solving SAT, including those that have seen widespread use in specific EDA applications. We categorize these algorithmic techniques, indicating which have been shown to be best suited for which tasks.
Improving safety assessment of complex systems: An industrial case study
- Proceedings of Formal Methods 2003 (LNCS 2805
, 2003
"... Abstract. The complexity of embedded controllers is steadily increasing. This trend, stimulated by the continuous improvement of the computational power of hardware, demands for a corresponding increase in the capability of design and safety engineers to maintain adequate safety levels. The use of f ..."
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Cited by 23 (6 self)
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Abstract. The complexity of embedded controllers is steadily increasing. This trend, stimulated by the continuous improvement of the computational power of hardware, demands for a corresponding increase in the capability of design and safety engineers to maintain adequate safety levels. The use of formal methods during system design has proved to be effective in several practical applications. However, the development of certain classes of applications, like, for instance, avionics systems, also requires the behaviour of a system to be analysed under certain degraded situations (e.g., when some components are not working as expected). The integration of system design activities with safety assessment and the use of formal methods, although not new, are still at an early stage. These goals are addressed by the ESACS project, a European-Union-sponsored project grouping several industrial companies from the aeronautic field. The ESACS project is developing a methodology and a platform the ESACS platform that helps safety engineers automating certain phases of their work. This paper reports on the application of the ESACS methodology and on the use of the ESACS platform to a case study, namely, the Secondary Power System of the Eurofighter Typhoon aircraft.
Experimental Analysis of Different Techniques for Bounded Model Checking
- Proc. of the 9 th TACAS, volume 2619 of LNCS
, 2003
"... Abstract. Bounded model checking (BMC) is a procedure that searches for counterexamples to a given property through bounded executions of a non-terminating system. This paper compares the performance of SAT-based, BDD-based and explicit state based BMC on benchmarks drawn from commercial designs. Ou ..."
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Cited by 21 (1 self)
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Abstract. Bounded model checking (BMC) is a procedure that searches for counterexamples to a given property through bounded executions of a non-terminating system. This paper compares the performance of SAT-based, BDD-based and explicit state based BMC on benchmarks drawn from commercial designs. Our experimental framework provides a uniform and comprehensive basis to evaluate each of these approaches. The experimental results in this paper suggest that for designs with deep counterexamples, BDD-based BMC is much faster. For designs with shallow counterexamples, we observe that indeed SAT-based BMC is more effective than BDD-based BMC, but we also observe that explicit state based BMC is comparably effective, a new observation. 1
A Method for Symbolic Computation of Abstract Operations ⋆
"... Abstract. In 1979, Cousot and Cousot gave a specification of the best (most-precise) abstract transformer possible for a given concrete transformer and a given abstract domain. Unfortunately, their specification does not lead to an algorithm for obtaining the best transformer. In fact, algorithms ar ..."
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Cited by 13 (2 self)
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Abstract. In 1979, Cousot and Cousot gave a specification of the best (most-precise) abstract transformer possible for a given concrete transformer and a given abstract domain. Unfortunately, their specification does not lead to an algorithm for obtaining the best transformer. In fact, algorithms are known for only a few abstract domains. domain A and logic L, computes successively better A values that overapproximate the set of states defined by an arbitrary formula in L. Because the method approaches the most-precise A value from “above”, if it is taking too much time, a safe answer can be returned at any time. For certain combinations of A and L, the framework is complete—i.e., with enough resources, it computes the most-precise abstract value possible. 1
A thread of HOL development
- Computer Journal
"... The HOL system is a mechanized proof assistant for higher order logic that has been under continuous development since the mid-1980s, by an ever-changing group of developers and external contributors. We give a brief overview of various implementations of the HOL logic before focusing on the evoluti ..."
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Cited by 13 (7 self)
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The HOL system is a mechanized proof assistant for higher order logic that has been under continuous development since the mid-1980s, by an ever-changing group of developers and external contributors. We give a brief overview of various implementations of the HOL logic before focusing on the evolution of certain important features available in a recent implementation. We also illustrate how the module system of Standard ML provided security and modularity in the construction of the HOL kernel, as well as serving in a separate capacity as a useful representation medium for persistent, hierarchical logical theories.
A generalization of St˚almarck’s method
, 2011
"... Abstract. This paper gives an account of St˚almarck’s method for validity checking of propositional-logic formulas, and explains each of the key components in terms of concepts from thefield of abstract interpretation. We then use these insights to present a framework for propositional-logic validit ..."
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Cited by 13 (9 self)
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Abstract. This paper gives an account of St˚almarck’s method for validity checking of propositional-logic formulas, and explains each of the key components in terms of concepts from thefield of abstract interpretation. We then use these insights to present a framework for propositional-logic validity-checking algorithms that is parametrized by an abstract domain and operations on that domain. St˚almarck’s method is one instantiation of the framework; other instantiations lead to new decision procedures for propositional logic. 1
