The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Joao Marquessilva - One of the best experts on this subject based on the ideXlab platform.
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fast flexible Mus enumeration
Constraints - An International Journal, 2016Co-Authors: Mark H Liffiton, Alessandro Previti, Ammar Malik, Joao MarquessilvaAbstract:The problem of enumerating minimal unsatisfiable subsets (Muses) of an infeasible constraint system is challenging due first to the complexity of computing even a single Mus and second to the potentially intractable number of Muses an instance may contain. In the face of the latter issue, when complete enumeration is not feasible, a partial enumeration of Muses can be valuable, ideally with a time cost for each Mus output no greater than that needed to extract a single Mus. Recently, two papers independently presented a new Mus enumeration algorithm well suited to partial Mus enumeration (Liffiton and Malik, 2013, Previti and Marques-Silva, 2013). The algorithm exhibits good anytime performance, steadily producing Muses throughout its execution; it is constraint agnostic, applying equally well to any type of constraint system; and its flexible structure allows it to incorporate advances in single Mus extraction algorithms and eases the creation of further improvements and modifications. This paper unifies and expands upon the earlier work, presenting a detailed explanation of the algorithm's operation in a framework that also enables clearer comparisons to previous approaches, and we present a new optimization of the algorithm as well. Expanded experimental results illustrate the algorithm's improvement over past approaches and newly explore some of its variants.
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smallest Mus extraction with minimal hitting set dualization
Principles and Practice of Constraint Programming, 2015Co-Authors: Alexey Ignatiev, Alessandro Previti, Mark H Liffiton, Joao MarquessilvaAbstract:Minimal explanations of infeasibility are of great interest in many domains. In propositional logic, these are referred to as Minimal Unsatisfiable Subsets Muses. An unsatisfiable formula can have multiple Muses, some of which provide more insights than others. Different criteria can be considered in order to identify a good minimal explanation. Among these, the size of an Mus is arguably one of the most intuitive. Moreover, computing the smallest Mus SMus finds several practical applications that include validating the quality of the Muses computed by Mus extractors and finding equivalent subformulae of smallest size, among others. This paper develops a novel algorithm for computing a smallest Mus, and we show that it outperforms all the previous alternatives pushing the state of the art in SMus solving. Although described in the context of propositional logic, the presented technique can also be applied to other constraint systems.
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partial Mus enumeration
National Conference on Artificial Intelligence, 2013Co-Authors: Alessandro Previti, Joao MarquessilvaAbstract:Minimal explanations of infeasibility find a wide range of uses. In the Boolean domain, these are referred to as Minimal Unsatisfiable Subsets (Muses). In some settings, one needs to enumerate Muses of a Boolean formula. Most often the goal is to enumerate all Muses. In cases where this is computationally infeasible, an alternative is to enumerate some Muses. This paper develops a novel approach for partial enumeration of Muses, that complements existing alternatives. If the enumeration of all Muses is viable, then existing alternatives represent the best option. However, for formulas where the enumeration of all Muses is unrealistic, our approach provides a solution for enumerating some Muses within a given time bound. The experimental results focus on formulas for which existing solutions are unable to enumerate Muses, and shows that the new approach can in most cases enumerate a nonnegligible number of Muses within a given time bound.
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Muser2 an efficient Mus extractor
Journal on Satisfiability Boolean Modeling and Computation, 2012Co-Authors: Anton Belov, Joao MarquessilvaAbstract:Algorithms for extraction of Minimally Unsatisfiable Subformulas (Muses) of CNF formulas find a wide range of practical applications, including product configuration, knowledge-based validation, hardware and software design and verification. This paper describes the Mus extractor Muser2. Muser2 implements a wide range of Mus extraction algorithms, integrates a number of key optimization techniques, and represents the current state-of-the-art in Mus extraction.
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towards efficient Mus extraction
Ai Communications, 2012Co-Authors: Anton Belov, Ines Lynce, Joao MarquessilvaAbstract:Minimally Unsatisfiable Subformulas (Mus) find a wide range of practical applications, including product configuration, knowledge-based validation, and hardware and software design and verification. Muses also find application in recent Maximum Satisfiability algorithms and in CNF formula redundancy removal. Besides direct applications in Propositional Logic, algorithms for Mus extraction have been applied to more expressive logics. This paper proposes two algorithms for computation of Muses of propositional formulas in Conjunctive Normal Form (CNF). The first algorithm is optimal in its class, meaning that it requires the smallest number of calls to a SAT solver. The second algorithm extends earlier work, but implements a number of new techniques. Among these, this paper analyzes in detail the technique of recursive model rotation, which provides significant performance gains in practice. Experimental results, obtained on representative practical benchmarks, indicate that the new algorithms achieve significant performance gains with respect to state of the art Mus extraction algorithms.
Mark H Liffiton - One of the best experts on this subject based on the ideXlab platform.
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fast flexible Mus enumeration
Constraints - An International Journal, 2016Co-Authors: Mark H Liffiton, Alessandro Previti, Ammar Malik, Joao MarquessilvaAbstract:The problem of enumerating minimal unsatisfiable subsets (Muses) of an infeasible constraint system is challenging due first to the complexity of computing even a single Mus and second to the potentially intractable number of Muses an instance may contain. In the face of the latter issue, when complete enumeration is not feasible, a partial enumeration of Muses can be valuable, ideally with a time cost for each Mus output no greater than that needed to extract a single Mus. Recently, two papers independently presented a new Mus enumeration algorithm well suited to partial Mus enumeration (Liffiton and Malik, 2013, Previti and Marques-Silva, 2013). The algorithm exhibits good anytime performance, steadily producing Muses throughout its execution; it is constraint agnostic, applying equally well to any type of constraint system; and its flexible structure allows it to incorporate advances in single Mus extraction algorithms and eases the creation of further improvements and modifications. This paper unifies and expands upon the earlier work, presenting a detailed explanation of the algorithm's operation in a framework that also enables clearer comparisons to previous approaches, and we present a new optimization of the algorithm as well. Expanded experimental results illustrate the algorithm's improvement over past approaches and newly explore some of its variants.
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Parallelizing Partial Mus Enumeration
2016 IEEE 28th International Conference on Tools with Artificial Intelligence (ICTAI), 2016Co-Authors: Wenting Zhao, Mark H LiffitonAbstract:The problem of enumerating minimal unsatisfiable subsets of a constraint system (Muses) is a natural candidate for parallelization: as an enumeration problem, it allows for concurrent solving of independent subproblems, and as a typically intractable problem w.r.t. completion (which parallelization cannot transcend), the speed or rate of output (which parallelization can improve) is often the most important performance characteristic. In this work, we explore the parallelization of partial Mus enumeration (aiming to enumerate some Muses within given resource constraints) via two extensions to a recently-developed sequential algorithm - one employing an existing parallel single-Mus extraction algorithm, the other parallelizing the entire enumeration algorithm-- and we discuss variants and implementation details as well. Results of experiments run with up to 16 cores show that the full parallelization of the entire enumeration algorithm scales well, reaching an average of 92% of perfect scaling with 4 cores and 70% at 16 cores. Evaluating variants and implementation details illuminates how those choices impact performance, including a potentially counterintuitive result that sharing results between threads to avoid duplicate work is not beneficial in the general case.
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smallest Mus extraction with minimal hitting set dualization
Principles and Practice of Constraint Programming, 2015Co-Authors: Alexey Ignatiev, Alessandro Previti, Mark H Liffiton, Joao MarquessilvaAbstract:Minimal explanations of infeasibility are of great interest in many domains. In propositional logic, these are referred to as Minimal Unsatisfiable Subsets Muses. An unsatisfiable formula can have multiple Muses, some of which provide more insights than others. Different criteria can be considered in order to identify a good minimal explanation. Among these, the size of an Mus is arguably one of the most intuitive. Moreover, computing the smallest Mus SMus finds several practical applications that include validating the quality of the Muses computed by Mus extractors and finding equivalent subformulae of smallest size, among others. This paper develops a novel algorithm for computing a smallest Mus, and we show that it outperforms all the previous alternatives pushing the state of the art in SMus solving. Although described in the context of propositional logic, the presented technique can also be applied to other constraint systems.
Jacob L Mueller - One of the best experts on this subject based on the ideXlab platform.
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large x linked palindromes undergo arm to arm gene conversion across Mus lineages
Molecular Biology and Evolution, 2020Co-Authors: Callie M Swanepoel, Emma R Gerlinger, Jacob L MuellerAbstract:Large (>10kb), nearly-identical (>99% nucleotide identity), palindromic sequences are enriched on mammalian sex chromosomes. Primate Y-palindromes undergo high rates of arm-to-arm gene conversion, a proposed mechanism for maintaining their sequence integrity in the absence of X-Y recombination. It is unclear whether X-palindromes, which can freely recombine in females, undergo arm-to-arm gene conversion and, if so, at what rate. We generated high-quality sequence assemblies of Mus molossinus and Mus spretus X-palindromic regions and compared them to orthologous Mus Musculus X-palindromes. Our evolutionary sequence comparisons find evidence of X-palindrome arm-to-arm gene conversion at rates comparable to autosomal allelic gene conversion rates in mice. Mus X-palindromes also carry more derived than ancestral variants between species, suggesting their sequence is rapidly diverging. We speculate that in addition to maintaining genes' sequence integrity via sequence homogenization, palindrome arm-to-arm gene conversion may also facilitate rapid sequence divergence.
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large x linked palindromes undergo arm to arm gene conversion across Mus lineages
bioRxiv, 2019Co-Authors: Callie M Swanepoel, Emma R Gerlinger, Jacob L MuellerAbstract:Large (>10kb), nearly-identical (>99% nucleotide identity), palindromic sequences are enriched on mammalian sex chromosomes. Primate Y-palindromes undergo high rates of arm-to-arm gene conversion, a proposed mechanism for maintaining their sequence integrity in the absence of X-Y recombination. It is unclear whether X-palindromes, which can freely recombine in females, undergo arm-to-arm gene conversion and, if so, at what rate. We generated high quality sequence assemblies of Mus molossinus and Mus spretus X-palindromic regions and compared them to orthologous Mus Musculus X-palindromes. Our evolutionary sequence comparisons found evidence of X-palindrome arm-to-arm gene conversion at rates comparable to rates of autosomal allelic gene conversion in mice. Mus X-palindrome genes also exhibit higher than expected sequence diversification, indicating gene conversion may facilitate the rapid evolution of palindrome-associated genes. We conclude that in addition to maintaining genes sequence integrity via sequence homogenization, arm-to-arm gene conversion can also rapidly drive genetic evolution via sequence diversification.
Joao Marques-silva - One of the best experts on this subject based on the ideXlab platform.
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SAT - Parallel Mus extraction
Theory and Applications of Satisfiability Testing – SAT 2013, 2013Co-Authors: Anton Belov, Norbert Manthey, Joao Marques-silvaAbstract:Parallelization is a natural direction towards the improvements in the scalability of algorithms for the computation of Minimally Unsatisfiable Subformulas (Muses), and group-Muses, of CNF formulas. In this paper we propose and analyze a number of approaches to parallel Mus computation. Just as it is the case with the parallel CDCL-based SAT solving, the communication, i.e. the exchange of learned clauses between the solvers running in parallel, emerges as an important component of parallel Mus extraction algorithms. However, in the context of Mus computation the communication might be unsound. We argue that the assumption-based approach to the incremental CDCL-based SAT solving is the key enabling technology for effective sound communication in the context of parallel Mus extraction, and show that fully unrestricted communication is possible in this setting. Furthermore, we propose a number of techniques to improve the quality of communication, as well as the quality of job distribution in the parallel Mus extractor. We evaluate the proposed techniques empirically on industrially-relevant instances of both plain and group Mus problems, and demonstrate significant (up to an order of magnitude) improvements due to the parallelization.
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TACAS - Formula preprocessing in Mus extraction
Tools and Algorithms for the Construction and Analysis of Systems, 2013Co-Authors: Anton Belov, Matti Järvisalo, Joao Marques-silvaAbstract:Efficient algorithms for extracting minimally unsatisfiable subformulas (Muses) of Boolean formulas find a wide range of applications in the analysis of systems, e.g., hardware and software bounded model checking. In this paper we study the applicability of preprocessing techniques for Boolean satisfiability (SAT) in the context of Mus extraction. Preprocessing has proven to be extremely important in enabling more efficient SAT solving. Hence the study of the applicability and the effectiveness of preprocessing in Mus extraction is highly relevant. Considering the extraction of both standard and group Muses, we focus on a number of SAT preprocessing techniques, and formally prove to what extent the techniques can be directly applied in the context of Mus extraction. Furthermore, we develop a generic theoretical framework that captures Mus extraction problems, and enables formalizing conditions for correctness-preserving applications of preprocessing techniques that are not applicable directly. We experimentally evaluate the effect of preprocessing in the context of group Mus extraction.
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FMCAD - Accelerating Mus extraction with recursive model rotation
2011Co-Authors: Anton Belov, Joao Marques-silvaAbstract:Minimally Unsatisfiable Subformulas (Muses) find a wide range of practical applications. A large number of Mus extraction algorithms have been proposed over the last decade, and most of these algorithms are based on iterative calls to a SAT solver. In this paper we introduce a powerful technique for acceleration of Mus extraction algorithms called recursive model rotation — a recursive version of the recently proposed model rotation technique. We demonstrate empirically that recursive model rotation leads to multiple orders of magnitude performance improvements on practical instances, and pushes the performance of our Mus extractor Muser2 ahead of the currently available Mus extraction tools.
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CP - On deciding Mus membership with QBF
Principles and Practice of Constraint Programming – CP 2011, 2011Co-Authors: Mikoláš Janota, Joao Marques-silvaAbstract:This paper tackles the problem of deciding whether a given clause belongs to some minimally unsatisfiable subset (Mus) of a formula, where the formula is in conjunctive normal form (CNF) and unsatisfiable. Deciding Mus-membership helps the understanding of why a formula is unsatisfiable. If a clause does not belong to any Mus, then removing it will certainly not contribute to restoring the formula's consistency. Unsatisfiable formulas and consistency restoration in particular have a number of practical applications in areas such as software verification or product configuration. The Mus-membership problem is known to be in the second level of polynomial hierarchy, more precisely it is Σ2P -complete. Hence, quantified Boolean formulas (QBFs) represent a possible avenue for tackling the problem. This paper develops a number of novel QBF formulations of the Mus-membership problem and evaluates their practicality using modern off-the-shelf solvers.
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Accelerating Mus extraction with recursive model rotation
2011 Formal Methods in Computer-Aided Design (FMCAD), 2011Co-Authors: Anton Belov, Joao Marques-silvaAbstract:Minimally Unsatisfiable Subformulas (Muses) find a wide range of practical applications. A large number of Mus extraction algorithms have been proposed over the last decade, and most of these algorithms are based on iterative calls to a SAT solver. In this paper we introduce a powerful technique for acceleration of Mus extraction algorithms called recursive model rotation - a recursive version of the recently proposed model rotation technique. We demonstrate empirically that recursive model rotation leads to multiple orders of magnitude performance improvements on practical instances, and pushes the performance of our Mus extractor Muser2 ahead of the currently available Mus extraction tools.
Yixin Zhang - One of the best experts on this subject based on the ideXlab platform.
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Interoperability test for IEC 61850-9-2 standard-based merging units
2017 IEEE Power & Energy Society Innovative Smart Grid Technologies Conference (ISGT), 2017Co-Authors: Eugene Y. Song, Gerald J. Fitzpatrick, Yixin ZhangAbstract:Merging units (Mus) sample alternating current (AC) in one or multiple phases and convert these analog voltage and current signals to digital values and transmit the sampled values (SVs) to protection relays (PRs) and bay controllers (BCs) through either Ethernet or optical communication channels based on the IEC 61850-9-2 protocol. Mus could provide real-time data for current, voltage, and status of power grids, and therefore, they can play a key role in real-time monitoring, protection, and control of the grids. However, MU data exchange, sharing, and interoperability can pose major challenges for the power industry. With the standardization of MU data formats, interfaces, and communication protocols, it is hopeful that data interoperability of Mus can be achieved via the IEC 61850-9-2 standard. Nevertheless, Mus and PRs produced by different vendors may not be interoperable, even though they might conform to the IEC 61850-9-2 standards. Meanwhile, another challenge is how to assure the interoperability of Mus and the best way to achieve that is through MU interoperability testing. This paper proposes a passive interoperability test method for IEC 61850-9-2 based Mus. It mainly focuses on monitoring the communications and capturing the packets between the device under test (DUT) or MU, and the MU tester or PR, and analyzing the interoperability of Mus based on the packets captured. The interoperability test system consists of five parts: a MU tester, a DUT, a network switch, a network sniffer, and a MU interoperability analyzer. IEC 61850-9-2 provides an interoperability test suite that includes a number of test cases. Two commercial Mus from different vendors have been tested with the MU Tester over Ethernet based on the interoperability test method proposed. Test results of a test case for sending SVs are provided
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Interoperability test for IEC 61850-9-2 standard-based merging units
2017 IEEE Power and Energy Society Innovative Smart Grid Technologies Conference ISGT 2017, 2017Co-Authors: Eugene Y. Song, Kang B. Lee, Gerald J. Fitzpatrick, Yixin ZhangAbstract:Merging units (Mus) sample alternating current (AC) in one or multiple phases and convert these analog voltage and current signals to digital values and transmit the sampled values (SVs) to protection relays (PRs) and bay controllers (BCs) through either Ethernet or optical communication channels based on the IEC 61850-9-2 protocol. Mus could provide real-time data for current, voltage, and status of power grids, and therefore, they can play a key role in real-time monitoring, protection, and control of the grids. However, MU data exchange, sharing, and interoperability can pose major challenges for the power industry. With the standardization of MU data formats, interfaces, and communication protocols, it is hopeful that data interoperability of Mus can be achieved via the IEC 61850-9-2 standard. Nevertheless, Mus and PRs produced by different vendors may not be interoperable, even though they might conform to the IEC 61850-9-2 standards. Meanwhile, another challenge is how to assure the interoperability of Mus and the best way to achieve that is through MU interoperability testing. This paper proposes a passive interoperability test method for IEC 61850-9-2 based Mus. It mainly focuses on monitoring the communications and capturing the packets between the device under test (DUT) or MU, and the MU tester or PR, and analyzing the interoperability of Mus based on the packets captured. The interoperability test system consists of five parts: a MU tester, a DUT, a network switch, a network sniffer, and a MU interoperability analyzer. IEC 61850-9-2 provides an interoperability test suite that includes a number of test cases. Two commercial Mus from different vendors have been tested with the MU Tester over Ethernet based on the interoperability test method proposed. Test results of a test case for sending SVs are provided. Index
