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Author Chierichetti, Flavio; Lattanzi, Silvio; Mari, Federico; Panconesi, Alessandro pdf  doi
openurl 
  Title On Placing Skips Optimally in Expectation Type Conference Article
  Year 2008 Publication Web Search and Web Data Mining (WSDM 2008) Abbreviated Journal  
  Volume Issue Pages 15-24  
  Keywords Information Retrieval  
  Abstract We study the problem of optimal skip placement in an inverted list. Assuming the query distribution to be known in advance, we formally prove that an optimal skip placement can be computed quite efficiently. Our best algorithm runs in time O(n log n), n being the length of the list. The placement is optimal in the sense that it minimizes the expected time to process a query. Our theoretical results are matched by experiments with a real corpus, showing that substantial savings can be obtained with respect to the tra- ditional skip placement strategy, that of placing consecutive skips, each spanning sqrt(n) many locations.  
  Address  
  Corporate Author Thesis  
  Publisher Acm Place of Publication Editor Najork, M.; Broder, A.Z.; Chakrabarti, S.  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Sapienza @ mari @ ChiLatMar08 Serial (down) 94  
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Author Mari, Federico; Melatti, Igor; Salvo, Ivano; Tronci, Enrico; Alvisi, Lorenzo; Clement, Allen; Li, Harry pdf  doi
openurl 
  Title Model Checking Nash Equilibria in MAD Distributed Systems Type Conference Article
  Year 2008 Publication FMCAD '08: Proceedings of the 2008 International Conference on Formal Methods in Computer-Aided Design Abbreviated Journal  
  Volume Issue Pages 1-8  
  Keywords Model Checking, MAD Distributed System, Nash Equilibrium  
  Abstract We present a symbolic model checking algorithm for verification of Nash equilibria in finite state mechanisms modeling Multiple Administrative Domains (MAD) distributed systems. Given a finite state mechanism, a proposed protocol for each agent and an indifference threshold for rewards, our model checker returns PASS if the proposed protocol is a Nash equilibrium (up to the given indifference threshold) for the given mechanism, FAIL otherwise. We implemented our model checking algorithm inside the NuSMV model checker and present experimental results showing its effectiveness for moderate size mechanisms. For example, we can handle mechanisms which corresponding normal form games would have more than $10^20$ entries. To the best of our knowledge, no model checking algorithm for verification of mechanism Nash equilibria has been previously published.  
  Address  
  Corporate Author Thesis  
  Publisher IEEE Press Place of Publication Piscataway, NJ, USA Editor Cimatti, A.; Jones, R.  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 978-1-4244-2735-2 ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Sapienza @ mari @ MarMelSalTroAlvCle08 Serial (down) 93  
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Author Mari, Federico; Tronci, Enrico pdf  doi
openurl 
  Title CEGAR Based Bounded Model Checking of Discrete Time Hybrid Systems Type Conference Article
  Year 2007 Publication Hybrid Systems: Computation and Control (HSCC 2007) Abbreviated Journal  
  Volume Issue Pages 399-412  
  Keywords Model Checking, Abstraction, CEGAR, SAT, Hybrid Systems, DTHS  
  Abstract Many hybrid systems can be conveniently modeled as Piecewise Affine Discrete Time Hybrid Systems PA-DTHS. As well known Bounded Model Checking (BMC) for such systems comes down to solve a Mixed Integer Linear Programming (MILP) feasibility problem. We present a SAT based BMC algorithm for automatic verification of PA-DTHSs. Using Counterexample Guided Abstraction Refinement (CEGAR) our algorithm gradually transforms a PA-DTHS verification problem into larger and larger SAT problems. Our experimental results show that our approach can handle PA-DTHSs that are more then 50 times larger than those that can be handled using a MILP solver.  
  Address  
  Corporate Author Thesis  
  Publisher Springer Place of Publication Editor Bemporad, A.; Bicchi, A.; Buttazzo, G.C.  
  Language Summary Language Original Title  
  Series Editor Series Title Lecture Notes in Computer Science Abbreviated Series Title  
  Series Volume 4416 Series Issue Edition  
  ISSN ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Sapienza @ mari @ MarTro07 Serial (down) 92  
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Author Della Penna, Giuseppe; Intrigila, Benedetto; Melatti, Igor; Tronci, Enrico; Venturini Zilli, Marisa pdf  doi
openurl 
  Title Exploiting Transition Locality in Automatic Verification of Finite State Concurrent Systems Type Journal Article
  Year 2004 Publication Sttt Abbreviated Journal  
  Volume 6 Issue 4 Pages 320-341  
  Keywords  
  Abstract In this paper we show that statistical properties of the transition graph of a system to be verified can be exploited to improve memory or time performances of verification algorithms. We show experimentally that protocols exhibit transition locality. That is, with respect to levels of a breadth-first state space exploration, state transitions tend to be between states belonging to close levels of the transition graph. We support our claim by measuring transition locality for the set of protocols included in the Mur$\varphi$ verifier distribution. We present a cache-based verification algorithm that exploits transition locality to decrease memory usage and a disk-based verification algorithm that exploits transition locality to decrease disk read accesses, thus reducing the time overhead due to disk usage. Both algorithms have been implemented within the Mur$\varphi$ verifier. Our experimental results show that our cache-based algorithm can typically save more than 40% of memory with an average time penalty of about 50% when using (Mur$\varphi$) bit compression and 100% when using bit compression and hash compaction, whereas our disk-based verification algorithm is typically more than ten times faster than a previously proposed disk-based verification algorithm and, even when using 10% of the memory needed to complete verification, it is only between 40 and 530% (300% on average) slower than (RAM) Mur$\varphi$ with enough memory to complete the verification task at hand. Using just 300 MB of memory our disk-based Mur$\varphi$ was able to complete verification of a protocol with about $10^9$ reachable states. This would require more than 5 GB of memory using standard Mur$\varphi$.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Sapienza @ mari @ DIMTZ04j Serial (down) 91  
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Author Della Penna, Giuseppe; Intrigila, Benedetto; Melatti, Igor; Tronci, Enrico; Venturini Zilli, Marisa pdf  doi
openurl 
  Title Finite Horizon Analysis of Stochastic Systems with the Mur$\varphi$ Verifier Type Conference Article
  Year 2003 Publication Theoretical Computer Science, 8th Italian Conference, ICTCS 2003, Bertinoro, Italy, October 13-15, 2003, Proceedings Abbreviated Journal  
  Volume Issue Pages 58-71  
  Keywords  
  Abstract Many reactive systems are actually Stochastic Processes. Automatic analysis of such systems is usually very difficult thus typically one simplifies the analysis task by using simulation or by working on a simplified model (e.g. a Markov Chain). We present a Finite Horizon Probabilistic Model Checking approach which essentially can handle the same class of stochastic processes of a typical simulator. This yields easy modeling of the system to be analyzed together with formal verification capabilities. Our approach is based on a suitable disk based extension of the Mur$\varphi$ verifier. Moreover we present experimental results showing effectiveness of our approach.  
  Address  
  Corporate Author Thesis  
  Publisher Springer Place of Publication Editor Blundo, C.; Laneve, C.  
  Language Summary Language Original Title  
  Series Editor Series Title Lecture Notes in Computer Science Abbreviated Series Title  
  Series Volume 2841 Series Issue Edition  
  ISSN 3-540-20216-1 ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Sapienza @ mari @ DIMTZ03c Serial (down) 90  
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Author Della Penna, Giuseppe; Intrigila, Benedetto; Melatti, Igor; Minichino, Michele; Ciancamerla, Ester; Parisse, Andrea; Tronci, Enrico; Venturini Zilli, Marisa pdf  doi
openurl 
  Title Automatic Verification of a Turbogas Control System with the Mur$\varphi$ Verifier Type Conference Article
  Year 2003 Publication Hybrid Systems: Computation and Control, 6th International Workshop, HSCC 2003 Prague, Czech Republic, April 3-5, 2003, Proceedings Abbreviated Journal  
  Volume Issue Pages 141-155  
  Keywords  
  Abstract Automatic analysis of Hybrid Systems poses formidable challenges both from a modeling as well as from a verification point of view. We present a case study on automatic verification of a Turbogas Control System (TCS) using an extended version of the Mur$\varphi$ verifier. TCS is the heart of ICARO, a 2MW Co-generative Electric Power Plant. For large hybrid systems, as TCS is, the modeling effort accounts for a significant part of the whole verification activity. In order to ease our modeling effort we extended the Mur$\varphi$ verifier by importing the C language long double type (finite precision real numbers) into it. We give experimental results on running our extended Mur$\varphi$ on our TCS model. For example using Mur$\varphi$ we were able to compute an admissible range of values for the variation speed of the user demand of electric power to the turbogas.  
  Address  
  Corporate Author Thesis  
  Publisher Springer Place of Publication Editor Maler, O.; Pnueli, A.  
  Language Summary Language Original Title  
  Series Editor Series Title Lecture Notes in Computer Science Abbreviated Series Title  
  Series Volume 2623 Series Issue Edition  
  ISSN 3-540-00913-2 ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Sapienza @ mari @ Dimmcptz03 Serial (down) 88  
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Author Della Penna, Giuseppe; Intrigila, Benedetto; Melatti, Igor; Tronci, Enrico; Venturini Zilli, Marisa pdf  doi
openurl 
  Title Bounded Probabilistic Model Checking with the Mur$\varphi$ Verifier Type Conference Article
  Year 2004 Publication Formal Methods in Computer-Aided Design, 5th International Conference, FMCAD 2004, Austin, Texas, USA, November 15-17, 2004, Proceedings Abbreviated Journal  
  Volume Issue Pages 214-229  
  Keywords  
  Abstract In this paper we present an explicit verification algorithm for Probabilistic Systems defining discrete time/finite state Markov Chains. We restrict ourselves to verification of Bounded PCTL formulas (BPCTL), that is, PCTL formulas in which all Until operators are bounded, possibly with different bounds. This means that we consider only paths (system runs) of bounded length. Given a Markov Chain $\cal M$ and a BPCTL formula Φ, our algorithm checks if Φ is satisfied in $\cal M$. This allows to verify important properties, such as reliability in Discrete Time Hybrid Systems. We present an implementation of our algorithm within a suitable extension of the Mur$\varphi$ verifier. We call FHP-Mur$\varphi$ (Finite Horizon Probabilistic Mur$\varphi$) such extension of the Mur$\varphi$ verifier. We give experimental results comparing FHP-Mur$\varphi$ with (a finite horizon subset of) PRISM, a state-of-the-art symbolic model checker for Markov Chains. Our experimental results show that FHP-Mur$\varphi$ can effectively handle verification of BPCTL formulas for systems that are out of reach for PRISM, namely those involving arithmetic operations on the state variables (e.g. hybrid systems).  
  Address  
  Corporate Author Thesis  
  Publisher Springer Place of Publication Editor Hu, A.J.; Martin, A.K.  
  Language Summary Language Original Title  
  Series Editor Series Title Lecture Notes in Computer Science Abbreviated Series Title  
  Series Volume 3312 Series Issue Edition  
  ISSN 3-540-23738-0 ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Sapienza @ mari @ Dimtz04 Serial (down) 87  
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Author Della Penna, Giuseppe; Intrigila, Benedetto; Melatti, Igor; Tronci, Enrico; Venturini Zilli, Marisa pdf  doi
openurl 
  Title Integrating RAM and Disk Based Verification within the Mur$\varphi$ Verifier Type Conference Article
  Year 2003 Publication Correct Hardware Design and Verification Methods, 12th IFIP WG 10.5 Advanced Research Working Conference, CHARME 2003, L'Aquila, Italy, October 21-24, 2003, Proceedings Abbreviated Journal  
  Volume Issue Pages 277-282  
  Keywords  
  Abstract We present a verification algorithm that can automatically switch from RAM based verification to disk based verification without discarding the work done during the RAM based verification phase. This avoids having to choose beforehand the proper verification algorithm. Our experimental results show that typically our integrated algorithm is as fast as (sometime faster than) the fastest of the two base (i.e. RAM based and disk based) verification algorithms.  
  Address  
  Corporate Author Thesis  
  Publisher Springer Place of Publication Editor Geist, D.; Tronci, E.  
  Language Summary Language Original Title  
  Series Editor Series Title Lecture Notes in Computer Science Abbreviated Series Title  
  Series Volume 2860 Series Issue Edition  
  ISSN 3-540-20363-X ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Sapienza @ mari @ DIMTZ03a Serial (down) 85  
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Author Della Penna, Giuseppe; Intrigila, Benedetto; Melatti, Igor; Tronci, Enrico; Venturini Zilli, Marisa pdf  doi
openurl 
  Title Finite Horizon Analysis of Markov Chains with the Mur$\varphi$ Verifier Type Conference Article
  Year 2003 Publication Correct Hardware Design and Verification Methods, 12th IFIP WG 10.5 Advanced Research Working Conference, CHARME 2003, L'Aquila, Italy, October 21-24, 2003, Proceedings Abbreviated Journal  
  Volume Issue Pages 394-409  
  Keywords  
  Abstract In this paper we present an explicit disk based verification algorithm for Probabilistic Systems defining discrete time/finite state Markov Chains. Given a Markov Chain and an integer k (horizon), our algorithm checks whether the probability of reaching an error state in at most k steps is below a given threshold. We present an implementation of our algorithm within a suitable extension of the Mur$\varphi$ verifier. We call the resulting probabilistic model checker FHP-Mur$\varphi$ (Finite Horizon Probabilistic Mur$\varphi$). We present experimental results comparing FHP-Mur$\varphi$ with (a finite horizon subset of) PRISM, a state-of-the-art symbolic model checker for Markov Chains. Our experimental results show that FHP-Mur$\varphi$ can handle systems that are out of reach for PRISM, namely those involving arithmetic operations on the state variables (e.g. hybrid systems).  
  Address  
  Corporate Author Thesis  
  Publisher Springer Place of Publication Editor Geist, D.; Tronci, E.  
  Language Summary Language Original Title  
  Series Editor Series Title Lecture Notes in Computer Science Abbreviated Series Title  
  Series Volume 2860 Series Issue Edition  
  ISSN 3-540-20363-X ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Sapienza @ mari @ Dimtz03 Serial (down) 84  
Permanent link to this record
 

 
Author Della Penna, Giuseppe; Intrigila, Benedetto; Melatti, Igor; Tronci, Enrico; Venturini Zilli, Marisa pdf  doi
openurl 
  Title Finite horizon analysis of Markov Chains with the Mur$\varphi$ verifier Type Journal Article
  Year 2006 Publication Int. J. Softw. Tools Technol. Transf. Abbreviated Journal  
  Volume 8 Issue 4 Pages 397-409  
  Keywords  
  Abstract In this paper we present an explicit disk-based verification algorithm for Probabilistic Systems defining discrete time/finite state Markov Chains. Given a Markov Chain and an integer k (horizon), our algorithm checks whether the probability of reaching an error state in at most k steps is below a given threshold. We present an implementation of our algorithm within a suitable extension of the Mur$\varphi$ verifier. We call the resulting probabilistic model checker FHP-Mur$\varphi$ (Finite Horizon Probabilistic Mur$\varphi$). We present experimental results comparing FHP-Mur$\varphi$ with (a finite horizon subset of) PRISM, a state-of-the-art symbolic model checker for Markov Chains. Our experimental results show that FHP-Mur$\varphi$ can handle systems that are out of reach for PRISM, namely those involving arithmetic operations on the state variables (e.g. hybrid systems).  
  Address  
  Corporate Author Thesis  
  Publisher Springer-Verlag Place of Publication Berlin, Heidelberg Editor  
  Language Summary Language Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1433-2779 ISBN Medium  
  Area Expedition Conference  
  Notes Approved yes  
  Call Number Sapienza @ mari @ Dimtz06 Serial (down) 78  
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