@phdthesis{4363, author = {Vasu Singh}, booktitle = {Formalizing and Verifying Transactional Memories}, publisher = {EPFL Lausanne}, title = {{Formalizing and Verifying Transactional Memories}}, year = {2009}, } @inproceedings{4365, abstract = {We present an abstraction refinement technique for the verification of universally quantified array assertions such as “all elements in the array are sorted”. Our technique can be seamlessly combined with existing software model checking algorithms. We implemented our technique in the ACSAR software model checker and successfully verified quantified array assertions for both text book examples and real-life examples taken from the Linux operating system kernel.}, author = {Seghir, Mohamed and Podelski, Andreas and Wies, Thomas}, booktitle = {16th International Symposium on Static Analysis}, location = {Los Angeles, CA, United States}, pages = {3 -- 18}, publisher = {Springer}, title = {{Abstraction refinement for quantified array assertions}}, doi = {10.1007/978-3-642-03237-0_3}, volume = {5673}, year = {2009}, } @inproceedings{4375, author = {Lahiri, Shuvendu and Qadeer, Shaz and Galeotti, Juan and Voung, Jan and Wies, Thomas}, booktitle = {21st International Conference on Computer Aided Verification}, location = {Grenoble, France}, pages = {493 -- 508}, publisher = {Springer}, title = {{Intra-module inference}}, doi = {10.1007/978-3-642-02658-4_37}, volume = {5643}, year = {2009}, } @article{4376, abstract = {We present Chorus, a high-level parallel programming model suitable for irregular, heap-manipulating applications like mesh refinement and epidemic simulations, and JChorus, an implementation of the model on top of Java. One goal of Chorus is to express the dynamic and instance-dependent patterns of memory access that are common in typical irregular applications. Its other focus is locality of effects: the property that in many of the same applications, typical imperative commands only affect small, local regions in the shared heap. Chorus addresses dynamism and locality through the unifying abstraction of an object assembly: a local region in a shared data structure equipped with a short-lived, speculative thread of control. The thread of control in an assembly can only access objects within the assembly. While objects can migrate from assembly to assembly, such migration is local--i.e., objects only move from one assembly to a neighboring one--and does not lead to aliasing. Programming primitives include a merge operation, by which an assembly merges with an adjacent assembly, and a split operation, which splits an assembly into smaller ones. Our abstractions are race and deadlock-free, and inherently data-centric. We demonstrate that Chorus and JChorus allow natural programming of several important applications exhibiting irregular data-parallelism. We also present an implementation of JChorus based on a many-to-one mapping of assemblies to lower-level threads, and report on preliminary performance numbers.}, author = {Lublinerman, Roberto and Chaudhuri, Swarat and Cerny, Pavol}, journal = {ACM SIGPLAN Notices}, number = {10}, pages = {61 -- 80}, publisher = {ACM}, title = {{Parallel programming with object assemblies}}, doi = {10.1145/1639949.164009}, volume = {44}, year = {2009}, } @inproceedings{4377, abstract = {Programming errors found early are the cheapest. Tools applying to the early stage of code development exist but either they suffer from false positives (“noise”) or they require strong user interaction. We propose to avoid this deficiency by defining a new class of errors. A program fragment is doomed if its execution will inevitably fail, in whatever state it is started. We use a formal verification method to identify such errors fully automatically and, most significantly, without producing noise. We report on preliminary experiments with a prototype tool.}, author = {Hoenicke, Jochen and Leino, K Rustan and Podelski, Andreas and Schäf, Martin and Wies, Thomas}, booktitle = {Second World Congress on Formal Methods}, location = {Eindhoven, The Netherlands}, pages = {338 -- 353}, publisher = {Springer}, title = {{It's doomed; we can prove it}}, doi = {10.1007/978-3-642-05089-3_22}, volume = {5850}, year = {2009}, } @inproceedings{4383, abstract = {Pseudo-code descriptions of STMs assume sequentially consistent program execution and atomicity of high-level STM operations like read, write, and commit. These assumptions are often violated in realistic settings, as STM implementations run on relaxed memory models, with the atomicity of operations as provided by the hardware. This paper presents the first approach to verify STMs under relaxed memory models with atomicity of 32 bit loads and stores, and read-modify-write operations. We present RML, a new high-level language for expressing concurrent algorithms with a hardware-level atomicity of instructions, and whose semantics is parametrized by various relaxed memory models. We then present our tool, FOIL, which takes as input the RML description of an STM algorithm and the description of a memory model, and automatically determines the locations of fences, which if inserted, ensure the correctness of the STM algorithm under the given memory model. We use FOIL to verify DSTM, TL2, and McRT STM under the memory models of sequential consistency, total store order, partial store order, and relaxed memory order.}, author = {Guerraoui, Rachid and Thomas Henzinger and Vasu Singh}, pages = {321 -- 336}, publisher = {Springer}, title = {{Software transactional memory on relaxed memory models}}, doi = {10.1007/978-3-642-02658-4_26}, volume = {5643}, year = {2009}, } @inproceedings{4385, abstract = {Transactional memories are typically speculative and rely on contention managers to cure conflicts. This paper explores a complementary approach that prevents conflicts by scheduling transactions according to predictions on their access sets. We first explore the theoretical boundaries of this approach and prove that (1) a TM scheduler with an accurate prediction can be 2-competitive with an optimal offline TM scheduler, but (2) even a slight inaccuracy in prediction makes the competitive ratio of the TM scheduler in the order of the number of transactions. We then show that, in practice, there is room for a pragmatic approach with good average case performance. We present Shrink, a scheduler that (1) bases its prediction of transactional accesses on the access patterns of the past transactions from the same thread, and (2) uses a novel heuristic, which we call serialization affinity, to schedule transactions with a probability proportional to the current amount of contention. Shrink obtains roughly 70% accurate read and write access predictions on STMBench7 and STAMP. In our experimental evaluation, Shrink significantly improves STM performance in cases the number of executing threads is higher than the number of available CPU cores. For SwissTM, Shrink improves the performance by up to 55% on STMBench7, and up to 120% on STAMP. For TinySTM, Shrink drastically improves the performance on STMBench7 and STAMP benchmarks.}, author = {Dragojevic, Aleksandar and Guerraoui, Rachid and Singh, Anmol and Singh, Vasu}, booktitle = {Proceedings of the 28th ACM symposium on Principles of distributed computing}, location = {Calgary, Canada}, pages = {7 -- 16}, publisher = {ACM}, title = {{Preventing versus curing: Avoiding conflicts in transactional memories}}, doi = {10.1145/1582716.1582725}, year = {2009}, } @inproceedings{4391, abstract = {We address the problem of analyzing programs such as J2ME midlets for mobile devices, where a central correctness requirement concerns confidentiality of data that the user wants to keep secret. Existing software model checking tools analyze individual program executions, and are not applicable to checking confidentiality properties that require reasoning about equivalence among executions. We develop an automated analysis technique for such properties. We show that both over- and under- approximation is needed for sound analysis. Given a program and a confidentiality requirement, our technique produces a formula that is satisfiable if the requirement holds. We evaluate the approach by analyzing bytecode of a set of Java (J2ME) methods.}, author = {Cerny, Pavol and Alur, Rajeev}, booktitle = {21st International Conference on Computer Aided Verification}, pages = {173 -- 187}, publisher = {Springer}, title = {{Automated analysis of Java methods for confidentiality}}, doi = {10.1007/978-3-642-02658-4_16}, volume = {5643}, year = {2009}, } @inproceedings{4403, abstract = {For programs whose data variables range over boolean or finite domains, program verification is decidable, and this forms the basis of recent tools for software model checking. In this paper, we consider algorithmic verification of programs that use boolean variables, and in addition, access a single read-only array whose length is potentially unbounded, and whose elements range over a potentially unbounded data domain. We show that the reachability problem, while undecidable in general, is (1) Pspace-complete for programs in which the array-accessing for-loops are not nested, (2) decidable for a restricted class of programs with doubly-nested loops. The second result establishes connections to automata and logics defining languages over data words.}, author = {Alur, Rajeev and Cerny, Pavol and Weinstein, Scott}, location = {Coimbra, Portugal}, pages = {86 -- 101}, publisher = {Springer}, title = {{Algorithmic analysis of array-accessing programs}}, doi = {10.1007/978-3-642-04027-6_9}, volume = {5771}, year = {2009}, } @inproceedings{4453, abstract = {We present an on-the-fly abstraction technique for infinite-state continuous -time Markov chains. We consider Markov chains that are specified by a finite set of transition classes. Such models naturally represent biochemical reactions and therefore play an important role in the stochastic modeling of biological systems. We approximate the transient probability distributions at various time instances by solving a sequence of dynamically constructed abstract models, each depending on the previous one. Each abstract model is a finite Markov chain that represents the behavior of the original, infinite chain during a specific time interval. Our approach provides complete information about probability distributions, not just about individual parameters like the mean. The error of each abstraction can be computed, and the precision of the abstraction refined when desired. We implemented the algorithm and demonstrate its usefulness and efficiency on several case studies from systems biology.}, author = {Thomas Henzinger and Maria Mateescu and Wolf, Verena}, pages = {337 -- 352}, publisher = {Springer}, title = {{Sliding-window abstraction for infinite Markov chains}}, doi = {10.1007/978-3-642-02658-4_27}, volume = {5643}, year = {2009}, } @inproceedings{4535, abstract = {Molecular noise, which arises from the randomness of the discrete events in the cell, significantly influences fundamental biological processes. Discrete -state continuous-time stochastic models (CTMC) can be used to describe such effects, but the calculation of the probabilities of certain events is computationally expensive. We present a comparison of two analysis approaches for CTMC. On one hand, we estimate the probabilities of interest using repeated Gillespie simulation and determine the statistical accuracy that we obtain. On the other hand, we apply a numerical reachability analysis that approximates the probability distributions of the system at several time instances. We use examples of cellular processes to demonstrate the superiority of the reachability analysis if accurate results are required.}, author = {Didier, Frédéric and Thomas Henzinger and Maria Mateescu and Wolf, Verena}, pages = {173 -- 188}, publisher = {Springer}, title = {{Approximation of event probabilities in noisy cellular processes}}, doi = {10.1007/978-3-642-03845-7_12}, volume = {5688}, year = {2009}, } @inproceedings{4540, abstract = {Weighted automata are nondeterministic automata with numerical weights on transitions. They can define quantitative languages L that assign to each word w a real number L(w). In the case of infinite words, the value of a run is naturally computed as the maximum, limsup, liminf, limit average, or discounted sum of the transition weights. We study expressiveness and closure questions about these quantitative languages. We first show that the set of words with value greater than a threshold can be non-w-regular for deterministic limit-average and discounted-sum automata, while this set is always w-regular when the threshold is isolated (i.e., some neighborhood around the threshold contains no word). In the latter case, we prove that the w-regular language is robust against small perturbations of the transition weights. We next consider automata with transition weights 0 or 1 and show that they are as expressive as general weighted automata in the limit-average case, but not in the discounted-sum case. Third, for quantitative languages L-1 and L-2, we consider the operations max(L-1, L-2), min(L-1, L-2), and 1-L-1, which generalize the boolean operations on languages, as well as the sum L-1 + L-2. We establish the closure properties of all classes of quantitative languages with respect to these four operations.}, author = {Chatterjee, Krishnendu and Doyen, Laurent and Henzinger, Thomas A}, pages = {199 -- 208}, publisher = {IEEE}, title = {{Expressiveness and closure properties for quantitative languages}}, doi = {10.1109/LICS.2009.16}, year = {2009}, } @inproceedings{4542, abstract = {Weighted automata are finite automata with numerical weights on transitions. Nondeterministic weighted automata define quantitative languages L that assign to each word w a real number L(w) computed as the maximal value of all runs over w, and the value of a run r is a function of the sequence of weights that appear along r. There are several natural functions to consider such as Sup, LimSup, LimInf, limit average, and discounted sum of transition weights. We introduce alternating weighted automata in which the transitions of the runs are chosen by two players in a turn-based fashion. Each word is assigned the maximal value of a run that the first player can enforce regardless of the choices made by the second player. We survey the results about closure properties, expressiveness, and decision problems for nondeterministic weighted automata, and we extend these results to alternating weighted automata. For quantitative languages L 1 and L 2, we consider the pointwise operations max(L 1,L 2), min(L 1,L 2), 1 − L 1, and the sum L 1 + L 2. We establish the closure properties of all classes of alternating weighted automata with respect to these four operations. We next compare the expressive power of the various classes of alternating and nondeterministic weighted automata over infinite words. In particular, for limit average and discounted sum, we show that alternation brings more expressive power than nondeterminism. Finally, we present decidability results and open questions for the quantitative extension of the classical decision problems in automata theory: emptiness, universality, language inclusion, and language equivalence.}, author = {Chatterjee, Krishnendu and Doyen, Laurent and Henzinger, Thomas A}, location = {Wroclaw, Poland}, pages = {3 -- 13}, publisher = {Springer}, title = {{Alternating weighted automata}}, doi = {10.1007/978-3-642-03409-1_2}, volume = {5699}, year = {2009}, } @inproceedings{4543, abstract = {The synthesis of a reactive system with respect to all omega-regular specification requires the solution of a graph game. Such games have been extended in two natural ways. First, a game graph can be equipped with probabilistic choices between alternative transitions, thus allowing the, modeling of uncertain behaviour. These are called stochastic games. Second, a liveness specification can he strengthened to require satisfaction within all unknown but bounded amount of time. These are called finitary objectives. We study. for the first time, the, combination of Stochastic games and finitary objectives. We characterize the requirements on optimal strategies and provide algorithms for Computing the maximal achievable probability of winning stochastic games with finitary parity or Street, objectives. Most notably the set of state's from which a player can win with probability . for a finitary parity objective can he computed in polynomial time even though no polynomial-time algorithm is known in the nonfinitary case.}, author = {Chatterjee, Krishnendu and Henzinger, Thomas A and Horn, Florian}, location = {High Tatras, Slovakia}, pages = {34 -- 54}, publisher = {Springer}, title = {{Stochastic games with finitary objectives}}, doi = {10.1007/978-3-642-03816-7_4}, volume = {5734}, year = {2009}, } @inproceedings{4544, abstract = {We consider concurrent games played on graphs. At every round of a game, each player simultaneously and independently selects a move; the moves jointly determine the transition to a successor state. Two basic objectives are the safety objective to stay forever in a given set of states, and its dual, the reachability objective to reach a given set of states. We present in this paper a strategy improvement algorithm for computing the value of a concurrent safety game, that is, the maximal probability with which player 1 can enforce the safety objective. The algorithm yields a sequence of player-1 strategies which ensure probabilities of winning that converge monotonically to the value of the safety game. Our result is significant because the strategy improvement algorithm provides, for the first time, a way to approximate the value of a concurrent safety game from below. Since a value iteration algorithm, or a strategy improvement algorithm for reachability games, can be used to approximate the same value from above, the combination of both algorithms yields a method for computing a converging sequence of upper and lower bounds for the values of concurrent reachability and safety games. Previous methods could approximate the values of these games only from one direction, and as no rates of convergence are known, they did not provide a practical way to solve these games.}, author = {Krishnendu Chatterjee and de Alfaro, Luca and Thomas Henzinger}, pages = {197 -- 206}, publisher = {SIAM}, title = {{Termination criteria for solving concurrent safety and reachability games}}, doi = {10.1137/1.9781611973068.23}, year = {2009}, } @inproceedings{4545, abstract = {A stochastic game is a two-player game played oil a graph, where in each state the successor is chosen either by One of the players, or according to a probability distribution. We Survey Stochastic games with limsup and liminf objectives. A real-valued re-ward is assigned to each state, and the value of all infinite path is the limsup (resp. liminf) of all rewards along the path. The value of a stochastic game is the maximal expected value of an infinite path that call he achieved by resolving the decisions of the first player. We present the complexity of computing values of Stochastic games and their subclasses, and the complexity, of optimal strategies in such games. }, author = {Chatterjee, Krishnendu and Doyen, Laurent and Henzinger, Thomas A}, location = {Rhodos, Greece}, pages = {1 -- 15}, publisher = {Springer}, title = {{A survey of stochastic games with limsup and liminf objectives}}, doi = {10.1007/978-3-642-02930-1_1}, volume = {5556}, year = {2009}, } @inproceedings{4569, abstract = {Most specification languages express only qualitative constraints. However, among two implementations that satisfy a given specification, one may be preferred to another. For example, if a specification asks that every request is followed by a response, one may prefer an implementation that generates responses quickly but does not generate unnecessary responses. We use quantitative properties to measure the “goodness” of an implementation. Using games with corresponding quantitative objectives, we can synthesize “optimal” implementations, which are preferred among the set of possible implementations that satisfy a given specification. In particular, we show how automata with lexicographic mean-payoff conditions can be used to express many interesting quantitative properties for reactive systems. In this framework, the synthesis of optimal implementations requires the solution of lexicographic mean-payoff games (for safety requirements), and the solution of games with both lexicographic mean-payoff and parity objectives (for liveness requirements). We present algorithms for solving both kinds of novel graph games.}, author = {Bloem, Roderick and Chatterjee, Krishnendu and Henzinger, Thomas A and Jobstmann, Barbara}, location = {Grenoble, France}, pages = {140 -- 156}, publisher = {Springer}, title = {{Better quality in synthesis through quantitative objectives}}, doi = {10.1007/978-3-642-02658-4_14}, volume = {5643}, year = {2009}, } @inproceedings{4580, abstract = {Alpaga is a solver for two-player parity games with imperfect information. Given the description of a game, it determines whether the first player can ensure to win and, if so, it constructs a winning strategy. The tool provides a symbolic implementation of a recent algorithm based on antichains.}, author = {Berwanger, Dietmar and Krishnendu Chatterjee and De Wulf, Martin and Doyen, Laurent and Thomas Henzinger}, pages = {58 -- 61}, publisher = {Springer}, title = {{Alpaga: A tool for solving parity games with imperfect information}}, doi = {10.1007/978-3-642-00768-2_7}, volume = {5505}, year = {2009}, } @article{21514, abstract = {This paper describes observations and metrological analyses made to compare the replication quality of polymeric replicas obtained by filling micro-cavities using both hot embossing and micro-injection moulding processes. The experiments are performed with polypropylene (PP) at a constant melt temperature and a constant mould temperature, whereas hot embossing tests are carried out with the same polymer at temperatures close to the softening one. The results concerning the micro-cavities filling provide information on the reliability about the possibilities of replication topographical surface geometries. The data obtained by scanning mechanical microscopy (SMM) are used to determine the comparative filling ratio values.}, author = {Sahli, M. and Millot, C. and Roques-Carmes, Charles and Khan Malek, C. and Barriere, T. and Gelin, J.C.}, issn = {1873-4774}, journal = {Journal of Materials Processing Technology}, keywords = {Hot embossing, Micro-injection moulding, Micro-cavities replication, Polypropylene polymer, Scanning mechanical microscopy, Roughness parameters}, number = {18-19}, pages = {5851--5861}, publisher = {Elsevier}, title = {{Quality assessment of polymer replication by hot embossing and micro-injection moulding processes using scanning mechanical microscopy}}, doi = {10.1016/j.jmatprotec.2009.06.011}, volume = {209}, year = {2009}, } @article{11878, abstract = {Given only the URL of a web page, can we identify its language? This is the question that we examine in this paper. Such a language classifier is, for example, useful for crawlers of web search engines, which frequently try to satisfy certain language quotas. To determine the language of uncrawled web pages, they have to download the page, which might be wasteful, if the page is not in the desired language. With URL-based language classifiers these redundant downloads can be avoided. We apply a variety of machine learning algorithms to the language identification task and evaluate their performance in extensive experiments for five languages: English, French, German, Spanish and Italian. Our best methods achieve an F-measure, averaged over all languages, of around .90 for both a random sample of 1,260 web page from a large web crawl and for 25k pages from the ODP directory. For 5k pages of web search engine results we even achieve an F-measure of .96. The achieved recall for these collections is .93, .88 and .95 respectively. Two independent human evaluators performed considerably worse on the task, with an F-measure of .75 and a typical recall of a mere .67. Using only country-code top-level domains, such as .de or .fr yields a good precision, but a typical recall of below .60 and an F-measure of around .68.}, author = {Baykan, Eda and Henzinger, Monika H and Weber, Ingmar}, issn = {2150-8097}, journal = {Proceedings of the VLDB Endowment}, number = {1}, pages = {176--187}, publisher = {Association for Computing Machinery}, title = {{Web page language identification based on URLs}}, doi = {10.14778/1453856.1453880}, volume = {1}, year = {2008}, }