@inproceedings{942,
abstract = {A notable class of techniques for automatic program repair is known as semantics-based. Such techniques, e.g., Angelix, infer semantic specifications via symbolic execution, and then use program synthesis to construct new code that satisfies those inferred specifications. However, the obtained specifications are naturally incomplete, leaving the synthesis engine with a difficult task of synthesizing a general solution from a sparse space of many possible solutions that are consistent with the provided specifications but that do not necessarily generalize. We present S3, a new repair synthesis engine that leverages programming-by-examples methodology to synthesize high-quality bug repairs. The novelty in S3 that allows it to tackle the sparse search space to create more general repairs is three-fold: (1) A systematic way to customize and constrain the syntactic search space via a domain-specific language, (2) An efficient enumeration-based search strategy over the constrained search space, and (3) A number of ranking features based on measures of the syntactic and semantic distances between candidate solutions and the original buggy program. We compare S3’s repair effectiveness with state-of-the-art synthesis engines Angelix, Enumerative, and CVC4. S3 can successfully and correctly fix at least three times more bugs than the best baseline on datasets of 52 bugs in small programs, and 100 bugs in real-world large programs. },
author = {Le, Xuan and Chu, Duc Hiep and Lo, David and Le Goues, Claire and Visser, Willem},
isbn = {978-145035105-8},
location = {Paderborn, Germany},
pages = {593 -- 604},
publisher = {ACM},
title = {{S3: Syntax- and semantic-guided repair synthesis via programming by examples}},
doi = {10.1145/3106237.3106309},
volume = {F130154},
year = {2017},
}
@proceedings{638,
editor = {Bogomolov, Sergiy and Martel, Matthieu and Prabhakar, Pavithra},
publisher = {Springer},
title = {{Numerical Software Verification}},
doi = {10.1007/978-3-319-54292-8},
volume = {10152},
year = {2017},
}
@inproceedings{549,
abstract = {Model checking is usually based on a comprehensive traversal of the state space. Causality-based model checking is a radically different approach that instead analyzes the cause-effect relationships in a program. We give an overview on a new class of model checking algorithms that capture the causal relationships in a special data structure called concurrent traces. Concurrent traces identify key events in an execution history and link them through their cause-effect relationships. The model checker builds a tableau of concurrent traces, where the case splits represent different causal explanations of a hypothetical error. Causality-based model checking has been implemented in the ARCTOR tool, and applied to previously intractable multi-threaded benchmarks.},
author = {Finkbeiner, Bernd and Kupriyanov, Andrey},
booktitle = {Electronic Proceedings in Theoretical Computer Science},
issn = {20752180},
location = {Uppsala, Sweden},
pages = {31 -- 38},
publisher = {Open Publishing Association},
title = {{Causality-based model checking}},
doi = {10.4204/EPTCS.259.3},
volume = {259},
year = {2017},
}
@article{467,
abstract = {Recently there has been a significant effort to handle quantitative properties in formal verification and synthesis. While weighted automata over finite and infinite words provide a natural and flexible framework to express quantitative properties, perhaps surprisingly, some basic system properties such as average response time cannot be expressed using weighted automata or in any other known decidable formalism. In this work, we introduce nested weighted automata as a natural extension of weighted automata, which makes it possible to express important quantitative properties such as average response time. In nested weighted automata, a master automaton spins off and collects results from weighted slave automata, each of which computes a quantity along a finite portion of an infinite word. Nested weighted automata can be viewed as the quantitative analogue of monitor automata, which are used in runtime verification. We establish an almost-complete decidability picture for the basic decision problems about nested weighted automata and illustrate their applicability in several domains. In particular, nested weighted automata can be used to decide average response time properties.},
author = {Chatterjee, Krishnendu and Henzinger, Thomas A and Otop, Jan},
issn = {15293785},
journal = {ACM Transactions on Computational Logic (TOCL)},
number = {4},
publisher = {ACM},
title = {{Nested weighted automata}},
doi = {10.1145/3152769},
volume = {18},
year = {2017},
}
@inproceedings{633,
abstract = {A Rapidly-exploring Random Tree (RRT) is an algorithm which can search a non-convex region of space by incrementally building a space-filling tree. The tree is constructed from random points drawn from system’s state space and is biased to grow towards large unexplored areas in the system. RRT can provide better coverage of a system’s possible behaviors compared with random simulations, but is more lightweight than full reachability analysis. In this paper, we explore some of the design decisions encountered while implementing a hybrid extension of the RRT algorithm, which have not been elaborated on before. In particular, we focus on handling non-determinism, which arises due to discrete transitions. We introduce the notion of important points to account for this phenomena. We showcase our ideas using heater and navigation benchmarks.},
author = {Bak, Stanley and Bogomolov, Sergiy and Henzinger, Thomas A and Kumar, Aviral},
editor = {Abate, Alessandro and Bodo, Sylvie},
isbn = {978-331963500-2},
location = {Heidelberg, Germany},
pages = {83 -- 89},
publisher = {Springer},
title = {{Challenges and tool implementation of hybrid rapidly exploring random trees}},
doi = {10.1007/978-3-319-63501-9_6},
volume = {10381},
year = {2017},
}
@inproceedings{950,
abstract = {Two-player games on graphs are widely studied in formal methods as they model the interaction between a system and its environment. The game is played by moving a token throughout a graph to produce an infinite path. There are several common modes to determine how the players move the token through the graph; e.g., in turn-based games the players alternate turns in moving the token. We study the bidding mode of moving the token, which, to the best of our knowledge, has never been studied in infinite-duration games. Both players have separate budgets, which sum up to $1$. In each turn, a bidding takes place. Both players submit bids simultaneously, and a bid is legal if it does not exceed the available budget. The winner of the bidding pays his bid to the other player and moves the token. For reachability objectives, repeated bidding games have been studied and are called Richman games. There, a central question is the existence and computation of threshold budgets; namely, a value t\in [0,1] such that if\PO's budget exceeds $t$, he can win the game, and if\PT's budget exceeds 1-t, he can win the game. We focus on parity games and mean-payoff games. We show the existence of threshold budgets in these games, and reduce the problem of finding them to Richman games. We also determine the strategy-complexity of an optimal strategy. Our most interesting result shows that memoryless strategies suffice for mean-payoff bidding games.
},
author = {Avni, Guy and Henzinger, Thomas A and Chonev, Ventsislav K},
issn = {1868-8969},
location = {Berlin, Germany},
publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
title = {{Infinite-duration bidding games}},
doi = {10.4230/LIPIcs.CONCUR.2017.21},
volume = {85},
year = {2017},
}
@inproceedings{962,
abstract = {We present a new algorithm for model counting of a class of string constraints. In addition to the classic operation of concatenation, our class includes some recursively defined operations such as Kleene closure, and replacement of substrings. Additionally, our class also includes length constraints on the string expressions, which means, by requiring reasoning about numbers, that we face a multi-sorted logic. In the end, our string constraints are motivated by their use in programming for web applications. Our algorithm comprises two novel features: the ability to use a technique of (1) partial derivatives for constraints that are already in a solved form, i.e. a form where its (string) satisfiability is clearly displayed, and (2) non-progression, where cyclic reasoning in the reduction process may be terminated (thus allowing for the algorithm to look elsewhere). Finally, we experimentally compare our model counter with two recent works on model counting of similar constraints, SMC [18] and ABC [5], to demonstrate its superior performance.},
author = {Trinh, Minh and Chu, Duc Hiep and Jaffar, Joxan},
editor = {Majumdar, Rupak and Kunčak, Viktor},
issn = {03029743},
location = {Heidelberg, Germany},
pages = {399 -- 418},
publisher = {Springer},
title = {{Model counting for recursively-defined strings}},
doi = {10.1007/978-3-319-63390-9_21},
volume = {10427},
year = {2017},
}
@inproceedings{711,
abstract = {Nested weighted automata (NWA) present a robust and convenient automata-theoretic formalism for quantitative specifications. Previous works have considered NWA that processed input words only in the forward direction. It is natural to allow the automata to process input words backwards as well, for example, to measure the maximal or average time between a response and the preceding request. We therefore introduce and study bidirectional NWA that can process input words in both directions. First, we show that bidirectional NWA can express interesting quantitative properties that are not expressible by forward-only NWA. Second, for the fundamental decision problems of emptiness and universality, we establish decidability and complexity results for the new framework which match the best-known results for the special case of forward-only NWA. Thus, for NWA, the increased expressiveness of bidirectionality is achieved at no additional computational complexity. This is in stark contrast to the unweighted case, where bidirectional finite automata are no more expressive but exponentially more succinct than their forward-only counterparts.},
author = {Chatterjee, Krishnendu and Henzinger, Thomas A and Otop, Jan},
issn = {18688969},
location = {Berlin, Germany},
publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
title = {{Bidirectional nested weighted automata}},
doi = {10.4230/LIPIcs.CONCUR.2017.5},
volume = {85},
year = {2017},
}
@inproceedings{963,
abstract = {Network games are widely used as a model for selfish resource-allocation problems. In the classical model, each player selects a path connecting her source and target vertex. The cost of traversing an edge depends on the number of players that traverse it. Thus, it abstracts the fact that different users may use a resource at different times and for different durations, which plays an important role in defining the costs of the users in reality. For example, when transmitting packets in a communication network, routing traffic in a road network, or processing a task in a production system, the traversal of the network involves an inherent delay, and so sharing and congestion of resources crucially depends on time. We study timed network games , which add a time component to network games. Each vertex v in the network is associated with a cost function, mapping the load on v to the price that a player pays for staying in v for one time unit with this load. In addition, each edge has a guard, describing time intervals in which the edge can be traversed, forcing the players to spend time on vertices. Unlike earlier work that add a time component to network games, the time in our model is continuous and cannot be discretized. In particular, players have uncountably many strategies, and a game may have uncountably many pure Nash equilibria. We study properties of timed network games with cost-sharing or congestion cost functions: their stability, equilibrium inefficiency, and complexity. In particular, we show that the answer to the question whether we can restrict attention to boundary strategies, namely ones in which edges are traversed only at the boundaries of guards, is mixed. },
author = {Avni, Guy and Guha, Shibashis and Kupferman, Orna},
issn = {18688969},
location = {Aalborg, Denmark},
publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
title = {{Timed network games with clocks}},
doi = {10.4230/LIPIcs.MFCS.2017.37},
volume = {83},
year = {2017},
}
@article{743,
abstract = {This special issue of the Journal on Formal Methods in System Design is dedicated to Prof. Helmut Veith, who unexpectedly passed away in March 2016. Helmut Veith was a brilliant researcher, inspiring collaborator, passionate mentor, generous friend, and valued member of the formal methods community. Helmut was not only known for his numerous and influential contributions in the field of automated verification (most prominently his work on Counterexample-Guided Abstraction Refinement [1,2]), but also for his untiring and passionate efforts for the logic community: he co-organized the Vienna Summer of Logic (an event comprising twelve conferences and numerous workshops which attracted thousands of researchers from all over the world), he initiated the Vienna Center for Logic and Algorithms (which promotes international collaboration on logic and algorithms and organizes outreach events such as the LogicLounge), and he coordinated the Doctoral Program on Logical Methods in Computer Science at TU Wien (currently educating more than 40 doctoral students) and a National Research Network on Rigorous Systems Engineering (uniting fifteen researchers in Austria to address the challenge of building reliable and safe computer
systems). With his enthusiasm and commitment, Helmut completely reshaped the Austrian research landscape in the field of logic and verification in his few years as a full professor at TU Wien.},
author = {Gottlob, Georg and Henzinger, Thomas A and Weißenbacher, Georg},
journal = {Formal Methods in System Design},
number = {2},
pages = {267 -- 269},
publisher = {Springer},
title = {{Preface of the special issue in memoriam Helmut Veith}},
doi = {10.1007/s10703-017-0307-6},
volume = {51},
year = {2017},
}
@article{1196,
abstract = {We define the . model-measuring problem: given a model . M and specification . ϕ, what is the maximal distance . ρ such that all models . M' within distance . ρ from . M satisfy (or violate) . ϕ. The model-measuring problem presupposes a distance function on models. We concentrate on . automatic distance functions, which are defined by weighted automata. The model-measuring problem subsumes several generalizations of the classical model-checking problem, in particular, quantitative model-checking problems that measure the degree of satisfaction of a specification; robustness problems that measure how much a model can be perturbed without violating the specification; and parameter synthesis for hybrid systems. We show that for automatic distance functions, and (a) . ω-regular linear-time, (b) . ω-regular branching-time, and (c) hybrid specifications, the model-measuring problem can be solved.We use automata-theoretic model-checking methods for model measuring, replacing the emptiness question for word, tree, and hybrid automata by the . optimal-value question for the weighted versions of these automata. For automata over words and trees, we consider weighted automata that accumulate weights by maximizing, summing, discounting, and limit averaging. For hybrid automata, we consider monotonic (parametric) hybrid automata, a hybrid counterpart of (discrete) weighted automata.We give several examples of using the model-measuring problem to compute various notions of robustness and quantitative satisfaction for temporal specifications. Further, we propose the modeling framework for model measuring to ease the specification and reduce the likelihood of errors in modeling.Finally, we present a variant of the model-measuring problem, called the . model-repair problem. The model-repair problem applies to models that do not satisfy the specification; it can be used to derive restrictions, under which the model satisfies the specification, i.e., to repair the model.},
author = {Henzinger, Thomas A and Otop, Jan},
journal = {Nonlinear Analysis: Hybrid Systems},
pages = {166 -- 190},
publisher = {Elsevier},
title = {{Model measuring for discrete and hybrid systems}},
doi = {10.1016/j.nahs.2016.09.001},
volume = {23},
year = {2017},
}
@article{471,
abstract = {We present a new algorithm for the statistical model checking of Markov chains with respect to unbounded temporal properties, including full linear temporal logic. The main idea is that we monitor each simulation run on the fly, in order to detect quickly if a bottom strongly connected component is entered with high probability, in which case the simulation run can be terminated early. As a result, our simulation runs are often much shorter than required by termination bounds that are computed a priori for a desired level of confidence on a large state space. In comparison to previous algorithms for statistical model checking our method is not only faster in many cases but also requires less information about the system, namely, only the minimum transition probability that occurs in the Markov chain. In addition, our method can be generalised to unbounded quantitative properties such as mean-payoff bounds. },
author = {Daca, Przemyslaw and Henzinger, Thomas A and Kretinsky, Jan and Petrov, Tatjana},
issn = {15293785},
journal = {ACM Transactions on Computational Logic (TOCL)},
number = {2},
publisher = {ACM},
title = {{Faster statistical model checking for unbounded temporal properties}},
doi = {10.1145/3060139},
volume = {18},
year = {2017},
}
@inproceedings{647,
abstract = {Despite researchers’ efforts in the last couple of decades, reachability analysis is still a challenging problem even for linear hybrid systems. Among the existing approaches, the most practical ones are mainly based on bounded-time reachable set over-approximations. For the purpose of unbounded-time analysis, one important strategy is to abstract the original system and find an invariant for the abstraction. In this paper, we propose an approach to constructing a new kind of abstraction called conic abstraction for affine hybrid systems, and to computing reachable sets based on this abstraction. The essential feature of a conic abstraction is that it partitions the state space of a system into a set of convex polyhedral cones which is derived from a uniform conic partition of the derivative space. Such a set of polyhedral cones is able to cut all trajectories of the system into almost straight segments so that every segment of a reach pipe in a polyhedral cone tends to be straight as well, and hence can be over-approximated tightly by polyhedra using similar techniques as HyTech or PHAVer. In particular, for diagonalizable affine systems, our approach can guarantee to find an invariant for unbounded reachable sets, which is beyond the capability of bounded-time reachability analysis tools. We implemented the approach in a tool and experiments on benchmarks show that our approach is more powerful than SpaceEx and PHAVer in dealing with diagonalizable systems.},
author = {Bogomolov, Sergiy and Giacobbe, Mirco and Henzinger, Thomas A and Kong, Hui},
isbn = {978-331965764-6},
location = {Berlin, Germany},
pages = {116 -- 132},
publisher = {Springer},
title = {{Conic abstractions for hybrid systems}},
doi = {10.1007/978-3-319-65765-3_7},
volume = {10419 },
year = {2017},
}
@inproceedings{1135,
abstract = {Time-triggered (TT) switched networks are a deterministic communication infrastructure used by real-time distributed embedded systems. These networks rely on the notion of globally discretized time (i.e. time slots) and a static TT schedule that prescribes which message is sent through which link at every time slot, such that all messages reach their destination before a global timeout. These schedules are generated offline, assuming a static network with fault-free links, and entrusting all error-handling functions to the end user. Assuming the network is static is an over-optimistic view, and indeed links tend to fail in practice. We study synthesis of TT schedules on a network in which links fail over time and we assume the switches run a very simple error-recovery protocol once they detect a crashed link. We address the problem of finding a pk; qresistant schedule; namely, one that, assuming the switches run a fixed error-recovery protocol, guarantees that the number of messages that arrive at their destination by the timeout is at least no matter what sequence of at most k links fail. Thus, we maintain the simplicity of the switches while giving a guarantee on the number of messages that meet the timeout. We show how a pk; q-resistant schedule can be obtained using a CEGAR-like approach: find a schedule, decide whether it is pk; q-resistant, and if it is not, use the witnessing fault sequence to generate a constraint that is added to the program. The newly added constraint disallows the schedule to be regenerated in a future iteration while also eliminating several other schedules that are not pk; q-resistant. We illustrate the applicability of our approach using an SMT-based implementation. © 2016 ACM.},
author = {Avni, Guy and Guha, Shibashis and Rodríguez Navas, Guillermo},
booktitle = {Proceedings of the 13th International Conference on Embedded Software },
location = {Pittsburgh, PA, USA},
publisher = {ACM},
title = {{Synthesizing time triggered schedules for switched networks with faulty links}},
doi = {10.1145/2968478.2968499},
year = {2016},
}
@inproceedings{1205,
abstract = {In this paper, we present a formal model-driven engineering approach to establishing a safety-assured implementation of Multifunction vehicle bus controller (MVBC) based on the generic reference models and requirements described in the International Electrotechnical Commission (IEC) standard IEC-61375. First, the generic models described in IEC-61375 are translated into a network of timed automata, and some safety requirements tested in IEC-61375 are formalized as timed computation tree logic (TCTL) formulas. With the help of Uppaal, we check and debug whether the timed automata satisfy the formulas or not. Within this step, several logic inconsistencies in the original standard are detected and corrected. Then, we apply the tool Times to generate C code from the verified model, which was later synthesized into a real MVBC chip. Finally, the runtime verification tool RMOR is applied to verify some safety requirements at the implementation level. We set up a real platform with worldwide mostly used MVBC D113, and verify the correctness and the scalability of the synthesized MVBC chip more comprehensively. The errors in the standard has been confirmed and the resulted MVBC has been deployed in real train communication network.},
author = {Jiang, Yu and Liu, Han and Song, Houbing and Kong, Hui and Gu, Ming and Sun, Jiaguang and Sha, Lui},
location = {Limassol, Cyprus},
pages = {757 -- 763},
publisher = {Springer},
title = {{Safety assured formal model driven design of the multifunction vehicle bus controller}},
doi = {10.1007/978-3-319-48989-6_47},
volume = {9995},
year = {2016},
}
@inproceedings{1166,
abstract = {POMDPs are standard models for probabilistic planning problems, where an agent interacts with an uncertain environment. We study the problem of almost-sure reachability, where given a set of target states, the question is to decide whether there is a policy to ensure that the target set is reached with probability 1 (almost-surely). While in general the problem is EXPTIMEcomplete, in many practical cases policies with a small amount of memory suffice. Moreover, the existing solution to the problem is explicit, which first requires to construct explicitly an exponential reduction to a belief-support MDP. In this work, we first study the existence of observation-stationary strategies, which is NP-complete, and then small-memory strategies. We present a symbolic algorithm by an efficient encoding to SAT and using a SAT solver for the problem. We report experimental results demonstrating the scalability of our symbolic (SAT-based) approach. © 2016, Association for the Advancement of Artificial Intelligence (www.aaai.org). All rights reserved.},
author = {Chatterjee, Krishnendu and Chmelik, Martin and Davies, Jessica},
booktitle = {Proceedings of the Thirtieth AAAI Conference on Artificial Intelligence},
location = {Phoenix, AZ, USA},
pages = {3225 -- 3232},
publisher = {AAAI Press},
title = {{A symbolic SAT based algorithm for almost sure reachability with small strategies in pomdps}},
volume = {2016},
year = {2016},
}
@inproceedings{1421,
abstract = {Hybridization methods enable the analysis of hybrid automata with complex, nonlinear dynamics through a sound abstraction process. Complex dynamics are converted to simpler ones with added noise, and then analysis is done using a reachability method for the simpler dynamics. Several such recent approaches advocate that only "dynamic" hybridization techniquesi.e., those where the dynamics are abstracted on-The-fly during a reachability computation are effective. In this paper, we demonstrate this is not the case, and create static hybridization methods that are more scalable than earlier approaches. The main insight in our approach is that quick, numeric simulations can be used to guide the process, eliminating the need for an exponential number of hybridization domains. Transitions between domains are generally timetriggered, avoiding accumulated error from geometric intersections. We enhance our static technique by combining time-Triggered transitions with occasional space-Triggered transitions, and demonstrate the benefits of the combined approach in what we call mixed-Triggered hybridization. Finally, error modes are inserted to confirm that the reachable states stay within the hybridized regions. The developed techniques can scale to higher dimensions than previous static approaches, while enabling the parallelization of the main performance bottleneck for many dynamic hybridization approaches: The nonlinear optimization required for sound dynamics abstraction. We implement our method as a model transformation pass in the HYST tool, and perform reachability analysis and evaluation using an unmodified version of SpaceEx on nonlinear models with up to six dimensions.},
author = {Bak, Stanley and Bogomolov, Sergiy and Henzinger, Thomas A and Johnson, Taylor and Prakash, Pradyot},
location = {Vienna, Austria},
pages = {155 -- 164},
publisher = {Springer},
title = {{Scalable static hybridization methods for analysis of nonlinear systems}},
doi = {10.1145/2883817.2883837},
year = {2016},
}
@article{1705,
abstract = {Hybrid systems represent an important and powerful formalism for modeling real-world applications such as embedded systems. A verification tool like SpaceEx is based on the exploration of a symbolic search space (the region space). As a verification tool, it is typically optimized towards proving the absence of errors. In some settings, e.g., when the verification tool is employed in a feedback-directed design cycle, one would like to have the option to call a version that is optimized towards finding an error trajectory in the region space. A recent approach in this direction is based on guided search. Guided search relies on a cost function that indicates which states are promising to be explored, and preferably explores more promising states first. In this paper, we propose an abstraction-based cost function based on coarse-grained space abstractions for guiding the reachability analysis. For this purpose, a suitable abstraction technique that exploits the flexible granularity of modern reachability analysis algorithms is introduced. The new cost function is an effective extension of pattern database approaches that have been successfully applied in other areas. The approach has been implemented in the SpaceEx model checker. The evaluation shows its practical potential.},
author = {Bogomolov, Sergiy and Donzé, Alexandre and Frehse, Goran and Grosu, Radu and Johnson, Taylor and Ladan, Hamed and Podelski, Andreas and Wehrle, Martin},
journal = {International Journal on Software Tools for Technology Transfer},
number = {4},
pages = {449 -- 467},
publisher = {Springer},
title = {{Guided search for hybrid systems based on coarse-grained space abstractions}},
doi = {10.1007/s10009-015-0393-y},
volume = {18},
year = {2016},
}
@phdthesis{1130,
abstract = {In this thesis we present a computer-aided programming approach to concurrency. Our approach
helps the programmer by automatically fixing concurrency-related bugs, i.e. bugs that occur
when the program is executed using an aggressive preemptive scheduler, but not when using a
non-preemptive (cooperative) scheduler. Bugs are program behaviours that are incorrect w.r.t.
a specification. We consider both user-provided explicit specifications in the form of assertion
statements in the code as well as an implicit specification. The implicit specification is inferred
from the non-preemptive behaviour. Let us consider sequences of calls that the program makes
to an external interface. The implicit specification requires that any such sequence produced
under a preemptive scheduler should be included in the set of sequences produced under a
non-preemptive scheduler.
We consider several semantics-preserving fixes that go beyond atomic sections typically
explored in the synchronisation synthesis literature. Our synthesis is able to place locks, barriers
and wait-signal statements and last, but not least reorder independent statements. The latter
may be useful if a thread is released to early, e.g., before some initialisation is completed. We
guarantee that our synthesis does not introduce deadlocks and that the synchronisation inserted
is optimal w.r.t. a given objective function.
We dub our solution trace-based synchronisation synthesis and it is loosely based on
counterexample-guided inductive synthesis (CEGIS). The synthesis works by discovering a
trace that is incorrect w.r.t. the specification and identifying ordering constraints crucial to trigger
the specification violation. Synchronisation may be placed immediately (greedy approach) or
delayed until all incorrect traces are found (non-greedy approach). For the non-greedy approach
we construct a set of global constraints over synchronisation placements. Each model of the
global constraints set corresponds to a correctness-ensuring synchronisation placement. The
placement that is optimal w.r.t. the given objective function is chosen as the synchronisation
solution.
We evaluate our approach on a number of realistic (albeit simplified) Linux device-driver
benchmarks. The benchmarks are versions of the drivers with known concurrency-related bugs.
For the experiments with an explicit specification we added assertions that would detect the bugs
in the experiments. Device drivers lend themselves to implicit specification, where the device and
the operating system are the external interfaces. Our experiments demonstrate that our synthesis
method is precise and efficient. We implemented objective functions for coarse-grained and
fine-grained locking and observed that different synchronisation placements are produced for
our experiments, favouring e.g. a minimal number of synchronisation operations or maximum
concurrency.},
author = {Tarrach, Thorsten},
pages = {151},
publisher = {IST Austria},
title = {{Automatic synthesis of synchronisation primitives for concurrent programs}},
year = {2016},
}
@inproceedings{1256,
abstract = {Simulink is widely used for model driven development (MDD) of industrial software systems. Typically, the Simulink based development is initiated from Stateflow modeling, followed by simulation, validation and code generation mapped to physical execution platforms. However, recent industrial trends have raised the demands of rigorous verification on safety-critical applications, which is unfortunately challenging for Simulink. In this paper, we present an approach to bridge the Stateflow based model driven development and a well- defined rigorous verification. First, we develop a self- contained toolkit to translate Stateflow model into timed automata, where major advanced modeling features in Stateflow are supported. Taking advantage of the strong verification capability of Uppaal, we can not only find bugs in Stateflow models which are missed by Simulink Design Verifier, but also check more important temporal properties. Next, we customize a runtime verifier for the generated nonintrusive VHDL and C code of Stateflow model for monitoring. The major strength of the customization is the flexibility to collect and analyze runtime properties with a pure software monitor, which opens more opportunities for engineers to achieve high reliability of the target system compared with the traditional act that only relies on Simulink Polyspace. We incorporate these two parts into original Stateflow based MDD seamlessly. In this way, safety-critical properties are both verified at the model level, and at the consistent system implementation level with physical execution environment in consideration. We apply our approach on a train controller design, and the verified implementation is tested and deployed on a real hardware platform.},
author = {Jiang, Yu and Yang, Yixiao and Liu, Han and Kong, Hui and Gu, Ming and Sun, Jiaguang and Sha, Lui},
location = {Vienna, Austria},
publisher = {IEEE},
title = {{From stateflow simulation to verified implementation: A verification approach and a real-time train controller design}},
doi = {10.1109/RTAS.2016.7461337},
year = {2016},
}
@inproceedings{1390,
abstract = {The goal of automatic program repair is to identify a set of syntactic changes that can turn a program that is incorrect with respect
to a given specification into a correct one. Existing program repair techniques typically aim to find any program that meets the given specification. Such “best-effort” strategies can end up generating a program that is quite different from the original one. Novel techniques have been proposed to compute syntactically minimal program fixes, but the smallest syntactic fix to a program can still significantly alter the original program’s behaviour. We propose a new approach to program repair based on program distances, which can quantify changes not only to the program syntax but also to the program semantics. We call this the quantitative program repair problem where the “optimal” repair is derived using multiple distances. We implement a solution to the quantitative repair
problem in a prototype tool called Qlose
(Quantitatively close), using the program synthesizer Sketch. We evaluate the effectiveness of different distances in obtaining desirable repairs by evaluating
Qlose on programs taken from educational tools such as CodeHunt and edX.},
author = {D'Antoni, Loris and Samanta, Roopsha and Singh, Rishabh},
location = {Toronto, Canada},
pages = {383 -- 401},
publisher = {Springer},
title = {{QLOSE: Program repair with quantitative objectives}},
doi = {10.1007/978-3-319-41540-6_21},
volume = {9780},
year = {2016},
}
@inproceedings{1439,
abstract = {Fault-tolerant distributed algorithms play an important role in many critical/high-availability applications. These algorithms are notoriously difficult to implement correctly, due to asynchronous communication and the occurrence of faults, such as the network dropping messages or computers crashing. We introduce PSYNC, a domain specific language based on the Heard-Of model, which views asynchronous faulty systems as synchronous ones with an adversarial environment that simulates asynchrony and faults by dropping messages. We define a runtime system for PSYNC that efficiently executes on asynchronous networks. We formalize the relation between the runtime system and PSYNC in terms of observational refinement. The high-level lockstep abstraction introduced by PSYNC simplifies the design and implementation of fault-tolerant distributed algorithms and enables automated formal verification. We have implemented an embedding of PSYNC in the SCALA programming language with a runtime system for asynchronous networks. We show the applicability of PSYNC by implementing several important fault-tolerant distributed algorithms and we compare the implementation of consensus algorithms in PSYNC against implementations in other languages in terms of code size, runtime efficiency, and verification.},
author = {Dragoi, Cezara and Henzinger, Thomas A and Zufferey, Damien},
location = {St. Petersburg, FL, USA},
pages = {400 -- 415},
publisher = {ACM},
title = {{PSYNC: A partially synchronous language for fault-tolerant distributed algorithms}},
doi = {10.1145/2837614.2837650},
volume = {20-22},
year = {2016},
}
@article{1148,
abstract = {Continuous-time Markov chain (CTMC) models have become a central tool for understanding the dynamics of complex reaction networks and the importance of stochasticity in the underlying biochemical processes. When such models are employed to answer questions in applications, in order to ensure that the model provides a sufficiently accurate representation of the real system, it is of vital importance that the model parameters are inferred from real measured data. This, however, is often a formidable task and all of the existing methods fail in one case or the other, usually because the underlying CTMC model is high-dimensional and computationally difficult to analyze. The parameter inference methods that tend to scale best in the dimension of the CTMC are based on so-called moment closure approximations. However, there exists a large number of different moment closure approximations and it is typically hard to say a priori which of the approximations is the most suitable for the inference procedure. Here, we propose a moment-based parameter inference method that automatically chooses the most appropriate moment closure method. Accordingly, contrary to existing methods, the user is not required to be experienced in moment closure techniques. In addition to that, our method adaptively changes the approximation during the parameter inference to ensure that always the best approximation is used, even in cases where different approximations are best in different regions of the parameter space. © 2016 Elsevier Ireland Ltd},
author = {Schilling, Christian and Bogomolov, Sergiy and Henzinger, Thomas A and Podelski, Andreas and Ruess, Jakob},
journal = {Biosystems},
pages = {15 -- 25},
publisher = {Elsevier},
title = {{Adaptive moment closure for parameter inference of biochemical reaction networks}},
doi = {10.1016/j.biosystems.2016.07.005},
volume = {149},
year = {2016},
}
@inproceedings{1524,
abstract = {When designing genetic circuits, the typical primitives used in major existing modelling formalisms are gene interaction graphs, where edges between genes denote either an activation or inhibition relation. However, when designing experiments, it is important to be precise about the low-level mechanistic details as to how each such relation is implemented. The rule-based modelling language Kappa allows to unambiguously specify mechanistic details such as DNA binding sites, dimerisation of transcription factors, or co-operative interactions. Such a detailed description comes with complexity and computationally costly executions. We propose a general method for automatically transforming a rule-based program, by eliminating intermediate species and adjusting the rate constants accordingly. To the best of our knowledge, we show the first automated reduction of rule-based models based on equilibrium approximations.
Our algorithm is an adaptation of an existing algorithm, which was designed for reducing reaction-based programs; our version of the algorithm scans the rule-based Kappa model in search for those interaction patterns known to be amenable to equilibrium approximations (e.g. Michaelis-Menten scheme). Additional checks are then performed in order to verify if the reduction is meaningful in the context of the full model. The reduced model is efficiently obtained by static inspection over the rule-set. The tool is tested on a detailed rule-based model of a λ-phage switch, which lists 92 rules and 13 agents. The reduced model has 11 rules and 5 agents, and provides a dramatic reduction in simulation time of several orders of magnitude.},
author = {Beica, Andreea and Guet, Calin C and Petrov, Tatjana},
location = {Madrid, Spain},
pages = {173 -- 191},
publisher = {Springer},
title = {{Efficient reduction of kappa models by static inspection of the rule-set}},
doi = {10.1007/978-3-319-26916-0_10},
volume = {9271},
year = {2016},
}
@inproceedings{479,
abstract = {Clinical guidelines and decision support systems (DSS) play an important role in daily practices of medicine. Many text-based guidelines have been encoded for work-flow simulation of DSS to automate health care. During the collaboration with Carle hospital to develop a DSS, we identify that, for some complex and life-critical diseases, it is highly desirable to automatically rigorously verify some complex temporal properties in guidelines, which brings new challenges to current simulation based DSS with limited support of automatical formal verification and real-time data analysis. In this paper, we conduct the first study on applying runtime verification to cooperate with current DSS based on real-time data. Within the proposed technique, a user-friendly domain specific language, named DRTV, is designed to specify vital real-time data sampled by medical devices and temporal properties originated from clinical guidelines. Some interfaces are developed for data acquisition and communication. Then, for medical practice scenarios described in DRTV model, we will automatically generate event sequences and runtime property verifier automata. If a temporal property violates, real-time warnings will be produced by the formal verifier and passed to medical DSS. We have used DRTV to specify different kinds of medical care scenarios, and applied the proposed technique to assist existing DSS. As presented in experiment results, in terms of warning detection, it outperforms the only use of DSS or human inspection, and improves the quality of clinical health care of hospital},
author = {Jiang, Yu and Liu, Han and Kong, Hui and Wang, Rui and Hosseini, Mohamad and Sun, Jiaguang and Sha, Lui},
booktitle = {Proceedings of the 38th International Conference on Software Engineering Companion },
location = {Austin, TX, USA},
pages = {112 -- 121},
publisher = {IEEE},
title = {{Use runtime verification to improve the quality of medical care practice}},
doi = {10.1145/2889160.2889233},
year = {2016},
}
@inproceedings{1093,
abstract = {We introduce a general class of distances (metrics) between Markov chains, which are based on linear behaviour. This class encompasses distances given topologically (such as the total variation distance or trace distance) as well as by temporal logics or automata. We investigate which of the distances can be approximated by observing the systems, i.e. by black-box testing or simulation, and we provide both negative and positive results. },
author = {Daca, Przemyslaw and Henzinger, Thomas A and Kretinsky, Jan and Petrov, Tatjana},
location = {Quebec City; Canada},
publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
title = {{Linear distances between Markov chains}},
doi = {10.4230/LIPIcs.CONCUR.2016.20},
volume = {59},
year = {2016},
}
@inproceedings{1391,
abstract = {We present an extension to the quantifier-free theory of integer arrays which allows us to express counting. The properties expressible in Array Folds Logic (AFL) include statements such as "the first array cell contains the array length," and "the array contains equally many minimal and maximal elements." These properties cannot be expressed in quantified fragments of the theory of arrays, nor in the theory of concatenation. Using reduction to counter machines, we show that the satisfiability problem of AFL is PSPACE-complete, and with a natural restriction the complexity decreases to NP. We also show that adding either universal quantifiers or concatenation leads to undecidability.
AFL contains terms that fold a function over an array. We demonstrate that folding, a well-known concept from functional languages, allows us to concisely summarize loops that count over arrays, which occurs frequently in real-life programs. We provide a tool that can discharge proof obligations in AFL, and we demonstrate on practical examples that our decision procedure can solve a broad range of problems in symbolic testing and program verification.},
author = {Daca, Przemyslaw and Henzinger, Thomas A and Kupriyanov, Andrey},
location = {Toronto, Canada},
pages = {230 -- 248},
publisher = {Springer},
title = {{Array folds logic}},
doi = {10.1007/978-3-319-41540-6_13},
volume = {9780},
year = {2016},
}
@inproceedings{1341,
abstract = {In resource allocation games, selfish players share resources that are needed in order to fulfill their objectives. The cost of using a resource depends on the load on it. In the traditional setting, the players make their choices concurrently and in one-shot. That is, a strategy for a player is a subset of the resources. We introduce and study dynamic resource allocation games. In this setting, the game proceeds in phases. In each phase each player chooses one resource. A scheduler dictates the order in which the players proceed in a phase, possibly scheduling several players to proceed concurrently. The game ends when each player has collected a set of resources that fulfills his objective. The cost for each player then depends on this set as well as on the load on the resources in it – we consider both congestion and cost-sharing games. We argue that the dynamic setting is the suitable setting for many applications in practice. We study the stability of dynamic resource allocation games, where the appropriate notion of stability is that of subgame perfect equilibrium, study the inefficiency incurred due to selfish behavior, and also study problems that are particular to the dynamic setting, like constraints on the order in which resources can be chosen or the problem of finding a scheduler that achieves stability.},
author = {Avni, Guy and Henzinger, Thomas A and Kupferman, Orna},
location = {Liverpool, United Kingdom},
pages = {153 -- 166},
publisher = {Springer},
title = {{Dynamic resource allocation games}},
doi = {10.1007/978-3-662-53354-3_13},
volume = {9928},
year = {2016},
}
@inproceedings{1138,
abstract = {Automata with monitor counters, where the transitions do not depend on counter values, and nested weighted automata are two expressive automata-theoretic frameworks for quantitative properties. For a well-studied and wide class of quantitative functions, we establish that automata with monitor counters and nested weighted automata are equivalent. We study for the first time such quantitative automata under probabilistic semantics. We show that several problems that are undecidable for the classical questions of emptiness and universality become decidable under the probabilistic semantics. We present a complete picture of decidability for such automata, and even an almost-complete picture of computational complexity, for the probabilistic questions we consider. © 2016 ACM.},
author = {Chatterjee, Krishnendu and Henzinger, Thomas A and Otop, Jan},
booktitle = {Proceedings of the 31st Annual ACM/IEEE Symposium},
location = {New York, NY, USA},
pages = {76 -- 85},
publisher = {IEEE},
title = {{Quantitative automata under probabilistic semantics}},
doi = {10.1145/2933575.2933588},
year = {2016},
}
@inproceedings{1227,
abstract = {Many biological systems can be modeled as multiaffine hybrid systems. Due to the nonlinearity of multiaffine systems, it is difficult to verify their properties of interest directly. A common strategy to tackle this problem is to construct and analyze a discrete overapproximation of the original system. However, the conservativeness of a discrete abstraction significantly determines the level of confidence we can have in the properties of the original system. In this paper, in order to reduce the conservativeness of a discrete abstraction, we propose a new method based on a sufficient and necessary decision condition for computing discrete transitions between states in the abstract system. We assume the state space partition of a multiaffine system to be based on a set of multivariate polynomials. Hence, a rectangular partition defined in terms of polynomials of the form (xi − c) is just a simple case of multivariate polynomial partition, and the new decision condition applies naturally. We analyze and demonstrate the improvement of our method over the existing methods using some examples.},
author = {Kong, Hui and Bartocci, Ezio and Bogomolov, Sergiy and Grosu, Radu and Henzinger, Thomas A and Jiang, Yu and Schilling, Christian},
location = {Grenoble, France},
pages = {128 -- 144},
publisher = {Springer},
title = {{Discrete abstraction of multiaffine systems}},
doi = {10.1007/978-3-319-47151-8_9},
volume = {9957},
year = {2016},
}
@inproceedings{1335,
abstract = {In this paper we review various automata-theoretic formalisms for expressing quantitative properties. We start with finite-state Boolean automata that express the traditional regular properties. We then consider weighted ω-automata that can measure the average density of events, which finite-state Boolean automata cannot. However, even weighted ω-automata cannot express basic performance properties like average response time. We finally consider two formalisms of weighted ω-automata with monitors, where the monitors are either (a) counters or (b) weighted automata themselves. We present a translation result to establish that these two formalisms are equivalent. Weighted ω-automata with monitors generalize weighted ω-automata, and can express average response time property. They present a natural, robust, and expressive framework for quantitative specifications, with important decidable properties.},
author = {Chatterjee, Krishnendu and Henzinger, Thomas A and Otop, Jan},
location = {Edinburgh, United Kingdom},
pages = {23 -- 38},
publisher = {Springer},
title = {{Quantitative monitor automata}},
doi = {10.1007/978-3-662-53413-7_2},
volume = {9837},
year = {2016},
}
@inproceedings{1234,
abstract = {We present a new algorithm for the statistical model checking of Markov chains with respect to unbounded temporal properties, including full linear temporal logic. The main idea is that we monitor each simulation run on the fly, in order to detect quickly if a bottom strongly connected component is entered with high probability, in which case the simulation run can be terminated early. As a result, our simulation runs are often much shorter than required by termination bounds that are computed a priori for a desired level of confidence on a large state space. In comparison to previous algorithms for statistical model checking our method is not only faster in many cases but also requires less information about the system, namely, only the minimum transition probability that occurs in the Markov chain. In addition, our method can be generalised to unbounded quantitative properties such as mean-payoff bounds.},
author = {Daca, Przemyslaw and Henzinger, Thomas A and Kretinsky, Jan and Petrov, Tatjana},
location = {Eindhoven, The Netherlands},
pages = {112 -- 129},
publisher = {Springer},
title = {{Faster statistical model checking for unbounded temporal properties}},
doi = {10.1007/978-3-662-49674-9_7},
volume = {9636},
year = {2016},
}
@inproceedings{1134,
abstract = {Hybrid systems have both continuous and discrete dynamics and are useful for modeling a variety of control systems, from air traffic control protocols to robotic maneuvers and beyond. Recently, numerous powerful and scalable tools for analyzing hybrid systems have emerged. Several of these tools implement automated formal methods for mathematically proving a system meets a specification. This tutorial session will present three recent hybrid systems tools: C2E2, HyST, and TuLiP. C2E2 is a simulated-based verification tool for hybrid systems, and uses validated numerical solvers and bloating of simulation traces to verify systems meet specifications. HyST is a hybrid systems model transformation and translation tool, and uses a canonical intermediate representation to support most of the recent verification tools, as well as automated sound abstractions that simplify verification of a given hybrid system. TuLiP is a controller synthesis tool for hybrid systems, where given a temporal logic specification to be satisfied for a system (plant) model, TuLiP will find a controller that meets a given specification. © 2016 IEEE.},
author = {Duggirala, Parasara and Fan, Chuchu and Potok, Matthew and Qi, Bolun and Mitra, Sayan and Viswanathan, Mahesh and Bak, Stanley and Bogomolov, Sergiy and Johnson, Taylor and Nguyen, Luan and Schilling, Christian and Sogokon, Andrew and Tran, Hoang and Xiang, Weiming},
booktitle = {2016 IEEE Conference on Control Applications},
location = {Buenos Aires, Argentina },
publisher = {IEEE},
title = {{Tutorial: Software tools for hybrid systems verification transformation and synthesis C2E2 HyST and TuLiP}},
doi = {10.1109/CCA.2016.7587948},
year = {2016},
}
@inproceedings{1090,
abstract = { While weighted automata provide a natural framework to express quantitative properties, many basic properties like average response time cannot be expressed with weighted automata. Nested weighted automata extend weighted automata and consist of a master automaton and a set of slave automata that are invoked by the master automaton. Nested weighted automata are strictly more expressive than weighted automata (e.g., average response time can be expressed with nested weighted automata), but the basic decision questions have higher complexity (e.g., for deterministic automata, the emptiness question for nested weighted automata is PSPACE-hard, whereas the corresponding complexity for weighted automata is PTIME). We consider a natural subclass of nested weighted automata where at any point at most a bounded number k of slave automata can be active. We focus on automata whose master value function is the limit average. We show that these nested weighted automata with bounded width are strictly more expressive than weighted automata (e.g., average response time with no overlapping requests can be expressed with bound k=1, but not with non-nested weighted automata). We show that the complexity of the basic decision problems (i.e., emptiness and universality) for the subclass with k constant matches the complexity for weighted automata. Moreover, when k is part of the input given in unary we establish PSPACE-completeness.},
author = {Chatterjee, Krishnendu and Henzinger, Thomas A and Otop, Jan},
location = {Krakow; Poland},
publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
title = {{Nested weighted limit-average automata of bounded width}},
doi = {10.4230/LIPIcs.MFCS.2016.24},
volume = {58},
year = {2016},
}
@inproceedings{1095,
abstract = { The semantics of concurrent data structures is usually given by a sequential specification and a consistency condition. Linearizability is the most popular consistency condition due to its simplicity and general applicability. Nevertheless, for applications that do not require all guarantees offered by linearizability, recent research has focused on improving performance and scalability of concurrent data structures by relaxing their semantics. In this paper, we present local linearizability, a relaxed consistency condition that is applicable to container-type concurrent data structures like pools, queues, and stacks. While linearizability requires that the effect of each operation is observed by all threads at the same time, local linearizability only requires that for each thread T, the effects of its local insertion operations and the effects of those removal operations that remove values inserted by T are observed by all threads at the same time. We investigate theoretical and practical properties of local linearizability and its relationship to many existing consistency conditions. We present a generic implementation method for locally linearizable data structures that uses existing linearizable data structures as building blocks. Our implementations show performance and scalability improvements over the original building blocks and outperform the fastest existing container-type implementations. },
author = {Haas, Andreas and Henzinger, Thomas A and Holzer, Andreas and Kirsch, Christoph and Lippautz, Michael and Payer, Hannes and Sezgin, Ali and Sokolova, Ana and Veith, Helmut},
booktitle = {Leibniz International Proceedings in Informatics},
location = {Quebec City; Canada},
publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik},
title = {{Local linearizability for concurrent container-type data structures}},
doi = {10.4230/LIPIcs.CONCUR.2016.6},
volume = {59},
year = {2016},
}
@inproceedings{1103,
abstract = {We propose two parallel state-space-exploration algorithms for hybrid automaton (HA), with the goal of enhancing performance on multi-core shared-memory systems. The first uses the parallel, breadth-first-search algorithm (PBFS) of the SPIN model checker, when traversing the discrete modes of the HA, and enhances it with a parallel exploration of the continuous states within each mode. We show that this simple-minded extension of PBFS does not provide the desired load balancing in many HA benchmarks. The second algorithm is a task-parallel BFS algorithm (TP-BFS), which uses a cheap precomputation of the cost associated with the post operations (both continuous and discrete) in order to improve load balancing. We illustrate the TP-BFS and the cost precomputation of the post operators on a support-function-based algorithm for state-space exploration. The performance comparison of the two algorithms shows that, in general, TP-BFS provides a better utilization/load-balancing of the CPU. Both algorithms are implemented in the model checker XSpeed. Our experiments show a maximum speed-up of more than 2000 χ on a navigation benchmark, with respect to SpaceEx LGG scenario. In order to make the comparison fair, we employed an equal number of post operations in both tools. To the best of our knowledge, this paper represents the first attempt to provide parallel, reachability-analysis algorithms for HA.},
author = {Gurung, Amit and Deka, Arup and Bartocci, Ezio and Bogomolov, Sergiy and Grosu, Radu and Ray, Rajarshi},
location = {Kanpur, India },
publisher = {IEEE},
title = {{Parallel reachability analysis for hybrid systems}},
doi = {10.1109/MEMCOD.2016.7797741},
year = {2016},
}
@inproceedings{1230,
abstract = {Concolic testing is a promising method for generating test suites for large programs. However, it suffers from the path-explosion problem and often fails to find tests that cover difficult-to-reach parts of programs. In contrast, model checkers based on counterexample-guided abstraction refinement explore programs exhaustively, while failing to scale on large programs with precision. In this paper, we present a novel method that iteratively combines concolic testing and model checking to find a test suite for a given coverage criterion. If concolic testing fails to cover some test goals, then the model checker refines its program abstraction to prove more paths infeasible, which reduces the search space for concolic testing. We have implemented our method on top of the concolictesting tool Crest and the model checker CpaChecker. We evaluated our tool on a collection of programs and a category of SvComp benchmarks. In our experiments, we observed an improvement in branch coverage compared to Crest from 48% to 63% in the best case, and from 66% to 71% on average.},
author = {Daca, Przemyslaw and Gupta, Ashutosh and Henzinger, Thomas A},
location = {St. Petersburg, FL, USA},
pages = {328 -- 347},
publisher = {Springer},
title = {{Abstraction-driven concolic testing}},
doi = {10.1007/978-3-662-49122-5_16},
volume = {9583},
year = {2016},
}
@inproceedings{1526,
abstract = {We present the first study of robustness of systems that are both timed as well as reactive (I/O). We study the behavior of such timed I/O systems in the presence of uncertain inputs and formalize their robustness using the analytic notion of Lipschitz continuity: a timed I/O system is K-(Lipschitz) robust if the perturbation in its output is at most K times the perturbation in its input. We quantify input and output perturbation using similarity functions over timed words such as the timed version of the Manhattan distance and the Skorokhod distance. We consider two models of timed I/O systems — timed transducers and asynchronous sequential circuits. We show that K-robustness of timed transducers can be decided in polynomial space under certain conditions. For asynchronous sequential circuits, we reduce K-robustness w.r.t. timed Manhattan distances to K-robustness of discrete letter-to-letter transducers and show PSpace-completeness of the problem.},
author = {Henzinger, Thomas A and Otop, Jan and Samanta, Roopsha},
location = {St. Petersburg, FL, USA},
pages = {250 -- 267},
publisher = {Springer},
title = {{Lipschitz robustness of timed I/O systems}},
doi = {10.1007/978-3-662-49122-5_12},
volume = {9583},
year = {2016},
}
@inproceedings{1541,
abstract = {We present XSpeed a parallel state-space exploration algorithm for continuous systems with linear dynamics and nondeterministic inputs. The motivation of having parallel algorithms is to exploit the computational power of multi-core processors to speed-up performance. The parallelization is achieved on two fronts. First, we propose a parallel implementation of the support function algorithm by sampling functions in parallel. Second, we propose a parallel state-space exploration by slicing the time horizon and computing the reachable states in the time slices in parallel. The second method can be however applied only to a class of linear systems with invertible dynamics and fixed input. A GP-GPU implementation is also presented following a lazy evaluation strategy on support functions. The parallel algorithms are implemented in the tool XSpeed. We evaluated the performance on two benchmarks including an 28 dimension Helicopter model. Comparison with the sequential counterpart shows a maximum speed-up of almost 7× on a 6 core, 12 thread Intel Xeon CPU E5-2420 processor. Our GP-GPU implementation shows a maximum speed-up of 12× over the sequential implementation and 53× over SpaceEx (LGG scenario), the state of the art tool for reachability analysis of linear hybrid systems. Experiments illustrate that our parallel algorithm with time slicing not only speeds-up performance but also improves precision.},
author = {Ray, Rajarshi and Gurung, Amit and Das, Binayak and Bartocci, Ezio and Bogomolov, Sergiy and Grosu, Radu},
location = {Haifa, Israel},
pages = {3 -- 18},
publisher = {Springer},
title = {{XSpeed: Accelerating reachability analysis on multi-core processors}},
doi = {10.1007/978-3-319-26287-1_1},
volume = {9434},
year = {2015},
}
@article{1539,
abstract = {Many stochastic models of biochemical reaction networks contain some chemical species for which the number of molecules that are present in the system can only be finite (for instance due to conservation laws), but also other species that can be present in arbitrarily large amounts. The prime example of such networks are models of gene expression, which typically contain a small and finite number of possible states for the promoter but an infinite number of possible states for the amount of mRNA and protein. One of the main approaches to analyze such models is through the use of equations for the time evolution of moments of the chemical species. Recently, a new approach based on conditional moments of the species with infinite state space given all the different possible states of the finite species has been proposed. It was argued that this approach allows one to capture more details about the full underlying probability distribution with a smaller number of equations. Here, I show that the result that less moments provide more information can only stem from an unnecessarily complicated description of the system in the classical formulation. The foundation of this argument will be the derivation of moment equations that describe the complete probability distribution over the finite state space but only low-order moments over the infinite state space. I will show that the number of equations that is needed is always less than what was previously claimed and always less than the number of conditional moment equations up to the same order. To support these arguments, a symbolic algorithm is provided that can be used to derive minimal systems of unconditional moment equations for models with partially finite state space. },
author = {Ruess, Jakob},
journal = {Journal of Chemical Physics},
number = {24},
publisher = {American Institute of Physics},
title = {{Minimal moment equations for stochastic models of biochemical reaction networks with partially finite state space}},
doi = {10.1063/1.4937937},
volume = {143},
year = {2015},
}
@inproceedings{1692,
abstract = {Computing an approximation of the reachable states of a hybrid system is a challenge, mainly because overapproximating the solutions of ODEs with a finite number of sets does not scale well. Using template polyhedra can greatly reduce the computational complexity, since it replaces complex operations on sets with a small number of optimization problems. However, the use of templates may make the over-approximation too conservative. Spurious transitions, which are falsely considered reachable, are particularly detrimental to performance and accuracy, and may exacerbate the state explosion problem. In this paper, we examine how spurious transitions can be avoided with minimal computational effort. To this end, detecting spurious transitions is reduced to the well-known problem of showing that two convex sets are disjoint by finding a hyperplane that separates them. We generalize this to owpipes by considering hyperplanes that evolve with time in correspondence to the dynamics of the system. The approach is implemented in the model checker SpaceEx and demonstrated on examples.},
author = {Frehse, Goran and Bogomolov, Sergiy and Greitschus, Marius and Strump, Thomas and Podelski, Andreas},
booktitle = {Proceedings of the 18th International Conference on Hybrid Systems: Computation and Control},
isbn = {978-1-4503-3433-4},
location = {Seattle, WA, United States},
pages = {149 -- 158},
publisher = {ACM},
title = {{Eliminating spurious transitions in reachability with support functions}},
doi = {10.1145/2728606.2728622},
year = {2015},
}
@article{1680,
abstract = {We consider the satisfiability problem for modal logic over first-order definable classes of frames.We confirm the conjecture from Hemaspaandra and Schnoor [2008] that modal logic is decidable over classes definable by universal Horn formulae. We provide a full classification of Horn formulae with respect to the complexity of the corresponding satisfiability problem. It turns out, that except for the trivial case of inconsistent formulae, local satisfiability is eitherNP-complete or PSPACE-complete, and global satisfiability is NP-complete, PSPACE-complete, or ExpTime-complete. We also show that the finite satisfiability problem for modal logic over Horn definable classes of frames is decidable. On the negative side, we show undecidability of two related problems. First, we exhibit a simple universal three-variable formula defining the class of frames over which modal logic is undecidable. Second, we consider the satisfiability problem of bimodal logic over Horn definable classes of frames, and also present a formula leading to undecidability.},
author = {Michaliszyn, Jakub and Otop, Jan and Kieroňski, Emanuel},
journal = {ACM Transactions on Computational Logic},
number = {1},
publisher = {ACM},
title = {{On the decidability of elementary modal logics}},
doi = {10.1145/2817825},
volume = {17},
year = {2015},
}
@inproceedings{1659,
abstract = {The target discounted-sum problem is the following: Given a rational discount factor 0 < λ < 1 and three rational values a, b, and t, does there exist a finite or an infinite sequence w ε(a, b)∗ or w ε(a, b)w, such that Σ|w| i=0 w(i)λi equals t? The problem turns out to relate to many fields of mathematics and computer science, and its decidability question is surprisingly hard to solve. We solve the finite version of the problem, and show the hardness of the infinite version, linking it to various areas and open problems in mathematics and computer science: β-expansions, discounted-sum automata, piecewise affine maps, and generalizations of the Cantor set. We provide some partial results to the infinite version, among which are solutions to its restriction to eventually-periodic sequences and to the cases that λ λ 1/2 or λ = 1/n, for every n ε N. We use our results for solving some open problems on discounted-sum automata, among which are the exact-value problem for nondeterministic automata over finite words and the universality and inclusion problems for functional automata.},
author = {Boker, Udi and Henzinger, Thomas A and Otop, Jan},
booktitle = {LICS},
issn = {1043-6871 },
location = {Kyoto, Japan},
pages = {750 -- 761},
publisher = {IEEE},
title = {{The target discounted-sum problem}},
doi = {10.1109/LICS.2015.74},
year = {2015},
}
@article{1856,
abstract = {The traditional synthesis question given a specification asks for the automatic construction of a system that satisfies the specification, whereas often there exists a preference order among the different systems that satisfy the given specification. Under a probabilistic assumption about the possible inputs, such a preference order is naturally expressed by a weighted automaton, which assigns to each word a value, such that a system is preferred if it generates a higher expected value. We solve the following optimal synthesis problem: given an omega-regular specification, a Markov chain that describes the distribution of inputs, and a weighted automaton that measures how well a system satisfies the given specification under the input assumption, synthesize a system that optimizes the measured value. For safety specifications and quantitative measures that are defined by mean-payoff automata, the optimal synthesis problem reduces to finding a strategy in a Markov decision process (MDP) that is optimal for a long-run average reward objective, which can be achieved in polynomial time. For general omega-regular specifications along with mean-payoff automata, the solution rests on a new, polynomial-time algorithm for computing optimal strategies in MDPs with mean-payoff parity objectives. Our algorithm constructs optimal strategies that consist of two memoryless strategies and a counter. The counter is in general not bounded. To obtain a finite-state system, we show how to construct an ε-optimal strategy with a bounded counter, for all ε > 0. Furthermore, we show how to decide in polynomial time if it is possible to construct an optimal finite-state system (i.e., a system without a counter) for a given specification. We have implemented our approach and the underlying algorithms in a tool that takes qualitative and quantitative specifications and automatically constructs a system that satisfies the qualitative specification and optimizes the quantitative specification, if such a system exists. We present some experimental results showing optimal systems that were automatically generated in this way.},
author = {Chatterjee, Krishnendu and Henzinger, Thomas A and Jobstmann, Barbara and Singh, Rohit},
journal = {Journal of the ACM},
number = {1},
publisher = {ACM},
title = {{Measuring and synthesizing systems in probabilistic environments}},
doi = {10.1145/2699430},
volume = {62},
year = {2015},
}
@inproceedings{1882,
abstract = {We provide a framework for compositional and iterative design and verification of systems with quantitative information, such as rewards, time or energy. It is based on disjunctive modal transition systems where we allow actions to bear various types of quantitative information. Throughout the design process the actions can be further refined and the information made more precise. We show how to compute the results of standard operations on the systems, including the quotient (residual), which has not been previously considered for quantitative non-deterministic systems. Our quantitative framework has close connections to the modal nu-calculus and is compositional with respect to general notions of distances between systems and the standard operations.},
author = {Fahrenberg, Uli and Kretinsky, Jan and Legay, Axel and Traonouez, Louis},
location = {Bertinoro, Italy},
pages = {306 -- 324},
publisher = {Springer},
title = {{Compositionality for quantitative specifications}},
doi = {10.1007/978-3-319-15317-9_19},
volume = {8997},
year = {2015},
}
@article{1832,
abstract = {Linearizability of concurrent data structures is usually proved by monolithic simulation arguments relying on the identification of the so-called linearization points. Regrettably, such proofs, whether manual or automatic, are often complicated and scale poorly to advanced non-blocking concurrency patterns, such as helping and optimistic updates. In response, we propose a more modular way of checking linearizability of concurrent queue algorithms that does not involve identifying linearization points. We reduce the task of proving linearizability with respect to the queue specification to establishing four basic properties, each of which can be proved independently by simpler arguments. As a demonstration of our approach, we verify the Herlihy and Wing queue, an algorithm that is challenging to verify by a simulation proof. },
author = {Chakraborty, Soham and Henzinger, Thomas A and Sezgin, Ali and Vafeiadis, Viktor},
journal = {Logical Methods in Computer Science},
number = {1},
publisher = {International Federation of Computational Logic},
title = {{Aspect-oriented linearizability proofs}},
doi = {10.2168/LMCS-11(1:20)2015},
volume = {11},
year = {2015},
}
@inproceedings{1729,
abstract = {We present a computer-aided programming approach to concurrency. The approach allows programmers to program assuming a friendly, non-preemptive scheduler, and our synthesis procedure inserts synchronization to ensure that the final program works even with a preemptive scheduler. The correctness specification is implicit, inferred from the non-preemptive behavior. Let us consider sequences of calls that the program makes to an external interface. The specification requires that any such sequence produced under a preemptive scheduler should be included in the set of such sequences produced under a non-preemptive scheduler. The solution is based on a finitary abstraction, an algorithm for bounded language inclusion modulo an independence relation, and rules for inserting synchronization. We apply the approach to device-driver programming, where the driver threads call the software interface of the device and the API provided by the operating system. Our experiments demonstrate that our synthesis method is precise and efficient, and, since it does not require explicit specifications, is more practical than the conventional approach based on user-provided assertions.},
author = {Cerny, Pavol and Clarke, Edmund and Henzinger, Thomas A and Radhakrishna, Arjun and Ryzhyk, Leonid and Samanta, Roopsha and Tarrach, Thorsten},
location = {San Francisco, CA, United States},
pages = {180 -- 197},
publisher = {Springer},
title = {{From non-preemptive to preemptive scheduling using synchronization synthesis}},
doi = {10.1007/978-3-319-21668-3_11},
volume = {9207},
year = {2015},
}
@article{1731,
abstract = {We consider two-player zero-sum games on graphs. These games can be classified on the basis of the information of the players and on the mode of interaction between them. On the basis of information the classification is as follows: (a) partial-observation (both players have partial view of the game); (b) one-sided complete-observation (one player has complete observation); and (c) complete-observation (both players have complete view of the game). On the basis of mode of interaction we have the following classification: (a) concurrent (both players interact simultaneously); and (b) turn-based (both players interact in turn). The two sources of randomness in these games are randomness in transition function and randomness in strategies. In general, randomized strategies are more powerful than deterministic strategies, and randomness in transitions gives more general classes of games. In this work we present a complete characterization for the classes of games where randomness is not helpful in: (a) the transition function probabilistic transition can be simulated by deterministic transition); and (b) strategies (pure strategies are as powerful as randomized strategies). As consequence of our characterization we obtain new undecidability results for these games. },
author = {Chatterjee, Krishnendu and Doyen, Laurent and Gimbert, Hugo and Henzinger, Thomas A},
journal = {Information and Computation},
number = {12},
pages = {3 -- 16},
publisher = {Elsevier},
title = {{Randomness for free}},
doi = {10.1016/j.ic.2015.06.003},
volume = {245},
year = {2015},
}
@article{1840,
abstract = {In this paper, we present a method for reducing a regular, discrete-time Markov chain (DTMC) to another DTMC with a given, typically much smaller number of states. The cost of reduction is defined as the Kullback-Leibler divergence rate between a projection of the original process through a partition function and a DTMC on the correspondingly partitioned state space. Finding the reduced model with minimal cost is computationally expensive, as it requires an exhaustive search among all state space partitions, and an exact evaluation of the reduction cost for each candidate partition. Our approach deals with the latter problem by minimizing an upper bound on the reduction cost instead of minimizing the exact cost. The proposed upper bound is easy to compute and it is tight if the original chain is lumpable with respect to the partition. Then, we express the problem in the form of information bottleneck optimization, and propose using the agglomerative information bottleneck algorithm for searching a suboptimal partition greedily, rather than exhaustively. The theory is illustrated with examples and one application scenario in the context of modeling bio-molecular interactions.},
author = {Geiger, Bernhard and Petrov, Tatjana and Kubin, Gernot and Koeppl, Heinz},
issn = {0018-9286},
journal = {IEEE Transactions on Automatic Control},
number = {4},
pages = {1010 -- 1022},
publisher = {IEEE},
title = {{Optimal Kullback-Leibler aggregation via information bottleneck}},
doi = {10.1109/TAC.2014.2364971},
volume = {60},
year = {2015},
}
@inproceedings{1605,
abstract = {Multiaffine hybrid automata (MHA) represent a powerful formalism to model complex dynamical systems. This formalism is particularly suited for the representation of biological systems which often exhibit highly non-linear behavior. In this paper, we consider the problem of parameter identification for MHA. We present an abstraction of MHA based on linear hybrid automata, which can be analyzed by the SpaceEx model checker. This abstraction enables a precise handling of time-dependent properties. We demonstrate the potential of our approach on a model of a genetic regulatory network and a myocyte model.},
author = {Bogomolov, Sergiy and Schilling, Christian and Bartocci, Ezio and Batt, Grégory and Kong, Hui and Grosu, Radu},
location = {Haifa, Israel},
pages = {19 -- 35},
publisher = {Springer},
title = {{Abstraction-based parameter synthesis for multiaffine systems}},
doi = {10.1007/978-3-319-26287-1_2},
volume = {9434},
year = {2015},
}