Krishnendu Chatterjee

  1. Faster Algorithms for Alternating Refinement Relations.

    Authors: Krishnendu Chatterjee, Siddhesh Chaubal, Pritish Kamath
    Subjects: Logic in Computer Science
    Abstract

    One central issue in the formal design and analysis of reactive systems is
    the notion of refinement that asks whether all behaviors of the implementation
    is allowed by the specification. The local interpretation of behavior leads to
    the notion of simulation. Alternating transition systems (ATSs) provide a
    general model for composite reactive systems, and the simulation relation for
    ATSs is known as alternating simulation. The simulation relation for fair
    transition systems is called fair simulation.

  2. Bounded Rationality in Concurrent Parity Games.

    Authors: Krishnendu Chatterjee
    Subjects: Computer Science and Game Theory
    Abstract

    We consider 2-player games played on a finite state space for infinite
    rounds. The games are concurrent: in each round, the two players choose their
    moves simultaneously; the current state and the moves determine the successor.
    We consider omega-regular winning conditions given as parity objectives. We
    consider the qualitative analysis problems: the computation of the almost-sure
    and limit-sure winning set of states, where player 1 can ensure to win with
    probability 1 and with probability arbitrarily close to 1, respectively.

  3. Partial-Observation Stochastic Games: How to Win when Belief Fails.

    Authors: Krishnendu Chatterjee, Laurent Doyen
    Subjects: Computer Science and Game Theory
    Abstract

    In two-player finite-state stochastic games of partial observation on graphs,
    in every state of the graph, the players simultaneously choose an action, and
    their joint actions determine a probability distribution over the successor
    states. We consider reachability objectives where player 1 tries to ensure a
    target state to be visited almost-surely or positively. On the basis of
    information, the game can be one-sided with either (a)player 1 or (b)player 2
    having partial observation, or two-sided with both players having partial
    observation.

  4. Magnifying Lens Abstraction for Stochastic Games with Discounted and Long-run Average Objectives.

    Authors: Krishnendu Chatterjee, Luca de Alfaro, Pritam Roy
    Subjects: Computer Science and Game Theory
    Abstract

    Turn-based stochastic games and its important subclass Markov decision
    processes (MDPs) provide models for systems with both probabilistic and
    nondeterministic behaviors. We consider turn-based stochastic games with two
    classical quantitative objectives: discounted-sum and long-run average
    objectives. The game models and the quantitative objectives are widely used in
    probabilistic verification, planning, optimal inventory control, network
    protocol and performance analysis.

  5. Energy and Mean-Payoff Parity Markov Decision Processes.

    Authors: Krishnendu Chatterjee, Laurent Doyen
    Subjects: Computer Science and Game Theory
    Abstract

    We consider Markov Decision Processes (MDPs) with mean-payoff parity and
    energy parity objectives. In system design, the parity objective is used to
    encode \omega-regular specifications, and the mean-payoff and energy objectives
    can be used to model quantitative resource constraints. The energy condition
    requires that the resource level never drops below 0, and the mean-payoff
    condition requires that the limit-average value of the resource consumption is
    within a threshold.

  6. Expressiveness and Closure Properties for Quantitative Languages.

    Authors: Krishnendu Chatterjee, Laurent Doyen, Thomas A. Henzinger
    Subjects: Logic in Computer Science
    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. The value of a word $w$ is the
    supremum of the values of the runs over $w$. We study expressiveness and
    closure questions about these quantitative languages.

  7. Algorithms for Game Metrics.

    Authors: Krishnendu Chatterjee, Vishwanath Raman, Rupak Majumdar, Luca de Alfaro
    Subjects: Computer Science and Game Theory
    Abstract

    Simulation and bisimulation metrics for stochastic systems provide a
    quantitative generalization of the classical simulation and bisimulation
    relations. These metrics capture the similarity of states with respect to
    quantitative specifications written in the quantitative {\mu}-calculus and
    related probabilistic logics. We first show that the metrics provide a bound
    for the difference in long-run average and discounted average behavior across
    states, indicating that the metrics can be used both in system verification,
    and in performance evaluation.

  8. Assume-Guarantee Synthesis for Digital Contract Signing.

    Authors: Krishnendu Chatterjee, Vishwanath Raman
    Subjects: Logic in Computer Science
    Abstract

    We study the automatic synthesis of fair non-repudiation protocols, a class
    of fair exchange protocols, used for digital contract signing. First, we show
    how to specify the objectives of the participating agents and the trusted third
    party (TTP) as path formulas in LTL and prove that the satisfaction of these
    objectives imply fairness and abuse-freeness; properties required of fair
    exchange protocols. We then show that weak (co-operative) co-synthesis and
    classical (strictly competitive) co-synthesis fail, whereas assume-guarantee
    synthesis (AGS) succeeds.

  9. GIST: A Solver for Probabilistic Games.

    Authors: Krishnendu Chatterjee, Thomas A. Henzinger, Barbara Jobstmann, Arjun Radhakrishna
    Subjects: Logic in Computer Science
    Abstract

    Gist is a tool that (a) solves the qualitative analysis problem of turn-based
    probabilistic games with {\omega}-regular objectives; and (b) synthesizes
    reasonable environment assumptions for synthesis of unrealizable
    specifications. Our tool provides the first and efficient implementations of
    several reduction-based techniques to solve turn-based probabilistic games, and
    uses the analysis of turn-based probabilistic games for synthesizing
    environment assumptions for unrealizable specifications.

  10. Measuring and Synthesizing Systems in Probabilistic Environments.

    Authors: Krishnendu Chatterjee, Thomas A. Henzinger, Barbara Jobstmann, Rohit Singh
    Subjects: Logic in Computer Science
    Abstract

    Often one has a preference order among the different systems that satisfy a
    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.

  11. Energy Parity Games.

    Authors: Krishnendu Chatterjee, Laurent Doyen
    Subjects: Logic in Computer Science
    Abstract

    Energy parity games are infinite two-player turn-based games played on
    weighted graphs. The objective of the game combines a (qualitative) parity
    condition with the (quantitative) requirement that the sum of the weights
    (i.e., the level of energy in the game) must remain positive. Beside their own
    interest in the design and synthesis of resource-constrained omega-regular
    specifications, energy parity games provide one of the simplest model of games
    with combined qualitative and quantitative objective.

  12. Synthesis of AMBA AHB from Formal Specification.

    Authors: Krishnendu Chatterjee, Thomas A. Henzinger, Yashdeep Godhal
    Subjects: Logic in Computer Science
    Abstract

    The standard procedure for hardware design consists of describing circuit in
    a hardware description language at logic level followed by extensive
    verification and logic-synthesis. However, this process consumes significant
    time and needs a lot of effort. An alternative is to use formal specification
    language as a high-level hardware description language and synthesize hardware
    from formal specification. Bloem et.al. gave formal specifications and
    synthesize the AMBA AHB Arbiter.

  13. Probabilistic Weighted Automata.

    Authors: Krishnendu Chatterjee, Laurent Doyen, Thomas A. Henzinger
    Subjects: Logic in Computer Science
    Abstract

    Nondeterministic weighted automata are finite automata with numerical weights
    on transitions. They define quantitative languages L that assign to each word w
    a real number L(w). The value of an infinite word w is computed as the maximal
    value of all runs over w, and the value of a run as the maximum, limsup,
    liminf, limit average, or discounted sum of the transition weights. We
    introduce probabilistic weighted automata, in which the transitions are chosen
    in a randomized (rather than nondeterministic) fashion. Under almost-sure
    semantics (resp.

  14. Qualitative Analysis of Partially-observable Markov Decision Processes.

    Authors: Krishnendu Chatterjee, Laurent Doyen, Thomas A. Henzinger
    Subjects: Computer Science and Game Theory
    Abstract

    We study observation-based strategies for partially-observable Markov
    decision processes (POMDPs) with omega-regular objectives. An observation-based
    strategy relies on partial information about the history of a play, namely, on
    the past sequence of observations. We consider the qualitative analysis
    problem: given a POMDP with an omega-regular objective, whether there is an
    observation-based strategy to achieve the objective with probability~1
    (almost-sure winning), or with positive probability (positive winning). Our
    main results are twofold.

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