Sriram Sankaranarayanan

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S-TaLiRo is a Matlab (TM) toolbox that searches for tra-jectories of minimal robustness in Simulink/Stateflow diagrams. It can analyze arbitrary Simulink models or user defined functions that model the system. At the heart of the tool, we use randomized testing based on stochastic optimization techniques including Monte-Carlo methods and Ant-Colony(More)
We present a new method for the generation of linear in-variants which reduces the problem to a non-linear constraint solving problem. Our method, based on Farkas' Lemma, synthesizes linear in-variants by extracting non-linear constraints on the coefficients of a target invariant from a program. These constraints guarantee that the linear invariant is(More)
We present a method for generating linear invariants for large systems. The method performs forward propagation in an abstract domain consisting of arbitrary polyhedra of a predefined fixed shape. The basic operations on the domain like abstraction, intersection, join and inclusion tests are all posed as linear optimization queries, which can be solved(More)
We present a new method for generating algebraic invariants of hybrid systems. The method reduces the invariant generation problem to a constraint solving problem using techniques from the theory of ideals over polynomial rings. Starting with a template invariant – a polynomial equality over the system variables with unknown coefficients – constraints are(More)
—We propose a novel integration of interval constraint propagation (ICP) with SMT solvers for linear real arithmetic (LRA) to decide nonlinear real arithmetic problems. We use ICP to search for interval solutions of the nonlinear constraints, and use the LRA solver to either validate the solutions or provide constraints to incrementally refine the search(More)
Lyapunov functions are used to prove stability and to obtain performance bounds on system behaviors for nonlinear and hybrid dynamical systems, but discovering Lyapunov functions is a difficult task in general. We present a technique for discovering Lyapunov functions and barrier certificates for nonlinear and hybrid dynamical systems using a search-based(More)
Methods in object-oriented concurrent libraries hide internal synchronization details. However, information hiding may result in clients causing thread safety violations by invoking methods in an unsafe manner.Given such a library, we present a technique for inferring interface contracts that specify permissible concurrent method calls and patterns of(More)
Linear-relations analysis of transition systems discovers linear invariant relationships among the variables of the system. These relationships help establish important safety and liveness properties. Efficient techniques for the analysis of systems using polyhedra have been explored, leading to the development of successful tools like HyTech. However,(More)
We present a Monte-Carlo optimization technique for finding inputs to a system that falsify a given Metric Temporal Logic (MTL) property. Our approach performs a random walk over the space of inputs guided by a robustness metric defined by the MTL property. Robustness can be used to guide our search for a falsifying trajectory by exploring trajectories with(More)
The convexity of numerical domains such as polyhedra, octagons , intervals and linear equalities enables tractable analysis of software for buffer overflows, null pointer dereferences and floating point errors. However, convexity also causes the analysis to fail in many common cases. Powerset extensions can remedy this shortcoming by considering(More)