Showing papers by "Saurabh Srivastava published in 2009"

Program verification using templates over predicate abstraction

Abstract: We address the problem of automatically generating invariants with quantified and boolean structure for proving the validity of given assertions or generating pre-conditions under which the assertions are valid. We present three novel algorithms, having different strengths, that combine template and predicate abstraction based formalisms to discover required sophisticated program invariants using SMT solvers.Two of these algorithms use an iterative approach to compute fixed-points (one computes a least fixed-point and the other computes a greatest fixed-point), while the third algorithm uses a constraint based approach to encode the fixed-point. The key idea in all these algorithms is to reduce the problem of invariant discovery to that of finding optimal solutions for unknowns (over conjunctions of some predicates from a given set) in a template formula such that the formula is valid.Preliminary experiments using our implementation of these algorithms show encouraging results over a benchmark of small but complicated programs. Our algorithms can verify program properties that, to our knowledge, have not been automatically verified before. In particular, our algorithms can generate full correctness proofs for sorting algorithms (which requires nested universally-existentially quantified invariants) and can also generate preconditions required to establish worst-case upper bounds of sorting algorithms. Furthermore, for the case of previously considered properties, in particular sortedness in sorting algorithms, our algorithms take less time than reported by previous techniques.

VS3: SMT Solvers for Program Verification

Abstract: We present VS3, a tool that automatically verifies complex properties of programs and infers maximally weak preconditions and maximally strong postconditions by leveraging the power of SMT solvers. VS3 discovers program invariants with arbitrary, but prespecified, quantification and logical structure. The user supplies VS3 with a set of predicates and invariant templates. VS3 automatically finds instantiations of the unknowns in the templates as subsets of the predicate set. We have used VS3 to automatically verify *** *** properties of programs and to infer worst case upper bounds and preconditions for functional correctness.

Structural and magnetic phenomena in Ni53Mn25Al22 thin film prepared by rf magnetron sputtering

Abstract: Magnetic and structural properties of Ni–Mn–Al thin films are investigated. It is demonstrated that the annealed film shows L21 phase at room temperature. Magnetometry measurements reveal that the annealed film is ferromagnetic and a first order transition in magnetization versus temperature measurement confirms that the martensite to austenite transition occurs around room temperature. Transmission electron microscopy measurements confirm that this structural change occurs just below room temperature. The splitting of Mn 2p3/2 level in x-ray photoelectron spectroscopy core level spectra of the annealed Ni–Mn–Al film, confirms that the origin of magnetism is definitely correlated with the local magnetic moment at the Mn atoms.