2,118 research outputs found
The JKind Model Checker
JKind is an open-source industrial model checker developed by Rockwell
Collins and the University of Minnesota. JKind uses multiple parallel engines
to prove or falsify safety properties of infinite state models. It is portable,
easy to install, performance competitive with other state-of-the-art model
checkers, and has features designed to improve the results presented to users:
inductive validity cores for proofs and counterexample smoothing for test-case
generation. It serves as the back-end for various industrial applications.Comment: CAV 201
Abstraction in directed model checking
Abstraction is one of the most important issues to cope with large and infinite state spaces in model checking and to reduce the verification efforts. The abstract system is smaller than the original one and if the abstract system satisfies a correctness specification, so does the concrete one. However, abstractions may introduce a behavior violating the specification that is not present in the original system.
This paper bypasses this problem by proposing the combination of abstraction with heuristic search to improve error detection. The abstract system is explored in order to create a database that stores the exact distances from abstract states to the set of abstract error states. To check, whether or not the abstract behavior is present in the original system, effcient exploration algorithms exploit the database as a guidance
Simplifying Contract-Violating Traces
Contract conformance is hard to determine statically, prior to the deployment
of large pieces of software. A scalable alternative is to monitor for contract
violations post-deployment: once a violation is detected, the trace
characterising the offending execution is analysed to pinpoint the source of
the offence. A major drawback with this technique is that, often, contract
violations take time to surface, resulting in long traces that are hard to
analyse. This paper proposes a methodology together with an accompanying tool
for simplifying traces and assisting contract-violation debugging.Comment: In Proceedings FLACOS 2012, arXiv:1209.169
Fault Localization in Multi-Threaded C Programs using Bounded Model Checking (extended version)
Software debugging is a very time-consuming process, which is even worse for
multi-threaded programs, due to the non-deterministic behavior of
thread-scheduling algorithms. However, the debugging time may be greatly
reduced, if automatic methods are used for localizing faults. In this study, a
new method for fault localization, in multi-threaded C programs, is proposed.
It transforms a multi-threaded program into a corresponding sequential one and
then uses a fault-diagnosis method suitable for this type of program, in order
to localize faults. The code transformation is implemented with rules and
context switch information from counterexamples, which are typically generated
by bounded model checkers. Experimental results show that the proposed method
is effective, in such a way that sequential fault-localization methods can be
extended to multi-threaded programs.Comment: extended version of paper published at SBESC'1
Counterexample Generation in Probabilistic Model Checking
Providing evidence for the refutation of a property is an essential, if not the most important, feature of model checking. This paper considers algorithms for counterexample generation for probabilistic CTL formulae in discrete-time Markov chains. Finding the strongest evidence (i.e., the most probable path) violating a (bounded) until-formula is shown to be reducible to a single-source (hop-constrained) shortest path problem. Counterexamples of smallest size that deviate most from the required probability bound can be obtained by applying (small amendments to) k-shortest (hop-constrained) paths algorithms. These results can be extended to Markov chains with rewards, to LTL model checking, and are useful for Markov decision processes. Experimental results show that typically the size of a counterexample is excessive. To obtain much more compact representations, we present a simple algorithm to generate (minimal) regular expressions that can act as counterexamples. The feasibility of our approach is illustrated by means of two communication protocols: leader election in an anonymous ring network and the Crowds protocol
Quantum ground state isoperimetric inequalities for the energy spectrum of local Hamiltonians
We investigate the relationship between the energy spectrum of a local
Hamiltonian and the geometric properties of its ground state. By generalizing a
standard framework from the analysis of Markov chains to arbitrary
(non-stoquastic) Hamiltonians we are naturally led to see that the spectral gap
can always be upper bounded by an isoperimetric ratio that depends only on the
ground state probability distribution and the range of the terms in the
Hamiltonian, but not on any other details of the interaction couplings. This
means that for a given probability distribution the inequality constrains the
spectral gap of any local Hamiltonian with this distribution as its ground
state probability distribution in some basis (Eldar and Harrow derived a
similar result in order to characterize the output of low-depth quantum
circuits). Going further, we relate the Hilbert space localization properties
of the ground state to higher energy eigenvalues by showing that the presence
of k strongly localized ground state modes (i.e. clusters of probability, or
subsets with small expansion) in Hilbert space implies the presence of k energy
eigenvalues that are close to the ground state energy. Our results suggest that
quantum adiabatic optimization using local Hamiltonians will inevitably
encounter small spectral gaps when attempting to prepare ground states
corresponding to multi-modal probability distributions with strongly localized
modes, and this problem cannot necessarily be alleviated with the inclusion of
non-stoquastic couplings
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