401 research outputs found
Software Model Checking by Program Specialization
We introduce a general verification framework based on program specialization to prove properties of the runtime behaviour of imperative programs. Given a program P written in a programming language L and a property phi in a logic M, we can verify that phi holds for P by: (i) writing an interpreter I for L and a semantics S
for M in a suitable metalanguage, (ii) specializing I and S with respect to P and phi, and (iii) analysing the specialized program by performing a further specialization. We have instantiated our framework to verify safety properties of a simple imperative language, called SIMP, extended with a nondeterministic choice operator. The method is fully automatic and it has been implemented using the MAP transformation system
Verification of Imperative Programs by Constraint Logic Program Transformation
We present a method for verifying partial correctness properties of
imperative programs that manipulate integers and arrays by using techniques
based on the transformation of constraint logic programs (CLP). We use CLP as a
metalanguage for representing imperative programs, their executions, and their
properties. First, we encode the correctness of an imperative program, say
prog, as the negation of a predicate 'incorrect' defined by a CLP program T. By
construction, 'incorrect' holds in the least model of T if and only if the
execution of prog from an initial configuration eventually halts in an error
configuration. Then, we apply to program T a sequence of transformations that
preserve its least model semantics. These transformations are based on
well-known transformation rules, such as unfolding and folding, guided by
suitable transformation strategies, such as specialization and generalization.
The objective of the transformations is to derive a new CLP program TransfT
where the predicate 'incorrect' is defined either by (i) the fact 'incorrect.'
(and in this case prog is not correct), or by (ii) the empty set of clauses
(and in this case prog is correct). In the case where we derive a CLP program
such that neither (i) nor (ii) holds, we iterate the transformation. Since the
problem is undecidable, this process may not terminate. We show through
examples that our method can be applied in a rather systematic way, and is
amenable to automation by transferring to the field of program verification
many techniques developed in the field of program transformation.Comment: In Proceedings Festschrift for Dave Schmidt, arXiv:1309.455
Enhancing Predicate Pairing with Abstraction for Relational Verification
Relational verification is a technique that aims at proving properties that
relate two different program fragments, or two different program runs. It has
been shown that constrained Horn clauses (CHCs) can effectively be used for
relational verification by applying a CHC transformation, called predicate
pairing, which allows the CHC solver to infer relations among arguments of
different predicates. In this paper we study how the effects of the predicate
pairing transformation can be enhanced by using various abstract domains based
on linear arithmetic (i.e., the domain of convex polyhedra and some of its
subdomains) during the transformation. After presenting an algorithm for
predicate pairing with abstraction, we report on the experiments we have
performed on over a hundred relational verification problems by using various
abstract domains. The experiments have been performed by using the VeriMAP
transformation and verification system, together with the Parma Polyhedra
Library (PPL) and the Z3 solver for CHCs.Comment: Pre-proceedings paper presented at the 27th International Symposium
on Logic-Based Program Synthesis and Transformation (LOPSTR 2017), Namur,
Belgium, 10-12 October 2017 (arXiv:1708.07854
Proving Correctness of Imperative Programs by Linearizing Constrained Horn Clauses
We present a method for verifying the correctness of imperative programs
which is based on the automated transformation of their specifications. Given a
program prog, we consider a partial correctness specification of the form
prog , where the assertions and are
predicates defined by a set Spec of possibly recursive Horn clauses with linear
arithmetic (LA) constraints in their premise (also called constrained Horn
clauses). The verification method consists in constructing a set PC of
constrained Horn clauses whose satisfiability implies that prog
is valid. We highlight some limitations of state-of-the-art
constrained Horn clause solving methods, here called LA-solving methods, which
prove the satisfiability of the clauses by looking for linear arithmetic
interpretations of the predicates. In particular, we prove that there exist
some specifications that cannot be proved valid by any of those LA-solving
methods. These specifications require the proof of satisfiability of a set PC
of constrained Horn clauses that contain nonlinear clauses (that is, clauses
with more than one atom in their premise). Then, we present a transformation,
called linearization, that converts PC into a set of linear clauses (that is,
clauses with at most one atom in their premise). We show that several
specifications that could not be proved valid by LA-solving methods, can be
proved valid after linearization. We also present a strategy for performing
linearization in an automatic way and we report on some experimental results
obtained by using a preliminary implementation of our method.Comment: To appear in Theory and Practice of Logic Programming (TPLP),
Proceedings of ICLP 201
Issue Yield and Party Strategy in Multiparty Competition
The issue yield model introduced a theory of the herestethic use of policy issues as strategic resources in multidimensional party competition. We extend the model by systematically addressing the specificities of issue yield dynamics in multiparty systems, with special regard to parties\u2019 issue yield rankings (relative position) and issue yield heterogeneity (differentiation) on each issue. Second, we introduce a novel research design for original data collection that allows for a more systematic testing of the model, by featuring (a) a large number of policy issues, (b) the use of Twitter content for coding parties\u2019 issue emphasis, and (c) an appropriate time sequence for measuring issue yield configurations and issue emphasis. We finally present findings from a pilot implementation of such design, performed on the occasion of the 2014 European Parliament election in Italy. Findings confirm the soundness of the design and provide support for the newly introduced hypotheses about multiparty competition
CHC-COMP 2022: Competition Report
CHC-COMP 2022 is the fifth edition of the competition of solvers for
Constrained Horn Clauses. The competition was run in March 2022; the results
were presented at the 9th Workshop on Horn Clauses for Verification and
Synthesis held in Munich, Germany, on April 3, 2022. This edition featured six
solvers, and eight tracks consisting of sets of linear and nonlinear clauses
with constraints over linear integer arithmetic, linear real arithmetic,
arrays, and algebraic data types. This report provides an overview of the
organization behind the competition runs: it includes the technical details of
the competition setup as well as presenting the results of the 2022 edition.Comment: In Proceedings HCVS/VPT 2022, arXiv:2211.10675. arXiv admin note:
text overlap with arXiv:2109.04635, arXiv:2008.02939 by other author
Considerations on dynamic soaring
This paper presents an analytical treatment of dynamic soaring, a behaviour that certain sea birds use to extract energy from wind gradient. Theoretical modeling and results of numerical simulations, based on a two-degrees-of-freedom point mass model, are presented
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