375 research outputs found
Efficient Generation of Craig Interpolants in Satisfiability Modulo Theories
The problem of computing Craig Interpolants has recently received a lot of
interest. In this paper, we address the problem of efficient generation of
interpolants for some important fragments of first order logic, which are
amenable for effective decision procedures, called Satisfiability Modulo Theory
solvers.
We make the following contributions.
First, we provide interpolation procedures for several basic theories of
interest: the theories of linear arithmetic over the rationals, difference
logic over rationals and integers, and UTVPI over rationals and integers.
Second, we define a novel approach to interpolate combinations of theories,
that applies to the Delayed Theory Combination approach.
Efficiency is ensured by the fact that the proposed interpolation algorithms
extend state of the art algorithms for Satisfiability Modulo Theories. Our
experimental evaluation shows that the MathSAT SMT solver can produce
interpolants with minor overhead in search, and much more efficiently than
other competitor solvers.Comment: submitted to ACM Transactions on Computational Logic (TOCL
Efficient Interpolant Generation in Satisfiability Modulo Theories
The problem of computing Craig Interpolants for propositional (SAT) formulas has recently received a lot of interest, mainly for its applications in formal verification. However, propositional logic is often not expressive enough for representing many interesting verification problems, which can be more naturally addressed in the framework of Satisfiability Modulo Theories, SMT. Although {some} works have addressed the topic of generating interpolants in SMT, the techniques and tools that are currently available have some limitations, and their performance still does not exploit the full power of current state-of-the-art SMT solvers. In this paper we try to close this gap. We present several techniques for interpolant generation in SMT which overcome the limitations of the current generators mentioned above, and which take full advantage of state-of-the-art SMT technology. These novel techniques can lead to substantial performance improvements wrt. the currently available tools. We support our claims with an extensive experimental evaluation of our implementation of the proposed techniques in the MathSAT SMT solver
A Simple and Flexible Way of Computing Small Unsatisfiable Cores in SAT Modulo Theories
Finding small unsatisfiable cores for SAT problems has recently received a lot of interest, mostly for its applications in formal verification. However, propositional logic is often not expressive enough for representing many interesting verification problems, which can be more naturally addressed in the framework of Satisfiability Modulo Theories, SMT. Surprisingly, the problem of finding unsatisfiable cores in SMT has received very little attention in the literature; in particular, we are not aware of any work aiming at producing small unsatisfiable cores in SMT. In this paper we present a novel approach to this problem. The main idea is to combine an SMT solver with an external propositional core extractor: the SMT solver produces the theory lemmas found during the search; the core extractor is then called on the boolean abstraction of the original SMT problem and of the theory lemmas. This results in an unsatisfiable core for the original SMT problem, once the remaining theory lemmas have been removed. The approach is conceptually interesting, since the SMT solver is used to dynamically lift the suitable amount of theory information to the boolean level, and it also has several advantages in practice. In fact, it is extremely simple to implement and to update, and it can be interfaced with every propositional core extractor in a plug-and-play manner, so that to benefit for free of all unsat-core reduction techniques which have been or will be made available. We have evaluated our approach by an extensive empirical test on SMT-LIB benchmarks, which confirms the validity and potential of this approach
Software Model Checking via Large-Block Encoding
The construction and analysis of an abstract reachability tree (ART) are the
basis for a successful method for software verification. The ART represents
unwindings of the control-flow graph of the program. Traditionally, a
transition of the ART represents a single block of the program, and therefore,
we call this approach single-block encoding (SBE). SBE may result in a huge
number of program paths to be explored, which constitutes a fundamental source
of inefficiency. We propose a generalization of the approach, in which
transitions of the ART represent larger portions of the program; we call this
approach large-block encoding (LBE). LBE may reduce the number of paths to be
explored up to exponentially. Within this framework, we also investigate
symbolic representations: for representing abstract states, in addition to
conjunctions as used in SBE, we investigate the use of arbitrary Boolean
formulas; for computing abstract-successor states, in addition to Cartesian
predicate abstraction as used in SBE, we investigate the use of Boolean
predicate abstraction. The new encoding leverages the efficiency of
state-of-the-art SMT solvers, which can symbolically compute abstract
large-block successors. Our experiments on benchmark C programs show that the
large-block encoding outperforms the single-block encoding.Comment: 13 pages (11 without cover), 4 figures, 5 table
Il fumetto secondo Calvino. Un tradimento tra linguaggio sequenziale e combinazione.
The aim of this essay is to outline how Calvino considers and âusesâ comics, as a language, as a narrative structure and as a commodity and cultural product, within his public and private writings and in the statements made in interviews. The research reviews the passages in which Calvino talks about comics or uses their specialist vocabulary, to define the author's readings and his comics imagery of reference, to outline the contexts of use and functions of these references and to understand which Calvino's idea ofââ âcomicsâ. The field of investigation, therefore, is the analysis of the discourse that the writer carries out on comics within his written production, with particular attention to the story Lâorigine degli uccelli and the project Il motel dei destini incrociati
Punk is dad. Parole e retorica negli articoli di Valerio Evangelisti
Analisi di stilemi di Valerio Evangelisti nella sua scrittura saggistica e pubblicistica, in particolare della sua produzione per la rivista musicale "Rolling Stone", consistente in una rubrica tenuta dal 2005 al 2007 sulla musica heavy metal, per la prima volta recensita e studiata in prospettiva linguistica e stilistica e in relazione alla poetica dell'autore
Viaggi nella polifonia: la scrittura di Gipi
Lo studio presenta un'analisi linguistica e stilistica della produzione a fumetti di Gipi, anche come sceneggiatore, individuando dove la lingua eÌ ubicata nelle sue tavole, rilevando l'importanza della scrittura da un punto di vista grafica, delineando come ottiene quella particolare polifonia che eÌ la sua cifra stilistica, tra letterarietaÌ, registri informali, dialetto, creativitaÌ lessicale. In particolare in Aldobrando (2020), disegnato da Luigi Critone, Gipi mostra di saper dare vita anche a un italiano "anticato", alla Armata Brancaleone di Monicelli, dall'effetto comico
La penna e lo spartito. Scrittori, musica e scrittura
Introduzione al volume monografico omonimo della rivista "Tratti" (n. 70, ottobre 2005), in cui sono pubblicate interviste di Alberto Sebastiani a 7 scrittori contemporanei (Aldo Gianolio, Paolo Nori, Enrico Brizzi, Gianluca Morozzi, Grazia Verasani, Guido Leotta, Emidio Clementi) sul loro lavoro in relazione alla musica, intesa come oggetto di scrittura, come realtaÌ e panorama culturale del mondo descritto nei loro testi, come complice nella creazione di un ritmo nella scrittur
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