45 research outputs found
Parameter Compilation
In resolving instances of a computational problem, if multiple instances of
interest share a feature in common, it may be fruitful to compile this feature
into a format that allows for more efficient resolution, even if the
compilation is relatively expensive. In this article, we introduce a formal
framework for classifying problems according to their compilability. The basic
object in our framework is that of a parameterized problem, which here is a
language along with a parameterization---a map which provides, for each
instance, a so-called parameter on which compilation may be performed. Our
framework is positioned within the paradigm of parameterized complexity, and
our notions are relatable to established concepts in the theory of
parameterized complexity. Indeed, we view our framework as playing a unifying
role, integrating together parameterized complexity and compilability theory
On the Complexity of Existential Positive Queries
We systematically investigate the complexity of model checking the
existential positive fragment of first-order logic. In particular, for a set of
existential positive sentences, we consider model checking where the sentence
is restricted to fall into the set; a natural question is then to classify
which sentence sets are tractable and which are intractable. With respect to
fixed-parameter tractability, we give a general theorem that reduces this
classification question to the corresponding question for primitive positive
logic, for a variety of representations of structures. This general theorem
allows us to deduce that an existential positive sentence set having bounded
arity is fixed-parameter tractable if and only if each sentence is equivalent
to one in bounded-variable logic. We then use the lens of classical complexity
to study these fixed-parameter tractable sentence sets. We show that such a set
can be NP-complete, and consider the length needed by a translation from
sentences in such a set to bounded-variable logic; we prove superpolynomial
lower bounds on this length using the theory of compilability, obtaining an
interesting type of formula size lower bound. Overall, the tools, concepts, and
results of this article set the stage for the future consideration of the
complexity of model checking on more expressive logics
Parameterized Compilation Lower Bounds for Restricted CNF-formulas
We show unconditional parameterized lower bounds in the area of knowledge
compilation, more specifically on the size of circuits in decomposable negation
normal form (DNNF) that encode CNF-formulas restricted by several graph width
measures. In particular, we show that
- there are CNF formulas of size and modular incidence treewidth
whose smallest DNNF-encoding has size , and
- there are CNF formulas of size and incidence neighborhood diversity
whose smallest DNNF-encoding has size .
These results complement recent upper bounds for compiling CNF into DNNF and
strengthen---quantitatively and qualitatively---known conditional low\-er
bounds for cliquewidth. Moreover, they show that, unlike for many graph
problems, the parameters considered here behave significantly differently from
treewidth
On the complexity of Existential Positive Queries
We systematically investigate the complexity of model checking the existential positive fragment of first-order logic. In particular, for a set of existential positive sentences, we consider model checking where the sentence is restricted to fall into the set; a natural question is then to classify which sentence sets are tractable and which are intractable. With respect to fixed-parameter tractability, we give a general theorem that reduces this classification question to the corresponding question for primitive positive logic, for a variety of representations of structures. This general theorem allows us to deduce that an existential positive sentence set having bounded arity is fixed-parameter tractable if and only if each sentence is equivalent to one in bounded-variable logic. We then use the lens of classical complexity to study these fixed-parameter tractable sentence sets. We show that such a set can be NP-complete, and consider the length needed by a translation from sentences in such a set to bounded-variable logic; we prove superpolynomial lower bounds on this length using the theory of compilability, obtaining an interesting type of formula size lower bound. Overall, the tools, concepts, and results of this article set the stage for the future consideration of the complexity of model checking on more expressive logics
Quantum utility -- definition and assessment of a practical quantum advantage
Several benchmarks have been proposed to holistically measure quantum
computing performance. While some have focused on the end user's perspective
(e.g., in application-oriented benchmarks), the real industrial value taking
into account the physical footprint of the quantum processor are not discussed.
Different use-cases come with different requirements for size, weight, power
consumption, or data privacy while demanding to surpass certain thresholds of
fidelity, speed, problem size, or precision. This paper aims to incorporate
these characteristics into a concept coined quantum utility, which demonstrates
the effectiveness and practicality of quantum computers for various
applications where quantum advantage -- defined as either being faster, more
accurate, or demanding less energy -- is achieved over a classical machine of
similar size, weight, and cost. To successively pursue quantum utility, a
level-based classification scheme -- constituted as application readiness
levels (ARLs) -- as well as extended classification labels are introduced.
These are demonstratively applied to different quantum applications from the
fields of quantum chemistry, quantum simulation, quantum machine learning, and
data analysis followed by a brief discussion
Automatic Refactoring for Renamed Clones in Test Code
Unit testing plays an essential role in software development and maintenance, especially in Test-Driven Development. Conventional unit tests, which have no input parameters, often exercise similar scenarios with small variations to achieve acceptable coverage, which often results in duplicated code in test suites. Test code duplication hinders comprehension of test cases and maintenance of test suites. Test refactoring is a potential tool for developers to use to control technical debt arising due to test cloning.
In this thesis, we present a novel tool, JTestParametrizer, for automatically refactoring method-scope renamed clones in test suites. We propose three levels of refactoring to parameterize type, data, and behaviour differences in clone pairs. Our technique works at the Abstract Syntax Tree level by extracting a parameterized template utility method and
instantiating it with appropriate parameter values.
We applied our technique to 5 open-source Java benchmark projects and conducted an empirical study on our results. Our technique examined 14,431 test methods in our benchmark projects and identified 415 renamed clone pairs as effective candidates for refactoring. On average, 65% of the effective candidates (268 clone pairs) in our test suites are refactorable using our technique. All of the refactored test methods are compilable, and 94% of them pass when executed as tests. We believe that our proposed refactorings generally improve code conciseness, reduce the amount of duplication, and make test suites easier to maintain and extend
Timed Transition Automata as Numerical Planning Domain
A general technique for transforming a timed finite state automaton into an equivalent automated
planning domain based on a numerical parameter model is introduced. Timed transition automata have many
applications in control systems and agents models; they are used to describe sequential processes, where
actions are labelling by automaton transitions subject to temporal constraints. The language of timed words
accepted by a timed automaton, the possible sequences of system or agent behaviour, can be described in term
of an appropriate planning domain encapsulating the timed actions patterns and constraints. The time words
recognition problem is then posed as a planning problem where the goal is to reach a final state by a sequence of
actions, which corresponds to the timed symbols labeling the automaton transitions. The transformation is proved
to be correct and complete and it is space/time linear on the automaton size. Experimental results shows that the
performance of the planning domain obtained by transformation is scalable for real world applications. A major
advantage of the planning based approach, beside of the solving the parsing problem, is to represent in a single
automated reasoning framework problems of plan recognitions, plan synthesis and plan optimisation