18,900 research outputs found
A practical approach to the global analysis of CLP programs
This paper presents and illustrates with an example a practical approach to the dataflow analysis of programs written in constraint logic programming (CLP) languages using abstract interpretation. It is first argued that,
from the framework point of view, it sufnces to propose relatively simple extensions of traditional analysis methods which have already been proved useful and practical and for which efncient fixpoint algorithms have been
developed. This is shown by proposing a simple but quite general extensión of Bruynooghe's traditional framework to the analysis of CLP programs. In this extensión constraints are viewed not as "suspended goals" but rather as new information in the store, following the traditional view of CLP. Using this approach, and as an example of its use, a complete, constraint system independent, abstract analysis is presented for approximating definiteness information. The analysis is in fact of quite general applicability. It has been implemented and used in the analysis of CLP(R) and Prolog-III applications. Results from the implementation of this analysis are also presented
A practical application of sharing and freeness inference
Abstract is not available
Independence in constraint logic programs
Studying independence of literals, variables, and substitutions has proven very useful in the context of logic programming (LP). Here we study independence in the broader context of constraint logic programming (CLP). We show that a naive extrapolation of the LP definitions of independence to CLP is unsatisfactory (in fact, wrong) for two reasons. First, because interaction between variables through constraints is more complex than in the case of logic programming. Second, in order to ensure the efUciency of several optimizations not only must independence of the search space be considered, but also an orthogonal issue - "independence of constraint solving." We clarify these issues by proposing various types of search independence
and constraint solver independence, and show how they can be combined to allow different independence-related optimizations, from parallelism to intelligent backtracking. Sufficient conditions for independence which can be evaluated "a-priori" at run-time are also proposed. Our results suggest that independence, provided a suitable definition is chosen, is even more useful in CLP than in LP
Analyzing logic programs with dynamic scheduling
Traditional logic programming languages, such as Prolog, use a fixed left-to-right atom scheduling rule. Recent logic programming languages, however, usually provide more flexible scheduling in which computation generally proceeds leftto- right but in which some calis are dynamically
"delayed" until their arguments are sufRciently instantiated
to allow the cali to run efficiently. Such dynamic scheduling has a significant cost. We give a framework for the global analysis of logic programming languages with dynamic scheduling and show that program analysis based on this framework supports optimizations which remove much
of the overhead of dynamic scheduling
Homogeneous hydrodynamics of a collisional model of confined granular gases
The hydrodynamic equation governing the homogeneous time evolution of the
temperature in a model of confined granular gas is studied by means of the
Enskog equation. The existence of a normal solution of the kinetic equation is
assumed as a condition for hydrodynamics. Dimensional analysis implies a
scaling of the distribution function that is used to determine it in the first
Sonine approximation, with a coefficient that evolves in time through its
dependence on the temperature. The theoretical predictions are compared with
numerical results obtained by the direct simulation Monte Carlo method, and a
good agreement is found. The relevance of the normal homogeneous distribution
function to derive inhomogeneous hydrodynamic equations, for instance using the
Champan-Enskog algorithm, is indicated.Comment: Accepted in Phys. Rev.
Hydrodynamics for a model of a confined quasi-two-dimensional granular gas
The hydrodynamic equations for a model of a confined quasi-two-dimensional
gas of smooth inelastic hard spheres are derived from the Boltzmann equation
for the model, using a generalization of the Chapman-Enskog method. The heat
and momentum fluxes are calculated to Navier-Stokes order, and the associated
transport coefficients are explicitly determined as functions of the
coefficient of normal restitution and the velocity parameter involved in the
definition of the model. Also an Euler transport term contributing to the
energy transport equation is considered. This term arises from the gradient
expansion of the rate of change of the temperature due to the inelasticity of
collisions, and vanishes for elastic systems. The hydrodynamic equations are
particularized for the relevant case of a system in the homogeneous steady
state. The relationship with previous works is analyzed
Memory effects in the relaxation of a confined granular gas
The accuracy of a model to describe the horizontal dynamics of a confined
quasi-two-dimensional system of inelastic hard spheres is discussed by
comparing its predictions for the relaxation of the temperature in an
homogenous system with molecular dynamics simulation results for the original
system. A reasonably good agreement is found. Next, the model is used to
investigate the peculiarities of the nonlinear evolution of the temperature
when the parameter controlling the energy injection is instantaneously changed
while the system was relaxing. This can be considered as a non-equilibrium
generalization of the Kovacs effect. It is shown that, in the low density
limit, the effect can be accurately described by using a simple kinetic theory
based on the first Sonine approximation for the one-particle distribution
function. Some possible experimental implications are indicated
The CIAO multiparadigm compiler and system: A progress report
Abstract is not available
Expression of homoeologous molecular systems in wheat alloploids
Allopolyploidy is widespread in the plant kingdom, where it has been of considerable evolutionary significance. Although the existence of heterotic interactions between the genomes that make up an alloploid have been generally assumed, the precise nature of these interactions has not been extensively investigated. Presently available evidence about metabolic integration of the wheat genomes is examined in search of new insights about the different modes of genome interaction. Although additive expression seems to be the case for many homoeologous systems, more complex patterns of integration have become evident. Examples of enzyme subunit complementation, gene compensation and other dosage effects, holoprotein completion, and complementation of metabolic pathways are discussed
Locality and topology in the molecular Aharonov-Bohm effect
It is shown that the molecular Aharonov-Bohm effect is neither nonlocal nor
topological in the sense of the standard magnetic Aharonov-Bohm effect. It is
further argued that there is a close relationship between the molecular
Aharonov-Bohm effect and the Aharonov-Casher effect for an electrically neutral
spin particle encircling a line of charge.Comment: 3 pages, no figure
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