64,774 research outputs found
Automatic Repair of Infinite Loops
Research on automatic software repair is concerned with the development of
systems that automatically detect and repair bugs. One well-known class of bugs
is the infinite loop. Every computer programmer or user has, at least once,
experienced this type of bug. We state the problem of repairing infinite loops
in the context of test-suite based software repair: given a test suite with at
least one failing test, generate a patch that makes all test cases pass.
Consequently, repairing infinites loop means having at least one test case that
hangs by triggering the infinite loop. Our system to automatically repair
infinite loops is called . We develop a technique to manipulate
loops so that one can dynamically analyze the number of iterations of loops;
decide to interrupt the loop execution; and dynamically examine the state of
the loop on a per-iteration basis. Then, in order to synthesize a new loop
condition, we encode this set of program states as a code synthesis problem
using a technique based on Satisfiability Modulo Theory (SMT). We evaluate our
technique on seven seeded-bugs and on seven real-bugs. is able to
repair all of them, within seconds up to one hour on a standard laptop
configuration
Linear Tabulated Resolution Based on Prolog Control Strategy
Infinite loops and redundant computations are long recognized open problems
in Prolog. Two ways have been explored to resolve these problems: loop checking
and tabling. Loop checking can cut infinite loops, but it cannot be both sound
and complete even for function-free logic programs. Tabling seems to be an
effective way to resolve infinite loops and redundant computations. However,
existing tabulated resolutions, such as OLDT-resolution, SLG- resolution, and
Tabulated SLS-resolution, are non-linear because they rely on the
solution-lookup mode in formulating tabling. The principal disadvantage of
non-linear resolutions is that they cannot be implemented using a simple
stack-based memory structure like that in Prolog. Moreover, some strictly
sequential operators such as cuts may not be handled as easily as in Prolog.
In this paper, we propose a hybrid method to resolve infinite loops and
redundant computations. We combine the ideas of loop checking and tabling to
establish a linear tabulated resolution called TP-resolution. TP-resolution has
two distinctive features: (1) It makes linear tabulated derivations in the same
way as Prolog except that infinite loops are broken and redundant computations
are reduced. It handles cuts as effectively as Prolog. (2) It is sound and
complete for positive logic programs with the bounded-term-size property. The
underlying algorithm can be implemented by an extension to any existing Prolog
abstract machines such as WAM or ATOAM.Comment: To appear as the first accepted paper in Theory and Practice of Logic
Programming (http://www.cwi.nl/projects/alp/TPLP
Markov chain sampling of the loop models on the infinite plane
It was recently proposed in
https://journals.aps.org/pre/abstract/10.1103/PhysRevE.94.043322 [Herdeiro &
Doyon Phys.,Rev.,E (2016)] a numerical method showing a precise sampling of the
infinite plane 2d critical Ising model for finite lattice subsections. The
present note extends the method to a larger class of models, namely the
loop gas models for . We argue that even though the Gibbs measure
is non local, it is factorizable on finite subsections when sufficient
information on the loops touching the boundaries is stored. Our results attempt
to show that provided an efficient Markov chain mixing algorithm and an
improved discrete lattice dilation procedure the planar limit of the
models can be numerically studied with efficiency similar to the Ising case.
This confirms that scale invariance is the only requirement for the present
numerical method to work.Comment: v2: added conclusion section, changes in introduction and appendice
Multiple time scales from hard local constraints: glassiness without disorder
While multiple time scales generally arise in the dynamics of disordered
systems, we find multiple time scales in absence of disorder, in a simple model
with hard local constraints. The dynamics of the model, which consists of local
collective rearrangements of various scales, is not determined by the smallest
scale but by a length that grows at low energies. In real space we find a
hierarchy of fast and slow regions: each slow region is geometrically insulated
from all faster degrees of freedom, which are localized in fast pockets below
percolation thresholds. A tentative analogy with structural glasses is given,
which attributes the slowing down of the dynamics to the growing size of mobile
elementary excitations, rather than to the size of some domains.Comment: 10 pages, 9 figures, v2: pub
Monte Carlo simulation of ice models
We propose a number of Monte Carlo algorithms for the simulation of ice
models and compare their efficiency. One of them, a cluster algorithm for the
equivalent three colour model, appears to have a dynamic exponent close to
zero, making it particularly useful for simulations of critical ice models. We
have performed extensive simulations using our algorithms to determine a number
of critical exponents for the square ice and F models.Comment: 32 pages including 15 postscript figures, typeset in LaTeX2e using
the Elsevier macro package elsart.cl
Cosmic String Loop Microlensing
Cosmic superstring loops within the galaxy microlens background point sources
lying close to the observer-string line of sight. For suitable alignments,
multiple paths coexist and the (achromatic) flux enhancement is a factor of
two. We explore this unique type of lensing by numerically solving for
geodesics that extend from source to observer as they pass near an oscillating
string. We characterize the duration of the flux doubling and the scale of the
image splitting. We probe and confirm the existence of a variety of fundamental
effects predicted from previous analyses of the static infinite straight
string: the deficit angle, the Kaiser-Stebbins effect, and the scale of the
impact parameter required to produce microlensing. Our quantitative results for
dynamical loops vary by O(1) factors with respect to estimates based on
infinite straight strings for a given impact parameter. A number of new
features are identified in the computed microlensing solutions. Our results
suggest that optical microlensing can offer a new and potentially powerful
methodology for searches for superstring loop relics of the inflationary era.Comment: 20 pages, 19 figure
- …