3,726 research outputs found
Approximating Petri Net Reachability Along Context-free Traces
We investigate the problem asking whether the intersection of a context-free
language (CFL) and a Petri net language (PNL) is empty. Our contribution to
solve this long-standing problem which relates, for instance, to the
reachability analysis of recursive programs over unbounded data domain, is to
identify a class of CFLs called the finite-index CFLs for which the problem is
decidable. The k-index approximation of a CFL can be obtained by discarding all
the words that cannot be derived within a budget k on the number of occurrences
of non-terminals. A finite-index CFL is thus a CFL which coincides with its
k-index approximation for some k. We decide whether the intersection of a
finite-index CFL and a PNL is empty by reducing it to the reachability problem
of Petri nets with weak inhibitor arcs, a class of systems with infinitely many
states for which reachability is known to be decidable. Conversely, we show
that the reachability problem for a Petri net with weak inhibitor arcs reduces
to the emptiness problem of a finite-index CFL intersected with a PNL.Comment: 16 page
Covariance and Controvariance: a fresh look at an old issue (a primer in advanced type systems for learning functional programmers)
Twenty years ago, in an article titled "Covariance and contravariance:
conflict without a cause", I argued that covariant and contravariant
specialization of method parameters in object-oriented programming had
different purposes and deduced that, not only they could, but actually they
should both coexist in the same language.
In this work I reexamine the result of that article in the light of recent
advances in (sub-)typing theory and programming languages, taking a fresh look
at this old issue.
Actually, the revamping of this problem is just an excuse for writing an
essay that aims at explaining sophisticated type-theoretic concepts, in simple
terms and by examples, to undergraduate computer science students and/or
willing functional programmers.
Finally, I took advantage of this opportunity to describe some undocumented
advanced techniques of type-systems implementation that are known only to few
insiders that dug in the code of some compilers: therefore, even expert
language designers and implementers may find this work worth of reading
Statistical Assertions for Validating Patterns and Finding Bugs in Quantum Programs
In support of the growing interest in quantum computing experimentation,
programmers need new tools to write quantum algorithms as program code.
Compared to debugging classical programs, debugging quantum programs is
difficult because programmers have limited ability to probe the internal states
of quantum programs; those states are difficult to interpret even when
observations exist; and programmers do not yet have guidelines for what to
check for when building quantum programs. In this work, we present quantum
program assertions based on statistical tests on classical observations. These
allow programmers to decide if a quantum program state matches its expected
value in one of classical, superposition, or entangled types of states. We
extend an existing quantum programming language with the ability to specify
quantum assertions, which our tool then checks in a quantum program simulator.
We use these assertions to debug three benchmark quantum programs in factoring,
search, and chemistry. We share what types of bugs are possible, and lay out a
strategy for using quantum programming patterns to place assertions and prevent
bugs.Comment: In The 46th Annual International Symposium on Computer Architecture
(ISCA '19). arXiv admin note: text overlap with arXiv:1811.0544
Real time interactive graphics systems identification
“This thesis describes the implementation of an identification procedure as a package of graphic programs. This package of graphic programs will allow the user to perform a least squares parameter estimation, a recursive least squares parameter estimation, and a maximum likelihood parameter estimation of a linear second-order transfer function model. This model describes in a linear form the dynamic response of an automobile in a field operating environment.
The model is to reasonably reproduce the physical behavior of an automobile through two of its dynamic variables. These are the yaw rate as output and wheel angle as input. The model will make subsequent control designs easier to perform mathematically”--Abstract, page ii
Detection of Buried Inhomogeneous Elliptic Cylinders by a Memetic Algorithm
The application of a global optimization procedure to the detection of buried inhomogeneities is studied in the present paper. The object inhomogeneities are schematized as multilayer infinite dielectric cylinders with elliptic cross sections. An efficient recursive analytical procedure is used for the forward scattering computation. A functional is constructed in which the field is expressed in series solution of Mathieu functions. Starting by the input scattered data, the iterative minimization of the functional is performed by a new optimization method called memetic algorithm. (c) 2003 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works
Applications of optical processing for improving ERTS data, volume 1
Application of optically diagnosed noise information toward development of filtering subroutines for improvement of digital sensing data tape quality - Vol.
A Generic Approach for Escaping Saddle points
A central challenge to using first-order methods for optimizing nonconvex
problems is the presence of saddle points. First-order methods often get stuck
at saddle points, greatly deteriorating their performance. Typically, to escape
from saddles one has to use second-order methods. However, most works on
second-order methods rely extensively on expensive Hessian-based computations,
making them impractical in large-scale settings. To tackle this challenge, we
introduce a generic framework that minimizes Hessian based computations while
at the same time provably converging to second-order critical points. Our
framework carefully alternates between a first-order and a second-order
subroutine, using the latter only close to saddle points, and yields
convergence results competitive to the state-of-the-art. Empirical results
suggest that our strategy also enjoys a good practical performance
Software Engineering and Complexity in Effective Algebraic Geometry
We introduce the notion of a robust parameterized arithmetic circuit for the
evaluation of algebraic families of multivariate polynomials. Based on this
notion, we present a computation model, adapted to Scientific Computing, which
captures all known branching parsimonious symbolic algorithms in effective
Algebraic Geometry. We justify this model by arguments from Software
Engineering. Finally we exhibit a class of simple elimination problems of
effective Algebraic Geometry which require exponential time to be solved by
branching parsimonious algorithms of our computation model.Comment: 70 pages. arXiv admin note: substantial text overlap with
arXiv:1201.434
Lander Trajectory Reconstruction computer program
The Lander Trajectory Reconstruction (LTR) computer program is a tool for analysis of the planetary entry trajectory and atmosphere reconstruction process for a lander or probe. The program can be divided into two parts: (1) the data generator and (2) the reconstructor. The data generator provides the real environment in which the lander or probe is presumed to find itself. The reconstructor reconstructs the entry trajectory and atmosphere using sensor data generated by the data generator and a Kalman-Schmidt consider filter. A wide variety of vehicle and environmental parameters may be either solved-for or considered in the filter process
- …