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1.
Escape analysis of object-oriented languages approximates the set of objects which do not escape from a given context. If we take a method as context, the non-escaping objects can be allocated on its activation stack;
if we take a thread, Java synchronisation locks on such objects are not needed. In this paper, we formalise a basic escape
domain
as an abstract interpretation of concrete states, which we then refine into an abstract domain
which is more concrete than
and, hence, leads to a more precise escape analysis than
. We provide optimality results for both
and
, in the form of Galois insertions from the concrete to the abstract domains and of optimal abstract operations. The Galois
insertion property is obtained by restricting the abstract domains to those elements which do not contain garbage, by using an abstract garbage collector. Our implementation of
is hence an implementation of a formally correct escape analyser, able to detect the stack allocatable creation points of
Java (bytecode) applications. 相似文献
2.
The Sum of D Small-Bias Generators Fools Polynomials of Degree D 总被引:1,自引:1,他引:0
Emanuele Viola 《Computational Complexity》2009,18(2):209-217
3.
4.
W. Hackbusch 《Computing》2007,80(2):137-168
Usually, the fast evaluation of a convolution integral
requires that the functions f, g are discretised on an equidistant grid in order to apply the fast Fourier transform. Here we discuss the efficient performance
of the convolution in locally refined grids. More precisely, the convolution result is projected into some given locally refined
grid (Galerkin approximation). Under certain conditions, the overall costs are still
where N is the sum of the dimensions of the subspaces containing f, g and the resulting function. 相似文献
5.
6.
Relations between states and maps, which are known for quantum systems in finitedimensional Hilbert spaces, are formulated
rigorously in geometrical terms with no use of coordinate (matrix) interpretation. In a tensor product realization they are
represented simply by a permutation of factors. This leads to natural generalizations for infinite-dimensional Hilbert spaces
and a simple proof of a generalized Choi Theorem. The natural framework is based on spaces of Hilbert-Schmidt operators and the corresponding tensor products of Hilbert spaces. It is proved that the corresponding isomorphisms cannot be naturally extended to compact (or bounded)
operators, nor reduced to the trace-class operators. On the other hand, it is proven that there is a natural continuous map
from trace-class operators on (with the nuclear norm) into compact operators mapping the space of all bounded operators on into trace class operators on (with the operator-norm). Also in the infinite-dimensional context, the Schmidt measure of entanglement and multipartite
generalizations of state-maps relations are considered in the paper. 相似文献
7.
8.
Remco Duits Michael Felsberg Gösta Granlund Bart ter Haar Romeny 《International Journal of Computer Vision》2007,72(1):79-102
Inspired by the early visual system of many mammalians we consider the construction of-and reconstruction from- an orientation
score
as a local orientation representation of an image,
. The mapping
is a wavelet transform
corresponding to a reducible representation of the Euclidean motion group onto
and oriented wavelet
. This wavelet transform is a special case of a recently developed generalization of the standard wavelet theory and has the
practical advantage over the usual wavelet approaches in image analysis (constructed by irreducible representations of the
similitude group) that it allows a stable reconstruction from one (single scale) orientation score. Since our wavelet transform
is a unitary mapping with stable inverse, we directly relate operations on orientation scores to operations on images in a
robust manner.
Furthermore, by geometrical examination of the Euclidean motion group
, which is the domain of our orientation scores, we deduce that an operator Φ on orientation scores must be left invariant
to ensure that the corresponding operator
on images is Euclidean invariant. As an example we consider all linear second order left invariant evolutions on orientation
scores corresponding to stochastic processes on G. As an application we detect elongated structures in (medical) images and automatically close the gaps between them.
Finally, we consider robust orientation estimates by means of channel representations, where we combine robust orientation
estimation and learning of wavelets resulting in an auto-associative processing of orientation features. Here linear averaging
of the channel representation is equivalent to robust orientation estimation and an adaptation of the wavelet to the statistics
of the considered image class leads to an auto-associative behavior of the system.
The Netherlands Organization for Scientific Research is gratefully acknowledged for financial support. This work has been
supported by EC Grant IST-2003-004176 COSPAL. 相似文献
9.
R. F. Streater 《Open Systems & Information Dynamics》2004,11(4):359-375
Let H0 be a selfadjoint operator such that Tr
is of trace class for some
, and let
denote the set of ε-bounded forms, i.e.,
for some
0 $$" align="middle" border="0">
. Let χ := Span
. Let
denote the underlying set of the quantum information manifold of states of the form
. We show that if Tr
,
Presented at the 36th Symposium on Mathematical Physics, ‘Open Systems & Quantum Information’, Toruń, Poland, June 9-12, 2004. 相似文献
1. | the map Φ,
| |
2. | The Orlicz space defined by Φ is the tangent space of at ρ0; its affine structure is defined by the (+1)-connection of Amari | |
3. | The subset of a ‘hood of ρ0, consisting of p-nearby states (those obeying for some 1$$" align="middle" border="0"> ) admits a flat affine connection known as the (-1) connection, and the span of this set is part of the cotangent space of | |
4. | These dual structures extend to the completions in the Luxemburg norms. |
10.
Agent Communication Languages (ACLs) have been developed to provide a way for agents to communicate with each other supporting
cooperation in Multi-Agent Systems (MAS). In the past few years many ACLs have been proposed for MAS and new standards are
emerging such as the ACL developed by the Foundation for Intelligent Physical Agents (FIPA). Despite these efforts, an important
issue in the research on ACLs is still open and concerns how these languages should deal with failures of agents in asynchronous MAS. The Fault Tolerant Agent Communication Language (
-
) presented in this paper addresses this issue dealing with crash failures of agents.
-
provides high-level communication primitives which support a fault-tolerant anonymous interaction protocol designed for open
MAS. We present a formal semantics for
-
and a formal specification of the underlying agent architecture. This formal framework allows us to prove that the ACL satisfies
a set of well defined knowledge-level programming requirements. To illustrate the language features we show how
-
can be effectively used to write high-level executable specifications of fault tolerant protocols, such as the Contract Net
one. 相似文献
11.
Simple a posteriori error estimators for the <Emphasis Type="Italic">h</Emphasis>-version of the boundary element method 总被引:1,自引:0,他引:1
The h-h/2-strategy is one well-known technique for the a posteriori error estimation for Galerkin discretizations of energy minimization
problems. One considers to estimate the error , where is a Galerkin solution with respect to a mesh and is a Galerkin solution with respect to the mesh obtained from a uniform refinement of . This error estimator is always efficient and observed to be also reliable in practice. However, for boundary element methods,
the energy norm is non-local and thus the error estimator η does not provide information for a local mesh-refinement. We consider Symm’s integral equation of the first kind, where the
energy space is the negative-order Sobolev space . Recent localization techniques allow to replace the energy norm in this case by some weighted L
2-norm. Then, this very basic error estimation strategy is also applicable to steer an h-adaptive algorithm. Numerical experiments in 2D and 3D show that the proposed method works well in practice. A short conclusion
is concerned with other integral equations, e.g., the hypersingular case with energy space and , respectively, or a transmission problem.
Dedicated to Professor Ernst P. Stephan on the occasion of his 60th birthday. 相似文献
12.
13.
Projection matrices from projective spaces
have long been used in multiple-view geometry to model the perspective projection created by the pin-hole camera. In this work we introduce higher-dimensional mappings
for the representation of various applications in which the world we view is no longer rigid. We also describe the multi-view constraints from these new projection matrices (where k > 3) and methods for extracting the (non-rigid) structure and motion for each application. 相似文献
14.
The generalized Zakharov system (ZS) couples a dispersive field E (scalar or vectorial) and
nondispersive fields
with a propagating speed of
. In this paper, we extend our one-dimensional time-splitting spectral method (TSSP) for the generalized ZS into higher dimension.
A main new idea is to reformulate the multi-dimensional wave equations for the nondispersive fields into a first-order system
using a change of variable defined in the Fourier space. The proposed scheme TSSP is unconditionally stable, second-order
in time and spectrally accurate in space. Moreover, in the subsonic regime, it allows numerical capturing of the subsonic
limit without resolving the small parameters
. Numerical examples confirm these properties of this method 相似文献
15.
16.
Emanuele Viola 《Computational Complexity》2005,13(3-4):147-188
We study the complexity of constructing pseudorandom generators (PRGs) from hard functions, focussing on constant-depth circuits. We show that, starting from a function
computable in alternating time O(l) with O(1) alternations that is hard on average (i.e. there is a constant
such that every circuit of size
fails to compute f on at least a 1/poly(l) fraction of inputs) we can construct a
computable by DLOGTIME-uniform constant-depth circuits of size polynomial in n. Such a PRG implies
under DLOGTIME-uniformity. On the negative side, we prove that starting from a worst-case hard function
(i.e. there is a constant
such that every circuit of size
fails to compute f on some input) for every positive constant
there is no black-box construction of a
computable by constant-depth circuits of size polynomial in n. We also study worst-case hardness amplification, which is the related problem of producing an average-case hard function starting from a worst-case hard one. In particular, we deduce that there is no blackbox worst-case hardness amplification within the polynomial time hierarchy. These negative results are obtained by showing that polynomialsize constant-depth circuits cannot compute good extractors and listdecodable codes. 相似文献
17.
Unambiguity in alternating Turing machines has received considerable attention in the context of analyzing globally unique
games by Aida et al. [ACRW] and in the design of efficient protocols involving globally unique games by Crasmaru et al. [CGRS].
This paper explores the power of unambiguity in alternating Turing machines in the following settings: 1. We show that unambiguity-based
hierarchies-AUPH, UPH, and UPH-are infinite in some relativized world. For each
, we construct another relativized world where the unambiguity-based hierarchies collapse so that they have exactly k distinct
levels and their k-th levels coincide with PSPACE. These results shed light on the relativized power of the unambiguity-based
hierarchies, and parallel the results known for the case of the polynomial hierarchy. 2. For every
, we define the bounded-level unambiguous alternating solution class UAS(k) as the class of all sets L for which there exists
a polynomial-time alternating Turing machine N, which need not be unambiguous on every input, with at most k alternations
such that
if and only if x is accepted unambiguously by N. We construct a relativized world where, for all
and
. 3. Finally, we show that robustly k-level unambiguous alternating polynomial-time Turing machines, i.e., polynomial-time
alternating Turing machines that for every oracle have k alternating levels and are unambiguous, accept languages that are
computable in
, for every oracle A. This generalizes a result of Hartmanis and Hemachandra [HH]. 相似文献
18.
We develop new techniques for the automated construction of models for subclasses of equational clausal logic. The models are represented by some specific class of rewrite rules. We show that the evaluation of arbitrary first-order formulae in these interpretations is a decidable problem. As an example of an application, we consider the class
, a decidable subclass of first-order clausal logic without equality. In the equational case,
is undecidable, but it is known to be decidable if all the equational literals are ground. We extend this result to a class of clause sets possibly containing nonground equational literals. The algorithms for extracting models from positively disconnected saturated sets proposed by Fermüller and Leitsch are extended in order to handle the full ordering restrictions of the resolution/paramodulation calculus. 相似文献
19.
Coupling and self-stabilization 总被引:1,自引:0,他引:1
A randomized self-stabilizing algorithm
is an algorithm that, whatever the initial configuration is, reaches a set
of М legal configurations} in finite time with probability 1. The proof of convergence towards
is generally done by exhibiting a potential function
, which measures the “vertical” distance of any configuration to
, such that
decreases with non-null probability at each step of
. We propose here a method, based on the notion of coupling, which makes use of a “horizontal” distance
between any pair of configurations, such that
decreases in expectation at each step of
. In contrast with classical methods, our coupling method does not require the knowledge of
. In addition to the proof of convergence, the method allows us to assess the convergence rate according to two different
measures. Proofs produced by the method are often simpler or give better upper bounds than their classical counterparts, as
examplified here on Herman's mutual exclusion and Iterated Prisoner's Dilemma algorithms in the case of cyclic graphs. 相似文献
20.
Abstract We obtain a multivariate extension of a classical result of Schoenberg on cardinal spline interpolation. Specifically, we
prove the existence of a unique function in
, polyharmonic of order p on each strip
,
, and periodic in its last n variables, whose restriction to the parallel hyperplanes
,
, coincides with a prescribed sequence of n-variate periodic data functions satisfying a growth condition in
. The constructive proof is based on separation of variables and on Micchelli’s theory of univariate cardinal
-splines.
Keywords: cardinal
-splines, polyharmonic functions, multivariable interpolation
Mathematics Subject Classification (2000): 41A05, 41A15, 41A63 相似文献