31,421 research outputs found
Implementing global constraints as graphs of elementary constraints
Global constraints are cardinal concepts of CLP (FD), a constraint programming language. They are means to find a set of integers that satisfy certain relations. The fact that defining global constraints often requires the knowledge of a specification language makes sharing constraints between scientists and programmers difficult. Nicolas Beldiceanu presented a theory that could solve this problem, because it depicts global constraints as graphs: an abstraction that everyone understands. The abstract description language defined by the theory may also be interpreted by a computer program. This paper deals with the problematic issues of putting the theory into practice by implementing such a program. It introduces a concrete syntax of the language and presents three programs understanding that syntax. These case studies represent two different approaches of propagation. One of these offers exhausting pruning with poor efficiency, the other, yet unfinished attempt provides a better alternative at the cost of being a lot more complicated
A Local Search Modeling for Constrained Optimum Paths Problems (Extended Abstract)
Constrained Optimum Path (COP) problems appear in many real-life
applications, especially on communication networks. Some of these problems have
been considered and solved by specific techniques which are usually difficult
to extend. In this paper, we introduce a novel local search modeling for
solving some COPs by local search. The modeling features the compositionality,
modularity, reuse and strengthens the benefits of Constrained-Based Local
Search. We also apply the modeling to the edge-disjoint paths problem (EDP). We
show that side constraints can easily be added in the model. Computational
results show the significance of the approach
Flexible Multi-layer Sparse Approximations of Matrices and Applications
The computational cost of many signal processing and machine learning
techniques is often dominated by the cost of applying certain linear operators
to high-dimensional vectors. This paper introduces an algorithm aimed at
reducing the complexity of applying linear operators in high dimension by
approximately factorizing the corresponding matrix into few sparse factors. The
approach relies on recent advances in non-convex optimization. It is first
explained and analyzed in details and then demonstrated experimentally on
various problems including dictionary learning for image denoising, and the
approximation of large matrices arising in inverse problems
Extended matter coupled to BF theory
Recently, a topological field theory of membrane-matter coupled to BF theory
in arbitrary spacetime dimensions was proposed [1]. In this paper, we discuss
various aspects of the four-dimensional theory. Firstly, we study classical
solutions leading to an interpretation of the theory in terms of strings
propagating on a flat spacetime. We also show that the general classical
solutions of the theory are in one-to-one correspondence with solutions of
Einstein's equations in the presence of distributional matter (cosmic strings).
Secondly, we quantize the theory and present, in particular, a prescription to
regularize the physical inner product of the canonical theory. We show how the
resulting transition amplitudes are dual to evaluations of Feynman diagrams
coupled to three-dimensional quantum gravity. Finally, we remove the regulator
by proving the topological invariance of the transition amplitudes.Comment: 27 pages, 7 figure
Outer-totalistic cellular automata on graphs
We present an intuitive formalism for implementing cellular automata on
arbitrary topologies. By that means, we identify a symmetry operation in the
class of elementary cellular automata. Moreover, we determine the subset of
topologically sensitive elementary cellular automata and find that the overall
number of complex patterns decreases under increasing neighborhood size in
regular graphs. As exemplary applications, we apply the formalism to complex
networks and compare the potential of scale-free graphs and metabolic networks
to generate complex dynamics.Comment: 5 pages, 4 figures, 1 table. To appear in Physics Letters
Design of multimedia processor based on metric computation
Media-processing applications, such as signal processing, 2D and 3D graphics
rendering, and image compression, are the dominant workloads in many embedded
systems today. The real-time constraints of those media applications have
taxing demands on today's processor performances with low cost, low power and
reduced design delay. To satisfy those challenges, a fast and efficient
strategy consists in upgrading a low cost general purpose processor core. This
approach is based on the personalization of a general RISC processor core
according the target multimedia application requirements. Thus, if the extra
cost is justified, the general purpose processor GPP core can be enforced with
instruction level coprocessors, coarse grain dedicated hardware, ad hoc
memories or new GPP cores. In this way the final design solution is tailored to
the application requirements. The proposed approach is based on three main
steps: the first one is the analysis of the targeted application using
efficient metrics. The second step is the selection of the appropriate
architecture template according to the first step results and recommendations.
The third step is the architecture generation. This approach is experimented
using various image and video algorithms showing its feasibility
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