3,475 research outputs found
The tropical double description method
We develop a tropical analogue of the classical double description method
allowing one to compute an internal representation (in terms of vertices) of a
polyhedron defined externally (by inequalities). The heart of the tropical
algorithm is a characterization of the extreme points of a polyhedron in terms
of a system of constraints which define it. We show that checking the
extremality of a point reduces to checking whether there is only one minimal
strongly connected component in an hypergraph. The latter problem can be solved
in almost linear time, which allows us to eliminate quickly redundant
generators. We report extensive tests (including benchmarks from an application
to static analysis) showing that the method outperforms experimentally the
previous ones by orders of magnitude. The present tools also lead to worst case
bounds which improve the ones provided by previous methods.Comment: 12 pages, prepared for the Proceedings of the Symposium on
Theoretical Aspects of Computer Science, 2010, Nancy, Franc
Tropical polar cones, hypergraph transversals, and mean payoff games
We discuss the tropical analogues of several basic questions of convex
duality. In particular, the polar of a tropical polyhedral cone represents the
set of linear inequalities that its elements satisfy. We characterize the
extreme rays of the polar in terms of certain minimal set covers which may be
thought of as weighted generalizations of minimal transversals in hypergraphs.
We also give a tropical analogue of Farkas lemma, which allows one to check
whether a linear inequality is implied by a finite family of linear
inequalities. Here, the certificate is a strategy of a mean payoff game. We
discuss examples, showing that the number of extreme rays of the polar of the
tropical cyclic polyhedral cone is polynomially bounded, and that there is no
unique minimal system of inequalities defining a given tropical polyhedral
cone.Comment: 27 pages, 6 figures, revised versio
Design and Experimentation of a Large Scale Distributed Stochastic Control Algorithm Applied to Energy Management Problems
The Stochastic Dynamic Programming method often used to solve some stochastic optimization problems is only usable in low dimension, being plagued by the curse of dimensionality. In this article, we explain how to postpone this limit by using High Performance Computing: parallel and distributed algorithms design, optimized implementations and usage of large scale distributed architectures (PC clusters and Blue Gene/P)
Exposição e intoxicação por naftaleno e paradiclorobenzeno, avaliação da gravidade em uma série de casos
Trabalho de Conclusão de Curso - Universidade Federal de Santa Catarina. Curso de Medicina. Departamento de Saúde Pública
CANU-ReID: A Conditional Adversarial Network for Unsupervised person Re-IDentification
Unsupervised person re-ID is the task of identifying people on a target data
set for which the ID labels are unavailable during training. In this paper, we
propose to unify two trends in unsupervised person re-ID: clustering &
fine-tuning and adversarial learning. On one side, clustering groups training
images into pseudo-ID labels, and uses them to fine-tune the feature extractor.
On the other side, adversarial learning is used, inspired by domain adaptation,
to match distributions from different domains. Since target data is distributed
across different camera viewpoints, we propose to model each camera as an
independent domain, and aim to learn domain-independent features.
Straightforward adversarial learning yields negative transfer, we thus
introduce a conditioning vector to mitigate this undesirable effect. In our
framework, the centroid of the cluster to which the visual sample belongs is
used as conditioning vector of our conditional adversarial network, where the
vector is permutation invariant (clusters ordering does not matter) and its
size is independent of the number of clusters. To our knowledge, we are the
first to propose the use of conditional adversarial networks for unsupervised
person re-ID. We evaluate the proposed architecture on top of two
state-of-the-art clustering-based unsupervised person re-identification (re-ID)
methods on four different experimental settings with three different data sets
and set the new state-of-the-art performance on all four of them. Our code and
model will be made publicly available at
https://team.inria.fr/perception/canu-reid/
- …