A simple proof of a recurrence theorem for random walks in Z2\Z^{2}

In this note, we prove without using Fourier analysis that the symmetric square integrable random walks in $\Z^{2}$ are recurrent.Comment: 2 page

The Energetic Reasoning Checker Revisited

Energetic Reasoning (ER) is a powerful filtering algorithm for the Cumulative constraint. Unfortunately, ER is generally too costly to be used in practice. One reason of its bad behavior is that many intervals are considered as relevant by the checker of ER, although most of them should be ignored. In this paper, we provide a sharp characterization that allows to reduce the number of intervals by a factor seven. Our experiments show that associating this checker with a Time-Table filtering algorithm leads to promising results.Comment: CP Doctoral Program 2013, Uppsala : Sweden (2013

Fine-Grain Iterative Compilation for WCET Estimation

Compiler optimizations, although reducing the execution times of programs, raise issues in static WCET estimation techniques and tools. Flow facts, such as loop bounds, may not be automatically found by static WCET analysis tools after aggressive code optimizations. In this paper, we explore the use of iterative compilation (WCET-directed program optimization to explore the optimization space), with the objective to (i) allow flow facts to be automatically found and (ii) select optimizations that result in the lowest WCET estimates. We also explore to which extent code outlining helps, by allowing the selection of different optimization options for different code snippets of the application

Auctioned IPOs: The U.S. Evidence

Between 1999 and 2007, WR Hambrecht has completed 19 IPOs in the U.S. using an auction mechanism. We analyze investor behavior and mechanism performance in these auctioned IPOs using detailed bidding data. The existence of some bids posted at high prices suggests that some investors (mostly retail) try to free-ride on the mechanism. But institutional demand in these auctions is very elastic, suggesting that institutional investors reveal information in the bidding process. Investor participation is largely predictable based on deal size, and demand is dominated by institutions. Flipping is equally prevalent in auctions as in bookbuilt deals – but unlike in bookbuilding, investors in auctions tend to flip their shares more in cold deals. Finally, we find that institutional investors, who provide more information, are rewarded by obtaining a larger share of the deals that have higher initial returns. Our results therefore suggest that auctioned IPOs could be an effective alternative to traditional bookbuilding.Initial public offerings;investment banking;auctions

A very low latency pitch tracker for audio to midi conversion

International audienceAn algorithm for estimating the fundamental frequency of a single-pitch audio signal is described, for application to audio-to-MIDI conversion. In order to minimize latency, this method is based on the ESPRIT algorithm, together with a statistical model for partials frequencies. It is tested on real guitar recordings and compared to the YIN estimator. We show that, in this particular context, both methods exhibit a similar accuracy but the periodicity measure, used for note segmentation, is much more stable with the ESPRIT-based algorithm. This allows to significantly reduce ghost notes. This method is also able to get very close to the theoretical mini-mum latency, i.e. the fundamental period of the lowest observable pitch. Furthermore, it appears that fast implementations can reach a reasonable complexity and could be compatible with real-time, although this is not tested is this study

Strictly positive definite functions on the real line

We give some necessary or sufficient conditions for a function to be strictly positive definite on $\mathbb R$. This problem is intimately linked with the repartition of the zeros of trigonometric polynomials

Une nouvelle caractérisation des intervalles d'intérêt pour le raisonnement énergétique

National audienceLe raisonnement énergétique (ER) pour la contrainte Cumulative permet un filtrage des domaines supérieur à la plupart des algorithmes de l'état de l'art. Hélas, il est généralement trop coûteux pour être uti-lisé en pratique. Une des raisons de ce coût important est que trop d'intervalles de temps sont considérés. Dans la littérature, des approches heuristiques ont été développées dans le but de réduire le nombre d'inter-valles à considérer, entrainant une perte de filtrage. Dans cet article, nous démontrons qu'il est possible de réduire le nombre d'intervalles d'intérêt jusqu'à un fac-teur sept pour la condition d'échec et le propagateur, sans diminuer la puissance de filtrage. En outre, nous montrons que, pour certaines classes de problèmes, associer ER à un algorithme de Time-Table constitue le meilleur compromis opérationnel