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Learning Augmented Energy Minimization via Speed Scaling [article]

Étienne Bamas, Andreas Maggiori, Lars Rohwedder, Ola Svensson
2020 arXiv   pre-print
As power management has become a primary concern in modern data centers, computing resources are being scaled dynamically to minimize energy consumption. We initiate the study of a variant of the classic online speed scaling problem, in which machine learning predictions about the future can be integrated naturally. Inspired by recent work on learning-augmented online algorithms, we propose an algorithm which incorporates predictions in a black-box manner and outperforms any online algorithm if
more » ... the accuracy is high, yet maintains provable guarantees if the prediction is very inaccurate. We provide both theoretical and experimental evidence to support our claims.
arXiv:2010.11629v1 fatcat:wfhjel2mxbehxozxs5s4tn2sg4

The Primal-Dual method for Learning Augmented Algorithms [article]

Étienne Bamas, Andreas Maggiori, Ola Svensson
2020 arXiv   pre-print
The extension of classical online algorithms when provided with predictions is a new and active research area. In this paper, we extend the primal-dual method for online algorithms in order to incorporate predictions that advise the online algorithm about the next action to take. We use this framework to obtain novel algorithms for a variety of online covering problems. We compare our algorithms to the cost of the true and predicted offline optimal solutions and show that these algorithms
more » ... form any online algorithm when the prediction is accurate while maintaining good guarantees when the prediction is misleading.
arXiv:2010.11632v1 fatcat:q5ttej25wba5leobp3gcaucg4a

An Improved Analysis of Greedy for Online Steiner Forest [article]

Étienne Bamas, Marina Drygala, Andreas Maggiori
2021 arXiv   pre-print
This paper considers the classic Online Steiner Forest problem where one is given a (weighted) graph G and an arbitrary set of k terminal pairs {{s_1,t_1},... ,{s_k,t_k}} that are required to be connected. The goal is to maintain a minimum-weight sub-graph that satisfies all the connectivity requirements as the pairs are revealed one by one. It has been known for a long time that no algorithm (even randomized) can be better than Ω(log(k))-competitive for this problem. Interestingly, a simple
more » ... edy algorithm is already very efficient for this problem. This algorithm can be informally described as follows: Upon arrival of a new pair {s_i,t_i}, connect s_i and t_i with the shortest path in the current metric, contract the metric along the chosen path and wait for the next pair. Although simple and intuitive, greedy proved itself challenging to analyze and its competitive ratio is a long-standing open problem in the area of online algorithms. The last progress on this question is due to an elegant analysis by Awerbuch, Azar, and Bartal [SODA 1996], who showed that greedy is O(log^2(k))-competitive. Our main result is to show that greedy is in fact O(log(k)loglog(k))-competitive on a wide class of instances. In particular, this wide class of instances contains all the instances that were exhibited in the literature until now.
arXiv:2111.10086v1 fatcat:ghesp2fkcrhihaqnrjay6vhtjm

The Submodular Santa Claus Problem in the Restricted Assignment Case [article]

Etienne Bamas, Paritosh Garg, Lars Rohwedder
2020 arXiv   pre-print
The submodular Santa Claus problem was introduced in a seminal work by Goemans, Harvey, Iwata, and Mirrokni (SODA'09) as an application of their structural result. In the mentioned problem n unsplittable resources have to be assigned to m players, each with a monotone submodular utility function f_i. The goal is to maximize min_i f_i(S_i) where S_1,...,S_m is a partition of the resources. The result by Goemans et al. implies a polynomial time O(n^1/2 +ε)-approximation algorithm. Since then
more » ... ess on this problem was limited to the linear case, that is, all f_i are linear functions. In particular, a line of research has shown that there is a polynomial time constant approximation algorithm for linear valuation functions in the restricted assignment case. This is the special case where each player is given a set of desired resources Γ_i and the individual valuation functions are defined as f_i(S) = f(S ∩Γ_i) for a global linear function f. This can also be interpreted as maximizing min_i f(S_i) with additional assignment restrictions, i.e., resources can only be assigned to certain players. In this paper we make comparable progress for the submodular variant. Namely, if f is a monotone submodular function, we can in polynomial time compute an O(loglog(n))-approximate solution.
arXiv:2011.06939v1 fatcat:qh4ysuy2ufcg3cwvqowiy6mkwa

A Simple LP-Based Approximation Algorithm for the Matching Augmentation Problem [article]

Etienne Bamas, Marina Drygala, Ola Svensson
2022 arXiv   pre-print
The Matching Augmentation Problem (MAP) has recently received significant attention as an important step towards better approximation algorithms for finding cheap 2-edge connected subgraphs. This has culminated in a 5/3-approximation algorithm. However, the algorithm and its analysis are fairly involved and do not compare against the problem's well-known LP relaxation called the cut LP. In this paper, we propose a simple algorithm that, guided by an optimal solution to the cut LP, first selects
more » ... a DFS tree and then finds a solution to MAP by computing an optimum augmentation of this tree. Using properties of extreme point solutions, we show that our algorithm always returns (in polynomial time) a better than 2-approximation when compared to the cut LP. We thereby also obtain an improved upper bound on the integrality gap of this natural relaxation.
arXiv:2202.07283v1 fatcat:dmf7otvyevflhdb342sw4ehsoe

Deciphering the Roles of BamB and Its Interaction with BamA in Outer Membrane Biogenesis, T3SS Expression and Virulence in Salmonella

Fatémeh Namdari, Genaro Alejandro Hurtado-Escobar, Nadia Abed, Jérôme Trotereau, Yann Fardini, Etienne Giraud, Philippe Velge, Isabelle Virlogeux-Payant, Rajeev Misra
2012 PLoS ONE  
In E. coli, this protein has been shown to interact directly with BamA.  ...  Moreover, the results obtained with a D229A BamB variant, which is unable to immunoprecipitate BamA, suggest that the interaction of BamB with BamA is not absolutely necessary for BamB function in outer-membrane  ...  We also thank Dr Lloubes, Dr Malinverni and Dr Silhavy for providing the anti-OmpA and anti-BamA antisera respectively. Author Contributions  ... 
doi:10.1371/journal.pone.0046050 pmid:23144780 pmcid:PMC3489874 fatcat:tjx62tcyozhevibpsdzzb3fxue

Local approximation of the Maximum Cut in regular graphs [article]

Étienne Bamas, Louis Esperet
2020 arXiv   pre-print
ÉTIENNE BAMAS AND LOUIS ESPERET Let E 1 be the set of edges directed from V + ∩ S 0 to V + ∩ U 0 , or from V − ∩ U 0 to V − ∩ S 0 .  ...  ÉTIENNE BAMAS AND LOUIS ESPERET A B C D d+1 4d d+1 4d d−1 4d d−1 4d 1 2 (d−1) 2 8d (d−1) 2 8d d 2 −1 8d d 2 −1 8d V + V − V − V + To overcome this issue and close the gap with the 2 d bound, one might  ... 
arXiv:1902.04899v3 fatcat:dwk5wmdigre7jahylcucmq2ywa

Distributed Coloring of Graphs with an Optimal Number of Colors

Étienne Bamas, Louis Esperet, Michael Wagner
2019 Symposium on Theoretical Aspects of Computer Science  
Bamas and L.  ...  Bamas and L.  ... 
doi:10.4230/lipics.stacs.2019.10 dblp:conf/stacs/BamasE19 fatcat:5xof5keti5fljgbte5oevinpjm

Distributed coloring of graphs with an optimal number of colors [article]

Étienne Bamas, Louis Esperet
2019 arXiv   pre-print
This paper studies sufficient conditions to obtain efficient distributed algorithms coloring graphs optimally (i.e. with the minimum number of colors) in the LOCAL model of computation. Most of the work on distributed vertex coloring so far has focused on coloring graphs of maximum degree Δ with at most Δ+1 colors (or Δ colors when some simple obstructions are forbidden). When Δ is sufficiently large and c>Δ-k_Δ+1, for some integer k_Δ≈√(Δ)-2, we give a distributed algorithm that given a
more » ... able graph G of maximum degree Δ, finds a c-coloring of G in {O((Δ)^1/12 n), 2^O(Δ+√( n))} rounds, with high probability. The lower bound Δ-k_Δ+1 is best possible in the sense that for infinitely many values of Δ, we prove that when χ(G)<Δ -k_Δ, finding an optimal coloring of G requires Ω(n) rounds. Our proof is a light adaptation of a remarkable result of Molloy and Reed, who proved that for Δ large enough, for any c>Δ - k_Δ deciding whether χ(G)< c is in P, while Embden-Weinert et al. proved that for c<Δ-k_Δ-1, the same problem is NP-complete. Note that the sequential and distributed thresholds differ by one. We also show that for any sufficiently large Δ, and Ω(Δ)< k <Δ/100, every graph of maximum degree Δ and clique number at most Δ-k can be efficiently colored with at most Δ-ε k colors, for some absolute constant ε >0, with a randomized algorithm running in O( n/ n) rounds with high probability.
arXiv:1809.08140v3 fatcat:hbiyoszdynf7rbcf2xswnkamji

The Combinatorial Santa Claus Problem or: How to Find Good Matchings in Non-Uniform Hypergraphs [article]

Etienne Bamas, Paritosh Garg, Lars Rohwedder
2020 arXiv   pre-print
We consider hypergraphs on vertices P∪ R where each hyperedge contains exactly one vertex in P. Our goal is to select a matching that covers all of P, but we allow each selected hyperedge to drop all but an (1/α)-fraction of its intersection with R (thus relaxing the matching constraint). Here α is to be minimized. We dub this problem the Combinatorial Santa Claus problem, since we show in this paper that this problem and the Santa Claus problem are almost equivalent in terms of their
more » ... ility. The non-trivial observation that any uniform regular hypergraph admits a relaxed matching for α = O(1) was a major step in obtaining a constant approximation rate for a special case of the Santa Claus problem, which received great attention in literature. It is natural to ask if the uniformity condition can be omitted. Our main result is that every (non-uniform) regular hypergraph admits a relaxed matching for α = O(loglog(|R|)), when all hyperedges are sufficiently large (a condition that is necessary). In particular, this implies an O(loglog(|R|))-approximation algorithm for the Combinatorial Santa Claus problem with large hyperedges.
arXiv:2007.09116v2 fatcat:fz45a4smiza5fbqfh3jg3c2eh4

SERB, a nano-satellite dedicated to the Earth-Sun relationship

Mustapha Meftah, Étienne Bamas, Pierre Cambournac, Philippe Cherabier, Romain Demarets, Gaspard Denis, Axel Dion, Raphaël Duroselle, Florence Duveiller, Laetitia Eichner, Dimitri Lozeve, Guillaume Mestdagh (+11 others)
2016 Sensors and Systems for Space Applications IX  
The Solar irradiance and Earth Radiation Budget (SERB) mission is an innovative proof-of-concept nanosatellite, with three ambitious scientific objectives. The nano-satellite aims at measuring on the same platform the absolute value of the total solar irradiance (TSI) and its variability, the ultraviolet (UV) solar spectral variability, and the different components of the Earth radiation budget. SERB is a joint project between CNES (Centre National d'Études Spatiales),École polytechnique, and
more » ... TMOS (Laboratoire Atmosphères, Milieux, Observations Spatiales) scheduled for a launch in 2020-2021. It is a three-unit CubeSat (X-CubeSat II), developed by students fromÉcole polytechnique. Critical components of instrumental payloads of future large missions (coatings, UV filters, etc.) can acquire the technical maturity by flying in a CubeSat. Nano-satellites also represent an excellent alternative for instrumentation testing, allowing for longer flights than rockets. Moreover, specific scientific experiments can be performed by nano-satellites. This paper is intended to present the SERB mission and its scientific objectives.
doi:10.1117/12.2222660 fatcat:dyskj4qv25c6tk5e4gnn6l7stm

The Submodular Santa Claus Problem in the Restricted Assignment Case

Etienne Bamas, Paritosh Garg, Lars Rohwedder, Nikhil Bansal, Emanuela Merelli, James Worrell
Bamas, P. Garg, and L.  ...  Bamas, P. Garg, and L. Rohwedder 22:9 The proof of Theorem 6 is organized as follows.  ... 
doi:10.4230/lipics.icalp.2021.22 fatcat:24iijzykojed3exsikxerhrjjq

Page 143 of The Journal of Southern History Vol. 13, Issue 1 [page]

1947 The Journal of Southern History  
., of Ala- bama; the diary, 1828-1856, of William Proctor Gould, of Alabama; the au- tobiography, 1868, of Eliza Williams Chotard (Mrs. William P.  ...  Heustis, of South Carolina and Ala- bama. Typed, filmed, and photostated material as follows has been acquired: letters and diary, 1859-1863, of Lucy (Mrs.  ... 

Page 140 of National Union Catalog Vol. 6, Issue [page]

1953 National Union Catalog  
Top ist) Operas—Librettos, La Chabeaussiére, Auguste Etienne Xavier Poisson de, 1752-1820. Gulistan. 1. Etienne, Charles Guil- laume, 1777-1845. Gulistan. 11. Title.  ...  ., a of Public Administration, University of Ala- bama, 19: 66, (6; p. *" Bibliography : p. Municipal ALS! beyond corporate limits—Alabama. 1. Title.  ... 

Page 944 of Engineering and Mining Journal Vol. 115, Issue 21 [page]

1923 Engineering and Mining Journal  
Etienne A. Ritter is making mine ex- aminations at Redcliff and Whitepine, Colo. E. W. Engelmann has returned from an inspection trip to the Braden Copper. Co., in Chile. Walter L.  ...  Fellowships at University of Alabama The School of Mines of the College of Engineering of the University of Ala- bama offers five fellowships in mining and metallurgical research in co-oper- ation with  ... 
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