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A Simple and Tight Greedy OCRS [article]

Vasilis Livanos
2021 arXiv   pre-print
Intuitively, a greedy OCRS has to decide which elements to include in the integral solution before the online process starts.  ...  In this work, we give simple 1/e - selectable greedy OCRSs for rank-1 matroids, partition matroids and transversal matroids.  ...  Acknowledgements: The author would like to thank Chandra Chekuri and Jan Vondrák for guidance and helpful discussions.  ... 
arXiv:2111.13253v2 fatcat:zlh5kn5bdzdprexjlr3flt3d5y

On Submodular Prophet Inequalities and Correlation Gap [article]

Chandra Chekuri, Vasilis Livanos
2021 arXiv   pre-print
Rubinstein and Singla developed a notion of combinatorial prophet inequalities in order to generalize the standard prophet inequality setting to combinatorial valuation functions such as submodular and  ...  Along the way they showed a variant of the correlation gap for non-negative submodular functions.  ...  CC thanks Vondrák and VL thanks Maria Siskaki, Kesav Krishnan and Venkata Sai Bavisetty for helpful discussions.  ... 
arXiv:2107.03662v1 fatcat:r6eazxwdtbannmlkz5gxvvk5ta

Online Stochastic Max-Weight Matching: prophet inequality for vertex and edge arrival models [article]

Tomer Ezra, Michal Feldman, Nick Gravin, Zhihao Gavin Tang
2020 arXiv   pre-print
We first extend the framework of OCRS to batched-OCRS, we then establish a reduction from batched prophet inequality to batched OCRS, and finally we construct batched OCRSs with selectable ratios of 0.337  ...  For the vertex arrival, our result is tight. Interestingly, a pricing-based prophet inequality with comparable competitive ratios is unknown.  ...  For such a sampling scheme R one can achieve a pretty good c-selectable OCRS with c " 17 20 , by following a simple greedy algorithm that includes as many elements from R t into a feasible set I as it  ... 
arXiv:2002.09807v2 fatcat:nvoue6y6nbag3nyg3bsk6j27xm

Submodular Dominance and Applications [article]

Frederick Qiu, Sahil Singla
2022 arXiv   pre-print
We introduce a natural notion of negative dependence, which we call Weak Negative Regression (WNR), that generalizes both Negative Association and Negative Regression.  ...  In submodular optimization we often deal with the expected value of a submodular function f on a distribution 𝒟 over sets of elements.  ...  underlying greedy OCRS π I, x and the adversarial ordering of the items.  ... 
arXiv:2207.04957v1 fatcat:mflbhtxelval5fmkhnvi6pl6ce

Combinatorial Prophet Inequalities [article]

Aviad Rubinstein, Sahil Singla
2016 arXiv   pre-print
Even for the special case of a cardinality feasibility constraint, our algorithm circumvents an Ω(√(n)) lower bound by Bateni, Hajiaghayi, and Zadimoghaddam BHZ13-submodular-secretary_original in a restricted  ...  En route to our submodular prophet inequality, we prove a technical result of independent interest: we show a variant of the Correlation Gap Lemma for non-monotone submodular functions.  ...  Definition 3.7 (Greedy OCRS). Let x belong to a matroid polytope P and S ∼ x. A greedy OCRS defines a downward-closed family F x of feasible sets in the matroid.  ... 
arXiv:1611.00665v1 fatcat:qdks4q6gq5fr7dc7wocdlllckm

Improved Online Contention Resolution for Matchings and Applications to the Gig Economy [article]

Tristan Pollner, Mohammad Roghani, Amin Saberi, David Wajc
2022 arXiv   pre-print
Our main result is a 0.456-balanced RO-OCRS in bipartite graphs and a 0.45-balanced RO-OCRS in general graphs.  ...  As a consequence of our OCRS results, we obtain a 0.456-approximate algorithm for the sequential pricing problem.  ...  Warm-Up : A 1 2 (1 − e −2 )-balanced RO-OCRS We start by presenting a simple instantiation of Algorithm 2 yielding a 1 2 (1−e −2 ) ≈ 0.432-balanced RO-OCRS for matching in general graphs.  ... 
arXiv:2205.08667v1 fatcat:qrkdooc2knezpeuys7b2jsynsu

Optimal Online Contention Resolution Schemes via Ex-Ante Prophet Inequalities

Euiwoong Lee, Sahil Singla, Michael Wagner
2018 European Symposium on Algorithms  
We design the first optimal 1/2-OCRS for matroids by reducing the problem to designing a matroid prophet inequality where we compare to the stronger benchmark of an ex-ante relaxation.  ...  Online contention resolution schemes (OCRSs) were proposed by Feldman, Svensson, and Zenklusen [11] as a generic technique to round a fractional solution in the matroid polytope in an online fashion.  ...  The second author was supported in part by NSF awards CCF-1319811, CCF-1536002, and CCF-1617790.  ... 
doi:10.4230/lipics.esa.2018.57 dblp:conf/esa/LeeS18 fatcat:as22magtlvgbznq6ihpcjiqtoi

Optimal Online Contention Resolution Schemes via Ex-Ante Prophet Inequalities [article]

Euiwoong Lee, Sahil Singla
2018 arXiv   pre-print
Online contention resolution schemes (OCRSs) were proposed by Feldman, Svensson, and Zenklusen as a generic technique to round a fractional solution in the matroid polytope in an online fashion.  ...  We design the first optimal 1/2-OCRS for matroids by reducing the problem to designing a matroid prophet inequality where we compare to the stronger benchmark of an ex-ante relaxation.  ...  We are thankful to Ravishankar Krishnaswamy and Deeparnab Chakrabarty for useful discussions in early part of this project.  ... 
arXiv:1806.09251v1 fatcat:q3k3lx6e6fevtlfyqxszuczjnq

Delegated Stochastic Probing [article]

Curtis Bechtel, Shaddin Dughmi
2020 arXiv   pre-print
We also explore randomized mechanisms in a simple delegated probing setting, and show that they outperform deterministic mechanisms in some instances but not in the worst case.  ...  In this work, we combine the concepts of delegation and stochastic probing into a single mechanism design framework which we term delegated stochastic probing.  ...  We note that there is an open question about the existence of 1 2 -OCRS for matroids against the almighty adversary [21] , and the existence of such an OCRS, if greedy, would imply the existence of 1  ... 
arXiv:2010.14718v2 fatcat:2vferkfxzvdrvjimctxzm4mxtm

Supervised template estimation for document image decoding

G.E. Kopec, M. Lomelin
1997 IEEE Transactions on Pattern Analysis and Machine Intelligence  
This leads to a three-phase iterative training algorithm consisting of transcription alignment, aligned template estimation (ATE) and channel estimation steps.  ...  An approach to supervised training of character templates from page images and unaligned transcriptions is proposed.  ...  Fig. 5 shows a simple greedy pixel coloring algorithm that is useful by itself and also forms the basis for more sophisticated algorithms.  ... 
doi:10.1109/34.643891 fatcat:y7la35gon5dwle4uuy7vfwjph4

A Stochastic Approach to Hierarchical Planning and Scheduling [chapter]

M. A. H. Dempster
1982 Deterministic and Stochastic Scheduling  
It continues recent trends in IIASA research which concern studies of hierarchical systems and optimization of stochastic systems and is a sequel to two earlier papers RR-84-4 and RR-84-5.  ...  A 3-level location, distribution and routing model in the plane is also discussed. l itJ l~J. : \ . It. Lii 1\<U .Jt LI"\  ...  I am indebted to my colleagues for stimulating discussions and for providing me with manuscripts of work in progress which permitted this attempt at a comprehensive survey of our collective effort.  ... 
doi:10.1007/978-94-009-7801-0_15 fatcat:fystbnva4rflfbphjm5z4sekty

Extraction of special effects caption text events from digital video

David Crandall, Sameer Antani, Rangachar Kasturi
2003 International Journal on Document Analysis and Recognition  
One approach is to extract text appearing in video, which often reflects a scene's semantic content. This is a difficult problem due to the unconstrained nature of general-purpose video.  ...  Text can have arbitrary color, size, and orientation. Backgrounds may be complex and changing. Most work so far has made restrictive assumptions about the nature of text occurring in video.  ...  Video text extraction vs. document OCR At first, extraction of text from video may seem to be a simple extension of existing optical character recognition (OCR) problems.  ... 
doi:10.1007/s10032-002-0091-7 fatcat:fatw7sg7tjhp3em5qqc34ft5gi

On Multi-Dimensional Gains from Trade Maximization [article]

Yang Cai, Kira Goldner, Steven Ma, Mingfei Zhao
2022 arXiv   pre-print
Specifically, we focus on a setting with n heterogeneous items, where each item is owned by a different seller i, and there is a constrained-additive buyer with feasibility constraint ℱ.  ...  In addition, single-dimensional settings in two-sided markets, e.g. where a buyer and seller each seek or own a single item, are also well-understood.  ...  Suppose there exist a (δ, η 1 )-selectable greedy OCRS π 1 for P 1 and F 1 , and a (δ, η 2 )-selectable greedy OCRS π 2 for P 2 and F 2 .  ... 
arXiv:2007.13934v2 fatcat:e7fc3tc44ne7vfdvc6ftcgwwuq

A conditional random field approach for audio-visual people diarization

Gay Paul, Khoury Elie, Meignier Sylvain, Odobez Jean-Marc, Deleglise Paul
2014 2014 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP)  
and visual streams using a set of AV cues and their association strength.  ...  First, we formulate the problem within a novel CRF framework that simultaneously performs the AV association of voices and face clusters to build AV person models, and the joint segmentation of the audio  ...  The authors gratefully acknowledge the financial support from the French Research Agency (ANR) under the Project SODA and from the European Union under the EUMSSI project (grant agreement 611057).  ... 
doi:10.1109/icassp.2014.6853569 dblp:conf/icassp/GayKMOD14 fatcat:r3dwb3xhprbo3iem7bpez6faum

Non-Adaptive Matroid Prophet Inequalities [article]

Shuchi Chawla, Kira Goldner, Anna R. Karlin, J. Benjamin Miller
2020 arXiv   pre-print
Matroid prophet inequalities have been considered resolved since 2012 when [KW12] introduced thresholds that guarantee a tight 2-approximation to the prophet; however, this algorithm is adaptive.  ...  A major application of prophet inequalities is in auction design, where non-adaptive prices possess a significant advantage: they convert to order-oblivious posted pricings, and are essential for translating  ...  If such an approach were to work, we could convert any non-adaptive matroid prophet inequality to a prophet inequality, as a greedy OCRS exists for all matroids and constructs constrained non-adaptive  ... 
arXiv:2011.09406v1 fatcat:lpnskuotvvcqziodpyyizmzkpy
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