Ravid Cohen

dblp:236/6152 · DBLP profile ↗
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3ranked-venue papers
0as first author
2since 2021 · last 2023
—ORCID · conflict

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Theory of computation · 2 · 1 since 2021Databases, data management, data science and information retrieval · 1 · 1 since 2021
YearPublicationVenuePosition
2023 Visual Representation for Capturing Creator Theme in Brand-Creator Marketplace
abstract
Providing cold start recommendations in a brand-creator marketplace is challenging as brands’ preferences extend beyond the mere objects depicted in the creator’s content and encompass the creator’s individual theme consistently thatresonates across images shared on her social media profile. Furthermore, brands often use textual keywords to describe their campaign’s aesthetic appeal, with which creators must align. To address these challenges, we propose two methods: SAME (Same Account Media Embedding), a novel creator representation employing a Siamese network to capture the unique creator theme and OAAR (Object-Agnostic Adjective Representation), enabling filtering creators based on textual adjectives that relate to aesthetic qualities through zero-shot learning. These two methods utilize CLIP, a state-of-the-art language-image model, and improve it in addressing the aforementioned challenges.
Sarel Duanis, Keren Gaiger, Ravid Cohen, Shaked Zychlinski, Asnat Greenstein-Messica
RecSys3
2022 Maintaining the Union of Unit Discs under Insertions with Near-Optimal Overhead
abstract
We present efficient dynamic data structures for maintaining the union of unit discs and the lower envelope of pseudo-lines in the plane. More precisely, we present three main results in this paper: (i) We present a linear-size data structure to maintain the union of a set of unit discs under insertions. It can insert a disc and update the union in O (( k +1)log 2 n ) time, where n is the current number of unit discs and k is the combinatorial complexity of the structural change in the union due to the insertion of the new disc. It can also compute, within the same time bound, the area of the union after the insertion of each disc. (ii) We propose a linear-size data structure for maintaining the lower envelope of a set of x -monotone pseudo-lines. It can handle insertion/deletion of a pseudo-line in O (log 2 n ) time; for a query point x 0 ∈ ℝ, it can report, in O (log n ) time, the point on the lower envelope with x -coordinate x 0 ; and for a query point q ∈ ℝ 2 , it can return all k pseudo-lines lying below q in time O (log n + k log 2 n ). (iii) We present a linear-size data structure for storing a set of circular arcs of unit radius (not necessarily on the boundary of the union of the corresponding discs), so that for a query unit disc D , all input arcs intersecting D can be reported in O ( n 1/2+ɛ + k ) time, where k is the output size and ɛ > 0 is an arbitrarily small constant. A unit-circle arc can be inserted or deleted in O (log 2 n ) time.
Pankaj K. Agarwal, Ravid Cohen, Dan Halperin, Wolfgang Mulzer
ACM Trans. Algorithms2
2019 Maintaining the Union of Unit Discs Under Insertions with Near-Optimal Overhead
abstract
We present efficient data structures for problems on unit discs and arcs of their boundary in the plane. (i) We give an output-sensitive algorithm for the dynamic maintenance of the union of n unit discs under insertions in O(k log^2 n) update time and O(n) space, where k is the combinatorial complexity of the structural change in the union due to the insertion of the new disc. (ii) As part of the solution of (i) we devise a fully dynamic data structure for the maintenance of lower envelopes of pseudo-lines, which we believe is of independent interest. The structure has O(log^2 n) update time and O(log n) vertical ray shooting query time. To achieve this performance, we devise a new algorithm for finding the intersection between two lower envelopes of pseudo-lines in O(log n) time, using tentative binary search; the lower envelopes are special in that at x=-infty any pseudo-line contributing to the first envelope lies below every pseudo-line contributing to the second envelope. (iii) We also present a dynamic range searching structure for a set of circular arcs of unit radius (not necessarily on the boundary of the union of the corresponding discs), where the ranges are unit discs, with O(n log n) preprocessing time, O(n^{1/2+epsilon} + l) query time and O(log^2 n) amortized update time, where l is the size of the output and for any epsilon>0. The structure requires O(n) storage space.
Pankaj K. Agarwal, Ravid Cohen, Dan Halperin, Wolfgang Mulzer
SoCG2