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We study the efficient PAC learnability of halfspaces in the presence of Tsybakov noise. In the Tsybakov noise model, each label is independently flipped with some probability which is controlled by an adversary. This noise model…

Machine Learning · Computer Science 2020-06-12 Ilias Diakonikolas , Vasilis Kontonis , Christos Tzamos , Nikos Zarifis

We study exact active learning of binary and multiclass classifiers with margin. Given an $n$-point set $X \subset \mathbb{R}^m$, we want to learn any unknown classifier on $X$ whose classes have finite strong convex hull margin, a new…

Machine Learning · Computer Science 2022-09-12 Marco Bressan , Nicolò Cesa-Bianchi , Silvio Lattanzi , Andrea Paudice , Maximilian Thiessen

Graph Neural Networks (GNNs) exploit signals from node features and the input graph topology to improve node classification task performance. However, these models tend to perform poorly on heterophilic graphs, where connected nodes have…

Machine Learning · Computer Science 2021-12-08 Vijay Lingam , Chanakya Ekbote , Manan Sharma , Rahul Ragesh , Arun Iyer , Sundararajan Sellamanickam

Let $f:\{-1,1\}^n$ be a polynomial with at most $s$ non-zero real coefficients. We give an algorithm for exactly reconstructing f given random examples from the uniform distribution on $\{-1,1\}^n$ that runs in time polynomial in $n$ and…

Machine Learning · Computer Science 2014-11-10 Murat Kocaoglu , Karthikeyan Shanmugam , Alexandros G. Dimakis , Adam Klivans

We study the problem of PAC learning homogeneous halfspaces in the presence of Tsybakov noise. In the Tsybakov noise model, the label of every sample is independently flipped with an adversarially controlled probability that can be…

Machine Learning · Computer Science 2020-10-06 Ilias Diakonikolas , Daniel M. Kane , Vasilis Kontonis , Christos Tzamos , Nikos Zarifis

Many popular learning algorithms (E.g. Regression, Fourier-Transform based algorithms, Kernel SVM and Kernel ridge regression) operate by reducing the problem to a convex optimization problem over a vector space of functions. These methods…

Machine Learning · Computer Science 2014-05-13 Amit Daniely , Nati Linial , Shai Shalev-Shwartz

This paper is concerned with computationally efficient learning of homogeneous sparse halfspaces in $\mathbb{R}^d$ under noise. Though recent works have established attribute-efficient learning algorithms under various types of label noise…

Machine Learning · Statistics 2021-03-03 Jie Shen , Chicheng Zhang

We prove the following strong hardness result for learning: Given a distribution of labeled examples from the hypercube such that there exists a monomial consistent with $(1-\eps)$ of the examples, it is NP-hard to find a halfspace that is…

Computational Complexity · Computer Science 2010-12-06 Vitaly Feldman , Venkatesan Guruswami , Prasad Raghavendra , Yi Wu

We study convexity properties of graphs. In this paper we present a linear-time algorithm for the geodetic number in tree-cographs. Settling a 10-year-old conjecture, we prove that the Steiner number is at least the geodetic number in…

Discrete Mathematics · Computer Science 2015-09-17 Wing-Kai Hon , Ton Kloks , Hsiang-Hsuan Liu , Hung-Lung Wang , Yue-Li Wang

A set of vertices $S$ of a graph $G$ is $monophonically \ convex$ if every induced path joining two vertices of $S$ is contained in $S$. The $monophonic \ convex \ hull$ of $S$, $\langle S \rangle$, is the smallest monophonically convex set…

Discrete Mathematics · Computer Science 2023-06-22 Mitre C. Dourado , Vitor S. Ponciano , Rômulo L. O. da Silva

In a semi-supervised learning scenario, (possibly noisy) partially observed labels are used as input to train a classifier, in order to assign labels to unclassified samples. In this paper, we study this classifier learning problem from a…

Machine Learning · Computer Science 2017-07-21 Gene Cheung , Weng-Tai Su , Yu Mao , Chia-Wen Lin

We present path2vec, a new approach for learning graph embeddings that relies on structural measures of pairwise node similarities. The model learns representations for nodes in a dense space that approximate a given user-defined graph…

Computation and Language · Computer Science 2019-04-15 Andrey Kutuzov , Mohammad Dorgham , Oleksiy Oliynyk , Chris Biemann , Alexander Panchenko

The general position problem in graph theory asks for the largest set $S$ of vertices of a graph $G$ such that no shortest path of $G$ contains more than two vertices of $S$. In this paper we consider a variant of the general position…

Combinatorics · Mathematics 2022-12-15 Elias John Thomas , S. V. Ullas Chandran , James Tuite , Gabriele Di Stefano

Let $B=(X,Y,E)$ be a bipartite graph. A half-square of $B$ has one color class of $B$ as vertex set, say $X$; two vertices are adjacent whenever they have a common neighbor in $Y$. Every planar graph is a half-square of a planar bipartite…

Discrete Mathematics · Computer Science 2018-04-18 Hoang-Oanh Le , Van Bang Le

We give a polynomial-time algorithm for learning high-dimensional halfspaces with margins in $d$-dimensional space to within desired TV distance when the ambient distribution is an unknown affine transformation of the $d$-fold product of an…

Machine Learning · Computer Science 2023-11-03 Xinyuan Cao , Santosh S. Vempala

We give an algorithm that learns arbitrary Boolean functions of $k$ arbitrary halfspaces over $\mathbb{R}^n$, in the challenging distribution-free Probably Approximately Correct (PAC) learning model, running in time $2^{\sqrt{n} \cdot (\log…

Data Structures and Algorithms · Computer Science 2026-03-10 Josh Alman , Shyamal Patel , Rocco A. Servedio

In this paper we revisit some classic problems on classification under misspecification. In particular, we study the problem of learning halfspaces under Massart noise with rate $\eta$. In a recent work, Diakonikolas, Goulekakis, and Tzamos…

Machine Learning · Computer Science 2023-09-21 Sitan Chen , Frederic Koehler , Ankur Moitra , Morris Yau

We investigate the computational efficiency of multitask learning of Boolean functions over the $d$-dimensional hypercube, that are related by means of a feature representation of size $k \ll d$ shared across all tasks. We present a…

Machine Learning · Computer Science 2022-09-08 Konstantina Bairaktari , Guy Blanc , Li-Yang Tan , Jonathan Ullman , Lydia Zakynthinou

We study the problem of PAC learning $\gamma$-margin halfspaces in the presence of Massart noise. Without computational considerations, the sample complexity of this learning problem is known to be $\widetilde{\Theta}(1/(\gamma^2…

Machine Learning · Computer Science 2025-01-17 Ilias Diakonikolas , Nikos Zarifis

We study the problem of agnostically learning halfspaces which is defined by a fixed but unknown distribution $\mathcal{D}$ on $\mathbb{Q}^n\times \{\pm 1\}$. We define $\mathrm{Err}_{\mathrm{HALF}}(\mathcal{D})$ as the least error of a…

Computational Complexity · Computer Science 2016-03-15 Amit Daniely