Search Results for author: Dimitris Fotakis

Found 16 papers, 3 papers with code

Efficient Online Learning of Optimal Rankings: Dimensionality Reduction via Gradient Descent

1 code implementation NeurIPS 2020 Dimitris Fotakis, Thanasis Lianeas, Georgios Piliouras, Stratis Skoulakis

We consider a natural model of online preference aggregation, where sets of preferred items $R_1, R_2, \ldots, R_t$ along with a demand for $k_t$ items in each $R_t$, appear online.

Dimensionality Reduction

Learning Powers of Poisson Binomial Distributions

no code implementations18 Jul 2017 Dimitris Fotakis, Vasilis Kontonis, Piotr Krysta, Paul Spirakis

The $k$'th power of this distribution, for $k$ in a range $[m]$, is the distribution of $P_k = \sum_{i=1}^n X_i^{(k)}$, where each Bernoulli random variable $X_i^{(k)}$ has $\mathbb{E}[X_i^{(k)}] = (p_i)^k$.

Optimal Learning of Mallows Block Model

no code implementations3 Jun 2019 Róbert Busa-Fekete, Dimitris Fotakis, Balázs Szörényi, Manolis Zampetakis

The main result of the paper is a tight sample complexity bound for learning Mallows and Generalized Mallows Model.

Efficient Parameter Estimation of Truncated Boolean Product Distributions

no code implementations5 Jul 2020 Dimitris Fotakis, Alkis Kalavasis, Christos Tzamos

A stunning consequence is that virtually any statistical task (e. g., learning in total variation distance, parameter estimation, uniformity or identity testing) that can be performed efficiently for Boolean product distributions, can also be performed from truncated samples, with a small increase in sample complexity.

Aggregating Incomplete and Noisy Rankings

no code implementations2 Nov 2020 Dimitris Fotakis, Alkis Kalavasis, Konstantinos Stavropoulos

We consider the problem of learning the true ordering of a set of alternatives from largely incomplete and noisy rankings.

Solving Inverse Problems for Spectral Energy Distributions with Deep Generative Networks

no code implementations9 Dec 2020 Agapi Rissaki, Orestis Pavlou, Dimitris Fotakis, Vicky Papadopoulou, Andreas Efstathiou

We propose an end-to-end approach for solving inverse problems for a class of complex astronomical signals, namely Spectral Energy Distributions (SEDs).

Efficient Online Learning for Dynamic k-Clustering

no code implementations8 Jun 2021 Dimitris Fotakis, Georgios Piliouras, Stratis Skoulakis

We study dynamic clustering problems from the perspective of online learning.

Clustering

Learning Augmented Online Facility Location

1 code implementation17 Jul 2021 Dimitris Fotakis, Evangelia Gergatsouli, Themis Gouleakis, Nikolas Patris

We prove that the competitive ratio decreases smoothly from sublogarithmic in the number of demands to constant, as the error, i. e., the total distance of the predicted locations to the optimal facility locations, decreases towards zero.

Efficient Algorithms for Learning from Coarse Labels

no code implementations22 Aug 2021 Dimitris Fotakis, Alkis Kalavasis, Vasilis Kontonis, Christos Tzamos

Our main algorithmic result is that essentially any problem learnable from fine grained labels can also be learned efficiently when the coarse data are sufficiently informative.

Label Ranking through Nonparametric Regression

no code implementations4 Nov 2021 Dimitris Fotakis, Alkis Kalavasis, Eleni Psaroudaki

We introduce a generative model for Label Ranking, in noiseless and noisy nonparametric regression settings, and provide sample complexity bounds for learning algorithms in both cases.

regression

Private and Non-private Uniformity Testing for Ranking Data

no code implementations NeurIPS 2021 Róbert Busa-Fekete, Dimitris Fotakis, Emmanouil Zampetakis

We study the problem of uniformity testing for statistical data that consists of rankings over $m$ items where the alternative class is restricted to Mallows models with single parameter.

Identity testing for Mallows model

no code implementations NeurIPS 2021 Róbert Busa-Fekete, Dimitris Fotakis, Balazs Szorenyi, Emmanouil Zampetakis

In this paper, we devise identity tests for ranking data that is generated from Mallows model both in the \emph{asymptotic} and \emph{non-asymptotic} settings.

Differentially Private Regression with Unbounded Covariates

no code implementations19 Feb 2022 Jason Milionis, Alkis Kalavasis, Dimitris Fotakis, Stratis Ioannidis

We provide computationally efficient, differentially private algorithms for the classical regression settings of Least Squares Fitting, Binary Regression and Linear Regression with unbounded covariates.

regression

Perfect Sampling from Pairwise Comparisons

no code implementations23 Nov 2022 Dimitris Fotakis, Alkis Kalavasis, Christos Tzamos

We design a Markov chain whose stationary distribution coincides with $\mathcal{D}$ and give an algorithm to obtain exact samples using the technique of Coupling from the Past.

Fairness in Ranking: Robustness through Randomization without the Protected Attribute

1 code implementation28 Mar 2024 Andrii Kliachkin, Eleni Psaroudaki, Jakub Marecek, Dimitris Fotakis

Second, there are multiple measures of fairness of rankings, and optimization-based methods utilizing a single measure of fairness of rankings may produce rankings that are unfair with respect to other measures.

Attribute Fairness +1

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