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Alexandros G Dimakis

27 accepted papers

2022

Deblurring via Stochastic Refinement

CVPR 2022oral

Image deblurring is an ill-posed problem with multiple plausible solutions for a given input image. However, most existing methods produce a deterministic estimate of the clean image and are trained to minimize pixel-level distortion. These metrics are known to be poorly correlated with human percep…

Cited by 334PDFScholar
2020

Adversarial Video Compression Guided by Soft Edge Detection

ICASSP 2020accepted

We propose a video compression framework using conditional Generative Adversarial Networks (GANs). We rely on two encoders: one that deploys a standard video codec and another one which generates low-level soft edge maps. For decoding, we use a standard video decoder as well as a decoder that is tra…

Cited by 0SourceScholar
2020

Applications of Common Entropy for Causal Inference

NeurIPS 2020poster

We study the problem of discovering the simplest latent variable that can make two observed discrete variables conditionally independent. The minimum entropy required for such a latent is known as common entropy in information theory. We extend this notion to Renyi common entropy by minimizing the R…

Cited by 26SourcePDFScholar
2020

Robust compressed sensing using generative models

NeurIPS 2020poster

We consider estimating a high dimensional signal in $\R^n$ using a sublinear number of linear measurements. In analogy to classical compressed sensing, here we assume a generative model as a prior, that is, we assume the signal is represented by a deep generative model $G: \R^k \rightarrow \R^n$. Cl…

2020

SMYRF - Efficient Attention using Asymmetric Clustering

NeurIPS 2020poster

We propose a novel type of balanced clustering algorithm to approximate attention. Attention complexity is reduced from $O(N^2)$ to $O(N \log N)$, where N is the sequence length. Our algorithm, SMYRF, uses Locality Sensitive Hashing (LSH) in a novel way by defining new Asymmetric transformations and…

2020

Your Local GAN: Designing Two Dimensional Local Attention Mechanisms for Generative Models

CVPR 2020poster

We introduce a new local sparse attention layer that preserves two-dimensional geometry and locality. We show that by just replacing the dense attention layer of SAGAN with our construction, we obtain very significant FID, Inception score and pure visual improvements. FID score is improved from 18.6…

Cited by 84PDFcodeScholar
2019

Inverting Deep Generative models, One layer at a time

NeurIPS 2019poster

We study the problem of inverting a deep generative model with ReLU activations. Inversion corresponds to finding a latent code vector that explains observed measurements as much as possible. In most prior works this is performed by attempting to solve a non-convex optimization problem involving t…

2019

Learning Distributions Generated by One-Layer ReLU Networks

NeurIPS 2019poster

We consider the problem of estimating the parameters of a $d$-dimensional rectified Gaussian distribution from i.i.d. samples. A rectified Gaussian distribution is defined by passing a standard Gaussian distribution through a one-layer ReLU neural network. We give a simple algorithm to estimate the…

2019

Primal-Dual Block Generalized Frank-Wolfe

NeurIPS 2019poster

We propose a generalized variant of Frank-Wolfe algorithm for solving a class of sparse/low-rank optimization problems. Our formulation includes Elastic Net, regularized SVMs and phase retrieval as special cases. The proposed Primal-Dual Block Generalized Frank-Wolfe algorithm reduces the per-iterat…

2019

Provable Certificates for Adversarial Examples: Fitting a Ball in the Union of Polytopes

NeurIPS 2019poster

We propose a novel method for computing exact pointwise robustness of deep neural networks for all convex lp norms. Our algorithm, GeoCert, finds the largest lp ball centered at an input point x0, within which the output class of a given neural network with ReLU nonlinearities remains unchanged.…

2019

Sparse Logistic Regression Learns All Discrete Pairwise Graphical Models

NeurIPS 2019spotlight

We characterize the effectiveness of a classical algorithm for recovering the Markov graph of a general discrete pairwise graphical model from i.i.d. samples. The algorithm is (appropriately regularized) maximum conditional log-likelihood, which involves solving a convex program for each node; for I…

2018

CausalGAN: Learning Causal Implicit Generative Models with Adversarial Training

ICLR 2018poster

We introduce causal implicit generative models (CiGMs): models that allow sampling from not only the true observational but also the true interventional distributions. We show that adversarial training can be used to learn a CiGM, if the generator architecture is structured based on a given causal g…

2018

Experimental Design for Cost-Aware Learning of Causal Graphs

NeurIPS 2018poster

We consider the minimum cost intervention design problem: Given the essential graph of a causal graph and a cost to intervene on a variable, identify the set of interventions with minimum total cost that can learn any causal graph with the given essential graph. We first show that this problem is NP…

Cited by 55SourcePDFScholar
2017

Gradient Coding: Avoiding Stragglers in Distributed Learning

ICML 2017poster

We propose a novel coding theoretic framework for mitigating stragglers in distributed learning. We show how carefully replicating data blocks and coding across gradients can provide tolerance to failures and stragglers for synchronous Gradient Descent. We implement our schemes in python (using MPI)…

Cited by 590SourcePDFScholar
2017

Identifying Best Interventions through Online Importance Sampling

ICML 2017poster

Motivated by applications in computational advertising and systems biology, we consider the problem of identifying the best out of several possible soft interventions at a source node $V$ in an acyclic causal directed graph, to maximize the expected value of a target node $Y$ (located downstream of…

Cited by 94SourcePDFScholar
2017

Model-Powered Conditional Independence Test

NeurIPS 2017poster

We consider the problem of non-parametric Conditional Independence testing (CI testing) for continuous random variables. Given i.i.d samples from the joint distribution $f(x,y,z)$ of continuous random vectors $X,Y$ and $Z,$ we determine whether $X \independent Y \vert Z$. We approach this by convert…

2017

On Approximation Guarantees for Greedy Low Rank Optimization

ICML 2017poster

We provide new approximation guarantees for greedy low rank matrix estimation under standard assumptions of restricted strong convexity and smoothness. Our novel analysis also uncovers previously unknown connections between the low rank estimation and combinatorial optimization, so much so that our…

Cited by 22SourcePDFScholar
2017

Streaming Weak Submodularity: Interpreting Neural Networks on the Fly

NeurIPS 2017oral

In many machine learning applications, it is important to explain the predictions of a black-box classifier. For example, why does a deep neural network assign an image to a particular class? We cast interpretability of black-box classifiers as a combinatorial maximization problem and propose an eff…

2016

Leveraging Sparsity for Efficient Submodular Data Summarization

NeurIPS 2016poster

The facility location problem is widely used for summarizing large datasets and has additional applications in sensor placement, image retrieval, and clustering. One difficulty of this problem is that submodular optimization algorithms require the calculation of pairwise benefits for all items in th…

Cited by 27SourcePDFScholar
2016

Single Pass PCA of Matrix Products

NeurIPS 2016poster

In this paper we present a new algorithm for computing a low rank approximation of the product $A^TB$ by taking only a single pass of the two matrices $A$ and $B$. The straightforward way to do this is to (a) first sketch $A$ and $B$ individually, and then (b) find the top components using PCA on th…

2015

Learning Causal Graphs with Small Interventions

NeurIPS 2015poster

We consider the problem of learning causal networks with interventions, when each intervention is limited in size under Pearl's Structural Equation Model with independent errors (SEM-IE). The objective is to minimize the number of experiments to discover the causal directions of all the edges in a c…

Cited by 124SourcePDFScholar
2015

Orthogonal NMF through Subspace Exploration

NeurIPS 2015poster

Orthogonal Nonnegative Matrix Factorization {(ONMF)} aims to approximate a nonnegative matrix as the product of two $k$-dimensional nonnegative factors, one of which has orthonormal columns. It yields potentially useful data representations as superposition of disjoint parts, while it has been shown…

Cited by 47SourcePDFScholar
2015

Sparse PCA via Bipartite Matchings

NeurIPS 2015poster

We consider the following multi-component sparse PCA problem:given a set of data points, we seek to extract a small number of sparse components with \emph{disjoint} supports that jointly capture the maximum possible variance.Such components can be computed one by one, repeatedly solving the single-c…

Cited by 38SourcePDFScholar