The self-concordant-like property of a smooth convex function is a new analytical structure that generalizes the self-concordant notion. While a wide variety of important applications feature the self-concordant-like property, this concept has heretofore remained unexploited in convex optimization. To this end, we deve…
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Improves statistical learning bounds with self-concordant losses.
We study the smooth structure of convex functions by generalizing a powerful concept so-called self-concordance introduced by Nesterov and Nemirovskii in the early 1990s to a broader class of convex functions, which we call generalized self-concordant functions. This notion allows us to develop a unified framework for …
Unified algorithm for linear bandits with improved regret bound.
Improved Frank-Wolfe algorithm for generalized self-concordant functions converges quickly.
New insights into natural exponential families improve regret bounds for bandit problems.
Interior-point methods adapted for manifolds, achieving similar optimization results.
New bounds on minimax regret for sequential probability assignment using logarithmic loss.
Many problems in statistical learning, imaging, and computer vision involve the optimization of a non-convex objective function with singularities at the boundary of the feasible set. For such challenging instances, we develop a new interior-point technique building on the Hessian-barrier algorithm recently introduced …
We propose a randomized second-order method for optimization known as the Newton Sketch: it is based on performing an approximate Newton step using a randomly projected or sub-sampled Hessian. For self-concordant functions, we prove that the algorithm has super-linear convergence with exponentially high probability, wi…
Unified analysis of online optimization with self-concordant barriers, improving regret bounds.
We propose a variable metric framework for minimizing the sum of a self-concordant function and a possibly non-smooth convex function, endowed with an easily computable proximal operator. We theoretically establish the convergence of our framework without relying on the usual Lipschitz gradient assumption on the smooth…
Many scientific and engineering applications feature nonsmooth convex minimization problems over convex sets. In this paper, we address an important instance of this broad class where we assume that the nonsmooth objective is equipped with a tractable proximity operator and that the convex constraint set affords a self…
Paper improves learning rates for GSC loss functions using iterated Tikhonov regularization.
Improved prediction algorithm for 'easy' sequences with reduced regret.
New method improves HMC for sampling on manifolds.
New sampling method improves accuracy for constrained spaces.
The goal of this note is to construct, on many manifolds, non-trivial concordances from the identity to itself. This produces counterexamples to a recent conjecture by Botvinnik.
We consider the class of convex minimization problems, composed of a self-concordant function, such as the metric, a convex data fidelity term and, a regularizing -- possibly non-smooth -- function . This type of problems have recently attracted a great deal of interest, mainly due to th…
The paper improves confidence set construction for statistical inference.
The classical asymptotic theory for parametric -estimators guarantees that, in the limit of infinite sample size, the excess risk has a chi-square type distribution, even in the misspecified case. We demonstrate how self-concordance of the loss allows to characterize the critical sample size sufficient to guarantee …
We demonstrate how to scalably solve a class of constrained self-concordant minimization problems using linear minimization oracles (LMO) over the constraint set. We prove that the number of LMO calls of our method is nearly the same as that of the Frank-Wolfe method in the L-smooth case. Specifically, our Newton Frank…
Unified CS for GLMs improves bandit regret bounds.
RHMC improves sampling polytopes defined by inequalities with barriers.
We consider distributed convex optimization problems originated from sample average approximation of stochastic optimization, or empirical risk minimization in machine learning. We assume that each machine in the distributed computing system has access to a local empirical loss function, constructed with i.i.d. data sa…
The Riemannian Langevin Algorithm samples from manifolds efficiently.
In this paper we consider the composite self-concordant (CSC) minimization problem, which minimizes the sum of a self-concordant function and a (possibly nonsmooth) proper closed convex function . The CSC minimization is the cornerstone of the path-following interior point methods for solving a broad class of co…
Improved confidence bounds for linear logistic model with applications to bandits.
We compute the effect of concordance surgery, a generalization of knot surgery defined using a self-concordance of a knot, on the Ozsváth-Szabó 4-manifold invariant. The formula involves the graded Lefschetz number of the concordance map on knot Floer homology. The proof uses the sutured Floer TQFT, and a version of su…
New GLB algorithm handles non-stationary data with forgetting.
New algorithm improves sampling from constrained spaces.
This article introduces the concepts around Online Bandit Linear Optimization and explores an efficient setup called SCRiBLe (Self-Concordant Regularization in Bandit Learning) created by Abernethy et. al.\cite{abernethy}. The SCRiBLe setup and algorithm yield a regret bound and polynomial run time comple…
In this paper, we study large-scale convex optimization algorithms based on the Newton method applied to regularized generalized self-concordant losses, which include logistic regression and softmax regression. We first prove that our new simple scheme based on a sequence of problems with decreasing regularization para…
Algorithm for online decision making with unknown dynamics and aggregate feedback.
New approach for online learning with adaptive adversaries, simpler and more effective.
Unified meta-algorithm improves average performance across similar tasks in adversarial bandits.
New algorithm reduces prediction errors across various loss functions.
New algorithm tackles heterogeneous curvature in online convex optimization.
We propose an algorithmic framework for convex minimization problems of a composite function with two terms: a self-concordant function and a possibly nonsmooth regularization term. Our method is a new proximal Newton algorithm that features a local quadratic convergence rate. As a specific instance of our framework, w…
We propose a new proximal, path-following framework for a class of constrained convex problems. We consider settings where the nonlinear---and possibly non-smooth---objective part is endowed with a proximity operator, and the constraint set is equipped with a self-concordant barrier. Our approach relies on the followin…
This work improves regret minimization for logistic bandits by reducing dependence on a large constant.
Given a knot inside an integer homology sphere , the Casson-Lin-Herald invariant can be interpreted as a signed count of conjugacy classes of irreducible representations of the knot complement into which map the meridian of the knot to a fixed conjugacy class. It has the interesting feature that it deter…
A new algorithm reduces communication rounds for distributed convex optimization.
The paper analyzes the excess risk of PCA and provides a precise characterization.
New bounds for online portfolio selection without smoothness assumptions.
In this paper we propose a multi-armed bandit inspired, pool based active learning algorithm for the problem of binary classification. By carefully constructing an analogy between active learning and multi-armed bandits, we utilize ideas such as lower confidence bounds, and self-concordant regularization from the multi…
We consider stochastic second-order methods for minimizing smooth and strongly-convex functions under an interpolation condition satisfied by over-parameterized models. Under this condition, we show that the regularized subsampled Newton method (R-SSN) achieves global linear convergence with an adaptive step-size and a…
We propose a stochastic optimization method for minimizing loss functions, expressed as an expected value, that adaptively controls the batch size used in the computation of gradient approximations and the step size used to move along such directions, eliminating the need for the user to tune the learning rate. The pro…