In this work we consider the stochastic minimization of nonsmooth convex loss functions, a central problem in machine learning. We propose a novel algorithm called Accelerated Nonsmooth Stochastic Gradient Descent (ANSGD), which exploits the structure of common nonsmooth loss functions to achieve optimal convergence ra…
arXiv research
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Many machine learning techniques sacrifice convenient computational structures to gain estimation robustness and modeling flexibility. However, by exploring the modeling structures, we find these "sacrifices" do not always require more computational efforts. To shed light on such a "free-lunch" phenomenon, we study the…
New stability bounds for SGD on nonsmooth convex losses.
Develops a fast algorithm for high-dimensional LASSO penalized quantile regression.
Paper tackles efficient SVM classification over decentralized networks.
New solver for MKL-SVM with 0/1 loss function.
A new R package for high-dimensional regression and precision matrix estimation.
Paper introduces privacy-preserving inventory policy learning for feature-based newsvendor with unknown demand.
New theory for nonsmooth systems helps optimize and control complex functions.
We study the performance of a family of randomized parallel coordinate descent methods for minimizing the sum of a nonsmooth and separable convex functions. The problem class includes as a special case L1-regularized L1 regression and the minimization of the exponential loss ("AdaBoost problem"). We assume the input da…
Nesterov's extrapolation improves convergence in nonsmooth optimization.
In regularized risk minimization, the associated optimization problem becomes particularly difficult when both the loss and regularizer are nonsmooth. Existing approaches either have slow or unclear convergence properties, are restricted to limited problem subclasses, or require careful setting of a smoothing parameter…
We introduce a class of quadratic support (QS) functions, many of which play a crucial role in a variety of applications, including machine learning, robust statistical inference, sparsity promotion, and Kalman smoothing. Well known examples include the l2, Huber, l1 and Vapnik losses. We build on a dual representation…
PPGD solves nonconvex nonsmooth optimization problems without KL property.
Paper introduces MKL--SVM for SVM with loss.
Study compares nonsmooth spaces with integrable Ricci bounds.
We analyze stochastic algorithms for optimizing nonconvex, nonsmooth finite-sum problems, where the nonconvex part is smooth and the nonsmooth part is convex. Surprisingly, unlike the smooth case, our knowledge of this fundamental problem is very limited. For example, it is not known whether the proximal stochastic gra…
Regularity results for geodesic X-ray transform on nonsmooth manifolds
Paper develops algorithms for nonsmooth, nonconvex statistical learning problems.
New Langevin Monte Carlo algorithms for sampling from nonsmooth distributions.
We consider a class of nonconvex nonsmooth optimization problems whose objective is the sum of a smooth function and a finite number of nonnegative proper closed possibly nonsmooth functions (whose proximal mappings are easy to compute), some of which are further composed with linear maps. This kind of problems arises …
New methods help escape strict saddle points in nonsmooth optimization.
We present a stochastic setting for optimization problems with nonsmooth convex separable objective functions over linear equality constraints. To solve such problems, we propose a stochastic Alternating Direction Method of Multipliers (ADMM) algorithm. Our algorithm applies to a more general class of nonsmooth convex …
This paper is concerned with the factorization form of the rank regularized loss minimization problem. To cater for the scenario in which only a coarse estimation is available for the rank of the true matrix, an -norm regularized term is added to the factored loss function to reduce the rank adaptively; and…
The paper guarantees global stability for stochastic subgradient methods in nonsmooth nonconvex optimization.
We extend the well-known BFGS quasi-Newton method and its memory-limited variant LBFGS to the optimization of nonsmooth convex objectives. This is done in a rigorous fashion by generalizing three components of BFGS to subdifferentials: the local quadratic model, the identification of a descent direction, and the Wolfe …
Paper develops privacy-preserving federated learning for nonsmooth objectives.
Sign-RIP improves robust low-rank matrix recovery by preserving norms even with corrupted measurements.
Improved shuffling gradient methods converge faster for nonsmooth convex optimization.
We study the phase retrieval problem, which solves quadratic system of equations, i.e., recovers a vector from its magnitude measurements . We develop a gradient-like algorithm (referred to as RWF representing reshaped W…
Develops a mathematical model for automatic differentiation in machine learning.
With the large rising of complex data, the nonconvex models such as nonconvex loss function and nonconvex regularizer are widely used in machine learning and pattern recognition. In this paper, we propose a class of mini-batch stochastic ADMMs (alternating direction method of multipliers) for solving large-scale noncon…
Two new methods solve nonsmooth optimization on Riemannian Stiefel manifold.
We consider in this paper a class of composite optimization problems whose objective function is given by the summation of a general smooth and nonsmooth component, together with a relatively simple nonsmooth term. We present a new class of first-order methods, namely the gradient sliding algorithms, which can skip the…
In this paper, we consider the problem of minimizing the average of a large number of nonsmooth and convex functions. Such problems often arise in typical machine learning problems as empirical risk minimization, but are computationally very challenging. We develop and analyze a new algorithm that achieves robust linea…
New method solves nonsmooth low-rank matrix optimization problems efficiently.
New algorithm for fast nonsmooth optimization with applications in image processing and machine learning.
Frank-Wolfe methods (FW) have gained significant interest in the machine learning community due to its ability to efficiently solve large problems that admit a sparse structure (e.g. sparse vectors and low-rank matrices). However the performance of the existing FW method hinges on the quality of the linear approximatio…
Study on numerical reliability of AD for MaxPool in neural nets.
We introduce a proximal subdifferential and develop a calculus for nonsmooth functions defined on any Riemannian manifold . We give several applications of this theory, concerning: 1) differentiability and geometrical properties of the distance function to a closed subset of ; 2) solvability and implicit func…
Improved DP optimization for nonconvex, nonsmooth objectives with reduced sample complexity.
We consider the problem of minimizing a difference-of-convex (DC) function, which can be written as the sum of a smooth convex function with Lipschitz gradient, a proper closed convex function and a continuous possibly nonsmooth concave function. We refine the convergence analysis in [38] for the proximal DC algorithm …
The use of convex regularizers allows for easy optimization, though they often produce biased estimation and inferior prediction performance. Recently, nonconvex regularizers have attracted a lot of attention and outperformed convex ones. However, the resultant optimization problem is much harder. In this paper, for a …
This paper concerns dictionary learning, i.e., sparse coding, a fundamental representation learning problem. We show that a subgradient descent algorithm, with random initialization, can provably recover orthogonal dictionaries on a natural nonsmooth, nonconvex minimization formulation of the problem, under mi…
We study the dual formulation of the utility maximization problem in incomplete markets when the utility function is finitely valued on the whole real line. We extend the existing results in this literature in two directions. First, we allow for nonsmooth utility functions, so as to include the shortfall minimization p…
Unified Lagrangian-based methods for nonsmooth nonconvex optimization.
Nonconvex and nonsmooth problems have recently attracted considerable attention in machine learning. However, developing efficient methods for the nonconvex and nonsmooth optimization problems with certain performance guarantee remains a challenge. Proximal coordinate descent (PCD) has been widely used for solving opti…
Study on Adam-family methods for nonsmooth optimization with convergence guarantees.