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We formulate approximate Bayesian inference in non-conjugate temporal and spatio-temporal Gaussian process models as a simple parameter update rule applied during Kalman smoothing. This viewpoint encompasses most inference schemes,…

Machine Learning · Statistics 2020-07-14 William J. Wilkinson , Paul E. Chang , Michael Riis Andersen , Arno Solin

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…

Optimization and Control · Mathematics 2016-05-24 Sashank J. Reddi , Suvrit Sra , Barnabas Poczos , Alex Smola

Classical convergence analyses for optimization algorithms rely on the widely-adopted uniform smoothness assumption. However, recent experimental studies have demonstrated that many machine learning problems exhibit non-uniform smoothness,…

Machine Learning · Computer Science 2024-09-27 Zhenyu Sun , Ermin Wei

We study the optimization of non-convex functions that are not necessarily smooth (gradient and/or Hessian are Lipschitz) using first order methods. Smoothness is a restrictive assumption in machine learning in both theory and practice,…

Optimization and Control · Mathematics 2025-06-27 Daniel Yiming Cao , August Y. Chen , Karthik Sridharan , Benjamin Tang

Generalized and Simulated Method of Moments are often used to estimate structural Economic models. Yet, it is commonly reported that optimization is challenging because the corresponding objective function is non-convex. For smooth…

Econometrics · Economics 2025-07-11 Jean-Jacques Forneron , Liang Zhong

A practical challenge for structural estimation is the requirement to accurately minimize a sample objective function which is often non-smooth, non-convex, or both. This paper proposes a simple algorithm designed to find accurate solutions…

Econometrics · Economics 2025-08-19 Jean-Jacques Forneron

Coping with outliers contaminating dynamical processes is of major importance in various applications because mismatches from nominal models are not uncommon in practice. In this context, the present paper develops novel fixed-lag and…

Systems and Control · Computer Science 2018-11-29 Shahrokh Farahmand , Georgios B. Giannakis , Daniele Angelosante

Using a perturbation technique, we derive a new approximate filtering and smoothing methodology generalizing along different directions several existing approaches to robust filtering based on the score and the Hessian matrix of the…

Methodology · Statistics 2023-06-06 Giuseppe Buccheri , Giacomo Bormetti , Fulvio Corsi , Fabrizio Lillo

In this manuscript the fixed-lag smoothing problem for conditionally linear Gaussian state-space models is investigated from a factor graph perspective. More specifically, after formulating Bayesian smoothing for an arbitrary state-space…

Computation · Statistics 2017-05-23 Giorgio M. Vitetta , Emilio Sirignano , Francesco Montorsi

Estimating the state of a dynamical system from a series of noise-corrupted observations is fundamental in many areas of science and engineering. The most well-known method, the Kalman smoother (and the related Kalman filter), relies on…

Machine Learning · Statistics 2017-04-24 Luca Ambrogioni , Umut Güçlü , Eric Maris , Marcel van Gerven

Smoothing is essential to many oceanographic, meteorological and hydrological applications. The interval smoothing problem updates all desired states within a time interval using all available observations. The fixed-lag smoothing problem…

Chaotic Dynamics · Physics 2015-06-26 S. Ravela , D. McLaughlin

This paper presents a robust fixed lag smoother for a class of nonlinear uncertain systems. A unified scheme, which combines a nonlinear robust estimator with a stable fixed lag smoother, is presented to improve the error covariance of the…

Systems and Control · Computer Science 2013-09-10 Obaid Ur Rehman , Ian R. Petersen

We propose a primal-dual smoothing framework for finding a near-stationary point of a class of non-smooth non-convex optimization problems with max-structure. We analyze the primal and dual gradient complexities of the framework via two…

Optimization and Control · Mathematics 2023-07-19 Renbo Zhao

With the ever increasing computational power available and the development of high-performances computing, investigating the properties of realistic very large-scale nonlinear dynamical systems has been become reachable. It must be noted…

This paper considers the fixed point problem for a nonexpansive mapping on a real Hilbert space and proposes novel line search fixed point algorithms to accelerate the search. The termination conditions for the line search are based on the…

Optimization and Control · Mathematics 2015-09-21 Hideaki Iiduka

We consider approximate maximum likelihood parameter estimation in nonlinear state-space models. We discuss both direct optimization of the likelihood and expectation--maximization (EM). For EM, we also give closed-form expressions for the…

Methodology · Statistics 2015-11-03 Juho Kokkala , Arno Solin , Simo Särkkä

In the lines of our approach in \cite{Ouorou2019}, where we exploit Nesterov fast gradient concept \cite{Nesterov1983} to the Moreau-Yosida regularization of a convex function, we devise new proximal algorithms for nonsmooth convex…

Optimization and Control · Mathematics 2020-10-08 Adam Ouorou

We propose a scalable robust learning algorithm combining kernel smoothing and robust optimization. Our method is motivated by the convex analysis perspective of distributionally robust optimization based on probability metrics, such as the…

Machine Learning · Computer Science 2022-02-22 Jia-Jie Zhu , Christina Kouridi , Yassine Nemmour , Bernhard Schölkopf

The Bayesian smoothing equations are generally intractable for systems described by nonlinear stochastic differential equations and discrete-time measurements. Gaussian approximations are a computationally efficient way to approximate the…

Dynamical Systems · Mathematics 2016-04-05 Juha Ala-Luhtala , Simo Särkkä , Robert Piché

Continuous phase estimation is known to be superior in accuracy as compared to static estimation. The estimation process is, however, desired to be made robust to uncertainties in the underlying parameters. Here, homodyne phase estimation…

Optimization and Control · Mathematics 2015-09-14 Shibdas Roy , Obaid Ur Rehman , Ian R. Petersen , Elanor H. Huntington