2023-04-11-baby23a.md

title	abstract	section	layout	series	publisher	issn	id	month	tex_title	firstpage	lastpage	page	order	cycles	bibtex_author	author	date	address	container-title	volume	genre	issued	pdf	extras
Second Order Path Variationals in Non-Stationary Online Learning	We consider the problem of universal dynamic regret minimization under exp-concave and smooth losses. We show that appropriately designed Strongly Adaptive algorithms achieve a dynamic regret of $\tilde O(d^2 n^{1/5} [\mathcal{TV}_1(w_{1:n})]^{2/5} \vee d^2)$, where $n$ is the time horizon and $\mathcal{TV}_1(w_{1:n})$ a path variational based on second order differences of the comparator sequence. Such a path variational naturally encodes comparator sequences that are piece-wise linear – a powerful family that tracks a variety of non-stationarity patterns in practice (Kim et al., 2009). The aforementioned dynamic regret is shown to be optimal modulo dimension dependencies and poly-logarithmic factors of $n$. To the best of our knowledge, this path variational has not been studied in the non-stochastic online learning literature before. Our proof techniques rely on analysing the KKT conditions of the offline oracle and requires several non-trivial generalizations of the ideas in Baby and Wang (2021) where the latter work only implies an $\tilde{O}(n^{1/3})$ regret for the current problem.	Regular Papers	inproceedings	Proceedings of Machine Learning Research	PMLR	2640-3498	baby23a	0	Second Order Path Variationals in Non-Stationary Online Learning	9024	9075	9024-9075	9024	false	Baby, Dheeraj and Wang, Yu-Xiang	given family Dheeraj Baby given family Yu-Xiang Wang	2023-04-11		Proceedings of The 26th International Conference on Artificial Intelligence and Statistics	206	inproceedings	date-parts 2023 4 11	https://proceedings.mlr.press/v206/baby23a/baby23a.pdf