A Note on Bounding Regret of the C$^2$UCB Contextual Combinatorial Bandit
This is an incremental correction for researchers in bandit algorithms, ensuring theoretical reliability of prior results.
The paper identifies an error in the proof of bounded regret for the C²UCB contextual combinatorial bandit algorithm and provides a corrected proof to maintain the original regret bound.
We revisit the proof by Qin et al. (2014) of bounded regret of the C$^2$UCB contextual combinatorial bandit. We demonstrate an error in the proof of volumetric expansion of the moment matrix, used in upper bounding a function of context vector norms. We prove a relaxed inequality that yields the originally-stated regret bound.