We study the prophet inequality, a fundamental problem in online decision-making and optimal stopping, in a practical setting where rewards are observed only through noisy realizations and reward distributions are unknown. At each stage, the decision-maker receives a noisy reward whose true value follows a linear model with an unknown latent parameter, and observes a feature vector drawn from a distribution. To address this challenge, we propose algorithms that integrate learning and decision-making via lower-confidence-bound (LCB) thresholding. In the i.i.d.\ setting, we establish that both an Explore-then-Decide strategy and an $\varepsilon$-Greedy variant achieve the sharp competitive ratio of $1 - 1/e$, under a mild condition on the optimal value. For non-identical distributions, we show that a competitive ratio of $1/2$ can be guaranteed against a relaxed benchmark. Moreover, with limited window access to past rewards, the tight ratio of $1/2$ against the optimal benchmark is achieved.

Bayesian methods lie at the heart of modern data science and provide a powerful scaffolding for estimation in data-constrained settings and principled quantification and propagation of uncertainty. Yet in many real-world use cases where these methods are deployed, there is a natural need to preserve the privacy of the individuals whose data is being scrutinized. While a number of works have attempted to approach the problem of differentially private Bayesian estimation through either reasoning about the inherent privacy of the posterior distribution or privatizing off-the-shelf Bayesian methods, these works generally do not come with rigorous utility guarantees beyond low-dimensional settings. In fact, even for the prototypical tasks of Gaussian mean estimation and linear regression, it was unknown how close one could get to the Bayes-optimal error with a private algorithm, even in the simplest case where the unknown parameter comes from a Gaussian prior. In this work, we give the first efficient algorithms for both of these problems that achieve mean-squared error $(1+o(1))\mathrm{OPT}$ and additionally show that both tasks exhibit an intriguing computational-statistical gap. For Bayesian mean estimation, we prove that the excess risk achieved by our method is optimal among all efficient algorithms within the low-degree framework, yet is provably worse than what is achievable by an exponential-time algorithm. For linear regression, we prove a qualitatively similar lower bound. Our algorithms draw upon the privacy-to-robustness framework of arXiv:2212.05015, but with the curious twist that to achieve private Bayes-optimal estimation, we need to design sum-of-squares-based robust estimators for inherently non-robust objects like the empirical mean and OLS estimator. Along the way we also add to the sum-of-squares toolkit a new kind of constraint based on short-flat decompositions.

Risdefined X Rd and is randomvectorP .

However, their data structure requires a significantly increased super-linear storage space, as well as super-linear preprocessing time. These limitations inhibit the practical applicability of their approach on large datasets.

The algorithm [62] consider Algorithm 2 for the stochastic generalized linear bandit problem. Assume thatθ is the true parameter of the reward model. Then we consider the lower bounds. For fj(A) = 12(ej1eTj2 +ej2eTj1),A with j1 j2, fj(Ai) is only 1 wheni = j and 0 otherwise. With Claim D.12 and Claim D.11 we get that g C q To get 1), we writeVl = [v1, vl] Rd l and V l = [vl+1, vk].

In the deterministic setting where the data is deterministically given without any probabilistic assumptions, significant advances inDP linear regression has been made [77,57,68, 16, 7, 83, 31, 67, 82, 71]. In the randomized settings where each example{xi,yi} is drawn i.i.d. We explain the closely related ones in Section 2.3, with analysis when the covariance matrixhasaspectralgap. The resulting utility guarantees are the same as those from [23], which are discussedinSection2.3. When privacy is not required, we know from Theorem 2.2 that under Assumptions A.1-A.3, we can achieve an error rate of O(κ p V/n).

After prediction, the true labelyt is revealed and the lossℓ(yt,ˆyt)is incurred.

Wefocusonsixmethods:(i)discriminative K-means (DisKmeans) in Ye et al. (2008); (ii) a discriminative clustering formulation described inBach andHarchaoui (2008); Flammarion etal.(2017); We compare two classesF of feature mappings: linear functions and fully-connected neural networks with one hidden layer that has 100 nodes. An epoch refers ton/B = 12 consecutive iterations. The learning curves in Figure 1 shows the advantage of neural network and demonstrates the flexibility of CURE with nonlinear function classes. One of the main obstacles is the complicated piecewise definition off, which prevent us from obtaining closed form formulae.

This is the appendix for "A general approximation lower bound inLp norm, with applications to feed-forwardneuralnetworks". Layer L consists of a single node: the output neuron. Note that skip connections are allowed, i.e., there can be connections between non-consecutivelayers. We now explain how to derive Proposition 1 (with an arbitrary range[a,b]) as a straightforward consequenceofProposition7. Proof(ofProposition1). In order to apply Proposition 7, we reduce the problem from[a,b] to [0,1] by translating and rescaling every function inG.

Whilepreviousworkprovide worst-case bounds for arbitrary convex functions, it is often the case that the function at hand belongs to a smaller class that enjoys faster rates.