  The goal of this paper is to characterize Gaussian-Process optimization in
the setting where the function domain is large relative to the number of
admissible function evaluations, i.e., where it is impossible to find the
global optimum. We provide upper bounds on the suboptimality (Bayesian simple
regret) of the solution found by optimization strategies that are closely
related to the widely used expected improvement (EI) and upper confidence bound
(UCB) algorithms. These regret bounds illuminate the relationship between the
number of evaluations, the domain size (i.e. cardinality of finite domains /
Lipschitz constant of the covariance function in continuous domains), and the
optimality of the retrieved function value. In particular, they show that even
when the number of evaluations is far too small to find the global optimum, we
can find nontrivial function values (e.g. values that achieve a certain ratio
with the optimal value).
