@Article{ frank.ea:theoretical:2001, abstract = {We examine search algorithms for games with imperfect information.We first investigate Monte Carlo sampling, showing that for verysimple game trees the chance of finding an optimal strategy rapidlyapproaches zero as size of the tree increases. We identify thereasons for this sub-optimality, and show that the same problemsoccur in Bridge, a popular real-world imperfect information game.We then analyse the complexity of the underlying problem, proving itto be NP-complete and describing several polynomial time heuristics.We evaluate these heuristics theoretically and experimentally,demonstrating that they significantly out-perform Monte Carlosampling. Indeed, on a set of Bridge problems drawn from adefinitive expert text, our heuristics consistently identifystrategies as good as, or superior to, the expert solutions - thefirst time a game-general tree search algorithm has been capable ofsuch performance.}, author = {Ian Frank and David Basin}, journal = {Theoretical Computer Science}, month = {February}, language = {USenglish}, number = {1-2}, pages = {217--256}, ps = {papers/2001/tcs-search.ps.gz}, title = {A Theoretical and Empirical Investigation of Search in Imperfect Information Games}, volume = 252, year = 2001 }