作者: Qun Xie , A.R. Barron
DOI: 10.1109/18.825803
关键词:
摘要: For problems of data compression, gambling, and prediction individual sequences x/sub 1/, /spl middot//spl middot/, n/ the following questions arise. Given a target family probability mass functions p(x/sub n/|/spl theta/), how do we choose function q(x/sub n/) so that it approximately minimizes maximum regret/belowdisplayskip10ptminus6pt max (log1/q(x/sub n/)-log1/p(x/sub theta//spl circ/)) achieves best constant C in asymptotics minimax regret, which is form (d/2)log(n/2/spl pi/)+C+o(1), where d parameter dimension? Are there easily implementable strategies q achieve those asymptotics? And does solution to worst case sequence problem relate corresponding expectation version min/sub q/ max/sub 0/ E/sub 0/(log1/q(x/sub theta/))? In discrete memoryless case, with given alphabet size m, Bayes procedure Dirichlet(1/2, 1/2) prior asymptotically maximin. Simple modifications are shown be minimax. The C/sub m/=log(/spl Gamma/(1/2)/sup m//(/spl Gamma/(m/2)) agrees logarithm integral square root determinant Fisher information. Moreover, our optimal for also version. Analogous conclusions prediction, compression when, each observation, one has access side information from an k. this setting regret k(m-1)/2logn/2/spl pi/k+kC/sub m/+o(1).