1. A method of improving classifier performance, comprising: inputting threshold vectors T k =(t 1k , t 2k ,. .. , t nk ) into a classifier comprising a cascade of n classification stages, each classification stage i having a respective classification boundary controlled by a respective threshold t ik , wherein i=1,. .. , n, n has an integer value greater than 1, k is an integer, and each threshold vector T k corresponds to a respective operating point of the classifier; and identifying threshold vectors corresponding to respective points on a receiver operating characteristic (ROC) curve approximating a target discrimination performance for multiple operating points of the classifier.