1. A program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine to perform method steps for determining a gain value of a feature in an MEMD (maximum entropy/minimum divergence) probability model, the method comprising the steps of: receiving as input, a corpus comprising a plurality of words, a list of features representing one of grammatical and semantic relationships among words, and a set of evaluation points; for each feature; determining a value of a gainsum derivative function at each of said evaluation points, resulting in a gainsum derivative vector; selecting a continuous approximation function based upon said gainsum derivative vector; determining the argument value that maximizes the value of an approximated gain function from said approximation function; and determining the approximate gain value by evaluating the approximated gain function at said argument value; and outputting for use in constructing an MEMD model one of (1) the features and corresponding argument values, for those features having an approximate gain value that exceeds a predetermined threshold value and (2) all the features and corresponding approximate gain values and argument values.