We denote by D t the distribution over The direction e t selected at the tth round is the one minimizing the directional derivative, that is where t is the average error of h t given by The remaining steps of our algorithm can be determined as in the case of AdaBoost.
given the direction e t , the best step α t is obtained by solving the equation dF (α t−1 +αtet) dαt = 0, which admits the closed-form solution α t = 1 2 log 1− t t .