1. A computer-implemented method for assigning a plurality of resource requests among a plurality of resource providers, said plurality of resource requests including a plurality of pending resource requests assigned among said resource providers according to an existing assignment set, wherein said existing assignment set defines a root node of a search tree, said method comprising the steps of: (a) expanding said root node by forming one or more next-level nodes, each of said next-level nodes corresponding to said root node but being further defined by a reassignment of one of said pending resource requests between one of said resource providers and another of said resource providers; (b) estimating, for each of said next-level nodes, a stress value representing a degree of undesirability of the respective reassignment; and (c) generating a new assignment set corresponding to one of said next-level nodes having a minimum stress value.