“…The minimization of a nonlinear function subject to bounds on the variables has been the subject of intense previous work, along many possible avenues. Major classes of algorithms for bound-constrained problems include the ones based on: active or -active set methods (see, e.g., [1,13,32] and more recently [18] for a short review on active set methods); trust-region methods (see, e.g., [6,7,14,22,24]); interior-point methods (see, e.g., [5,10,19]); line-search projected gradient methods (see, e.g., [2] and the references therein; see also [3,25,35] for a limited memory BFGS method); and filter type methods (see [31]). The approach proposed and analyzed in this paper belongs to the trust-region class but also shares the flavor of projected gradient methods.…”