An accurate active set conjugate gradient algorithm with project search for bound constrained optimization

In the paper, we propose an active set identification technique which accurately identifies active constraints in a neighborhood of an isolated stationary point without strict complementarity conditions. Based on the identification technique, we propose a conjugate gradient algorithm for large-scale bound constrained optimization. In the algorithm, the recently developed modified Polak-Ribiére-Polyak method is used to update the variables with indices outside of the active set, while the projected gradient method is used to update the active variables. Under appropriate conditions, we show that the proposed method is globally convergent. Numerical experiments are presented using bound constrained problems in the CUTEr test problem library.