A conjugate Rosen’s gradient projection method with global line search for piecewise linear optimization∗

The Kelley cutting plane method is one of the methods commonly used to optimize the dual function in the Lagrangian relaxation scheme. Usually the Kelley cutting plane method uses the simplex method as the optimization engine. It is well known that the simplex method leaves the current vertex, follows an ascending edge and stops at the nearest vertex. What would happen if one would continue the line search up to the best point instead? As a possible answer, we propose the face simplex method, which freely explores the polyhedral surface by following the Rosen’s gradient projection combined with a global line search on the whole surface. Furthermore, to avoid the zig-zagging of the gradient projection, we propose a conjugate gradient version of the face simplex method. We have implemented this method in Matlab. This implementation clearly outperforms basic Matlab implementations of the simplex method. In the case of state-of-the-art simplex implementations in C, our Matlab implementation is only competitive for the case of many cutting planes.