Each of the Following 3 Programs Computes the Matrices gxx and hxx: Use the one that suits your needs best
gxx_hxx.m
gxx_hxx_sparse.m (Recommended for use when gxx_hxx.m runs into memory problems. Slower than gxx_hxx.m)
gxx_hxx_noloop.m (Faster than gxx_hxx.m, but more prone to memory problems)