profiling ublas code

Hi, I am trying to optimize my ublas-containing code. The profile from gprof showed these two functions as the top 2 time-consuming ones. Could somebody explain to me a little bit about what these mean? % cumulative self self total time seconds seconds calls ms/call ms/call name 23.76 93.11 93.11 137604968 0.00 0.00 vector * __uninitialized_copy_aux *, vector *>(vector *, vector *, vector *, __false_type) 21.49 177.31 84.20 41208000 0.00 0.00 vector::operator=(vector const &) Thanks, Julian