  We test the performances of two different approaches to the computation of
forces for molecular dynamics simulations on Graphics Processing Units. A
"vertex-based" approach, where a computing thread is started per particle, is
compared to a newly proposed "edge-based" approach, where a thread is started
per each potentially non-zero interaction. We find that the former is more
efficient for systems with many simple interactions per particle, while the
latter is more efficient if the system has more complicated interactions or
fewer of them. By comparing computation times on more and less recent GPU
technology, we predict that, if the current trend of increasing the number of
processing cores - as opposed to their computing power - remains, the
"edge-based" approach will gradually become the most efficient choice in an
increasing number of cases.
