  The three most common methods, Ewald, fast multipole (FMM) and the
particle-particle particle-mesh (PPPM), used to compute the interactions in
many body Coulombic systems are compared for single and multi-processor
machines. The Ewald method is recommended for systems of a few hundred
particles per processor or less. For larger systems the PPPM method is
suggested. The FMM is slower and more difficult to code efficiently.
