Reducing the number of redundant pair-wise interactions in hydrodynamic
  meshless methods
  Widely used Lagrangian numerical codes that compute the physical interaction
with neighbouring resolution elements (particles), duplicate the calculation of
the interaction between pairs of particles. We developed an algorithm that
reduces the number of redundant calculations. The algorithm makes use of a hash
function to flag already computed interactions and eventual collisions. The
result of the hashing is stored in two caches. Without limiting the cache
memory usage, all duplicated calculations can be avoided, achieving the
speed-up of a factor on two. We show that, limiting the cache size (in bits) to
double the typical number of neighbouring particles, 70 per cent of the
redundant calculations can be avoided, yielding a speed-up of almost 35 per
cent.
