devtools::document()
devtools::check()
We are using three main C functions: fast_dists_by_unit_arma2_par if we are
using openmp (parallel="yes"), fast_dists_and_trans for small n, and
fast_dists_and_trans_by_unit_arma for N>20. (Where 20 is chosen without a lot
of profiling. Basic idea is not to hold large matrices in memory. Matrices are
faster when N is not to large, but bog down when we have large number of
observations.