  A cutting-edge software is presented to tackle the Newton-Euler equations
governing the dynamics of granular flows and dense suspensions in Newtonian
fluids. In particular, we propose an implementation of a fixed-radius near
neighbours search based on an efficient counting sort algorithm with an
improved symmetric search. The adopted search method drastically reduces the
computational cost and allows an efficient parallelisation even on a single
node through the multi-threading paradigm. Emphasis is also given to the memory
efficiency of the code since the history of the contacts among particles has to
be traced to model the frictional contributions, when dealing with granular
flows of rheological interest that consider non-smooth interacting particles.
An effective procedure based on an estimate of the maximum number of the
smallest particles surrounding the largest one (given the radii distribution)
and a sort applied only to the surrounding particles only is implemented,
allowing us to effectively tackle the rheology of non-monodispersed particles
with high size-ratio in large domains. Finally, we present validations and
verification of the numerical procedure, by comparing with previous simulations
and experiments, and present new software capabilities.
