  The paper presents a numerical implementation of the gravitational N-body
problem with contact interactions between non-spherically shaped bodies. The
work builds up on a previous implementation of the code and extends its
capabilities. The number of bodies handled is significantly increased through
the use of a CUDA/GPU-parallel octree structure. The implementation of the code
is discussed and its performance are compared against direct N$^2$ integration.
The code features both smooth (force-based) and non-smooth (impulse-based)
methods, as well as a visco-elastic non-smooth method, to handle contact
interaction between bodies. The numerical problem of simulating "rubble-pile"
asteroid gravitational aggregation processes is addressed. We discuss the
features of the problem and derive criteria to set up the numerical simulation
from the dynamical constraints of the combined gravitational-collisional
problem. Examples of asteroid aggregation scenarios that could benefit from
such implementation are finally presented.
