  Understanding how momentum anisotropies arise in small collision systems is
important for a quantitative understanding of collectivity in terms of QCD
dynamics in small and large collision systems. In this letter we present
results for small collision systems from the newly developed parton cascade
ALPACA, which faithfully encodes the AMY effective kinetic theory. ALPACA
reproduces quantitatively previously know results from a calculation in the
single-hit approximation for small values of the coupling. We discuss in detail
how such a comparison is to be carried out. Particularly at larger coupling a
generic differences between the two approaches becomes apparent, namely that in
parton cascades particles interact over a finite distance while in direct
integrations of the Boltzmann equation the interactions are local. This leads
to quantitative differences in the extracted values for the elliptic flow
coefficient, but also raises questions of a much more fundamental nature that
are worth exploring in the future.
