Comment on "N-body simulations of gravitational dynamics" by Dehnen and
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  It is shown that the historical summary of the growth in size of N-body
simulations as measured by particle number in this review is missing some key
milestones. Size matters, because particle number with appropriate force
smoothing is a key method to suppress unwanted discreteness, so that the
initial conditions and equations of motion are appropriate to growth by
gravitational instability in a Poisson-Vlasov system appropriate to a Universe
with dark matter. Published strong constraints on what can be done are not
included in the review.
