I read the full paper after posting my initial comment. Not really - BH does use a “opening angle” parameter, but for FMM you use an order of expansion which pr

I read the full paper after posting my initial comment. Not really - BH does use a “opening angle” parameter, but for FMM you use an order of expansion which provides a strict error bound in terms of accuracy which was derived in Greengard and Rohklin’s original paper on but have been expanded to other potentials. To me it’s just a minor (but nonetheless interesting) variation of an existing method; there have been many of these. They don’t compare it to other tree based methods in performance in the paper which says to me that is merits aren’t really that clear… with long range potentials FP inaccuracies mean none of this is exact anyway.