This implementation and associated paper improve the cache locality to make the algorithm more competitive https://github.com/dmalhotra/pvfmm https://github.com

This implementation and associated paper improve the cache locality to make the algorithm more competitive https://github.com/dmalhotra/pvfmm https://github.com/dmalhotra/pvfmm They compare solving toy problems with different methods here https://arxiv.org/pdf/1408.6497.pdf https://arxiv.org/pdf/1408.6497.pdf But as you mention, this is just fiddling with constants, and it still may be too costly for your problem