quadtree

References:
[1] http://www.lcad.icmc.usp.br/~jbatista/procimg/quadtree_neighbours.pdf
[2] http://homepage.divms.uiowa.edu/~kvaradar/sp2012/daa/ann.pdf
[3] http://web.archive.org/web/20120907211934/http://ww1.ucmss.com/books/LFS/CSREA2006/MSV4517.pdf
[3] operations cost https://arxiv.org/pdf/1712.05591.pdf
Resources:

[1] quadtree neighbors https://bl.ocks.org/mbostock/4343214
[2] neighbors https://gist.github.com/patricksurry/6478178
[3] neighbors https://github.com/geidav/quadtree-neighbor-finding/blob/master/neighbors.py
[4] https://geidav.wordpress.com/2017/12/02/advanced-octrees-4-finding-neighbor-nodes/
[5] for check https://github.com/xoolive/quadtree

[6] gaussian kd-tree https://www.cg.tuwien.ac.at/courses/Visualisierung2/HallOfFame/2012/7-Labschuetz/Homepage/index.html#References
[7] quadtree over CUDA source code http://ecee.colorado.edu/~siewerts/extra/code/example_code_archive/a490dmis_code/CUDA/cuda_work/samples/Samples.html