Changes

Distortion is [[Hans Kmoch|Kmoch's]] term for horizontal splitting of pawns caused by advances. One may use something like this based on [[Pawn Fills|rearfill]], xor and [[Population Count|population count]] to get an idea of distortion. It considers the rank-difference of two file-adjacent pawns (if any) as distortion penalty - the higher the worse. [[Isolated Pawns (Bitboards)#IsolanisSetWise|Half-isolated]] or even [[Isolated Pawn|isolated pawns]] contribute a distortion penalty according to the size of their rearfill from 2 to 7 for each empty neighboring file, which discourages advancement of such pawns, interacting with terms considerring (half-) isolated pawns. Alternatively, for a "reverse" distortion penalty to encourage advancement of half-isolanis, one may use [[Pawn Fills|frontfill]] instead with a slightly different semantic is case of [[Doubled Pawn|doubled pawns]].