operating system - why 2D hashmap is memory inefficient? -

i told friends using 2d hashmap discouraged due fragmentation problem? tell if that's case , why?

personally don't see reason discourage use if there legitimate need 2d hashmap.

what may referring how system deals collisions. if 2 different values end same hash value position, do? still need store them both. there few different techniques used handle issue , 1 of them aim start large set of possible hash value positions potentially lead lot of wasted space. better method check next available position until finds free spot.

it has been while since studied storage of these types, seems may talking about. not major issue , not reason never use hashmaps (including 2d ones). i'm not sure on think issues above compound when used in more dimensions (hence more of issue 2d hashmap).