Cache algorithm
Least Recently Used (LRU): deletes the least recently used items first. This algorithm requires keeping track of what was used when. This is expensive if one wants to make sure the algorithm always discards the least recently used item. General implementations of this technique require to keep "age bits" for cache-lines and track the "Least Recently Used" cache-line based on age-bits. In such implementation, every time a cache-line is used, the age of all other cache-lines changes. LRU is actually a family of caching algorithms with members including: 2Q by Theodore Johnson and Dennis Shasha and LRU/K by Pat O'Neil, Betty O'Neil and Gerhard Weikum.