NK model
The NK model is a mathematical model described by its primary inventor Stuart Kauffman as a "tunably rugged" fitness landscape. "Tunable ruggedness" captures the intuition that both the overall size of the landscape and the number of its local "hills and valleys" can be adjusted via changes to its two parameters, N {\displaystyle N} and K {\displaystyle K} , with N {\displaystyle N} being the length of a string of evolution and K {\displaystyle K} determining the level of landscape ruggedness.