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 and K, defined below. The NK model has found application in a wide variety of fields, most notably the theoretical study of evolutionary biology, immunology,optimisation and complex systems.

An early version of the model, which considered only the smoothest (K = 0) and most rugged (K = N) landscapes, was presented in Kauffman and Levin (1987)^[1]. The model as it is currently known first appeared in Kauffman and Weinberger (1989)^[2].

One of the reasons why the model has attracted wide attention in optimisation is that it is a particularly simple instance of a so-called Np-complete problem

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