The Shekel function or also Shekel's foxholes is a multidimensional, multimodal, continuous, deterministic function commonly used as a test function for testing optimization techniques.[1]
The mathematical form of a function in [math]\displaystyle{ n }[/math] dimensions with [math]\displaystyle{ m }[/math] maxima is:
[math]\displaystyle{ f(\vec{x}) = \sum_{i = 1}^{m} \; \left( c_{i} + \sum\limits_{j = 1}^{n} (x_{j} - a_{ji})^2 \right)^{-1} }[/math]
or, similarly,
[math]\displaystyle{ f(x_1,x_2,...,x_{n-1},x_n) = \sum_{i = 1}^{m} \; \left( c_{i} + \sum\limits_{j = 1}^{n} (x_{j} - a_{ij})^2 \right)^{-1} }[/math]
Numerically certified global minima and the corresponding solutions were obtained using interval methods for up to [math]\displaystyle{ n = 10 }[/math].[2]
Shekel, J. 1971. "Test Functions for Multimodal Search Techniques." Fifth Annual Princeton Conference on Information Science and Systems.
Original source: https://en.wikipedia.org/wiki/Shekel function.
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