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.
The mathematical form of a function in dimensions with maxima is:
or, similarly,
Numerically certified global minima and the corresponding solutions were obtained using interval methods for up to .
Shekel, J. 1971. "Test Functions for Multimodal Search Techniques." Fifth Annual Princeton Conference on Information Science and Systems.