Formula:
$$f(x) = \frac{1}{4000}\sum_{i=1}^{n}x_i^2 -
\prod_{i=1}^{n}\cos\left(\frac{x_i}{\sqrt{i}}\right) + 1$$
Global minimum: \(f(0, 0, ..., 0) = 0\)
Characteristics:
The Griewank function has a product term that introduces interdependence
among the variables. As dimension increases, the function becomes more
difficult to optimize.