Function argmin::testfunctions::easom

pub fn easom<T>(param: &[T]) -> T where
    T: FromPrimitive + Float, 

Easom test function

Defined as

f(x_1, x_2) = - cos(x_1) * cos(x_2) * exp(-(x_1 - pi)^2 - (x_2 - pi)^2)

where x_i \in [-100, 100].

The global minimum is at f(x_1, x_2) = f(pi, pi) = -1.