class_docstr: Zacharov objective function.
  
  This class defines the Zacharov [1]_ global optimization problem. This
  is a multimodal minimization problem defined as follows:
  
  .. math::
  
      f_{\text{Zacharov}}(x) = \sum_{i=1}^{n} x_i^2 + \left ( \frac{1}{2}
                               \sum_{i=1}^{n} i x_i \right )^2
                               + \left ( \frac{1}{2} \sum_{i=1}^{n} i x_i 
                               \right )^4
  
  Here, :math:`n` represents the number of dimensions and
  :math:`x_i \in [-5, 10]` for :math:`i = 1, ..., n`.
  
  *Global optimum*: :math:`f(x) = 0` for :math:`x_i = 0` for
  :math:`i = 1, ..., n`
  
  .. [1] Jamil, M. & Yang, X.-S. A Literature Survey of Benchmark Functions
  For Global Optimization Problems Int. Journal of Mathematical Modelling
  and Numerical Optimisation, 2013, 4, 150-194.
code: def fun(self, x, *args):
      self.nfev += 1
  
      u = sum(x**2)
      v = sum(arange(1, self.N + 1) * x)
      return u + (0.5 * v) ** 2 + (0.5 * v) ** 4
  
imports: from numpy import abs, sum, sign, arange
  from .go_benchmark import Benchmark
label_desc: Use image node_id 2 for calling the Zacharov obj's underlying member method code with example usage: obj.fun(x) and returns: unknown