Source code for niapy.problems.happy_cat
# encoding=utf8
"""Implementation of Happy Cat function."""
import numpy as np
from niapy.problems.problem import Problem
__all__ = ['HappyCat']
[docs]class HappyCat(Problem):
r"""Implementation of Happy cat function.
Date: 2018
Author: Lucija Brezočnik
License: MIT
Function: **Happy cat function**
:math:`f(\mathbf{x}) = {\left |\sum_{i = 1}^D {x_i}^2 - D \right|}^{1/4} + (0.5 \sum_{i = 1}^D {x_i}^2 + \sum_{i = 1}^D x_i) / D + 0.5`
**Input domain:**
The function can be defined on any input domain but it is usually
evaluated on the hypercube :math:`x_i ∈ [-100, 100]`, for all :math:`i = 1, 2,..., D`.
**Global minimum:** :math:`f(x^*) = 0`, at :math:`x^* = (-1,...,-1)`
LaTeX formats:
Inline:
$f(\mathbf{x}) = {\left|\sum_{i = 1}^D {x_i}^2 -
D \right|}^{1/4} + (0.5 \sum_{i = 1}^D {x_i}^2 +
\sum_{i = 1}^D x_i) / D + 0.5$
Equation:
\begin{equation} f(\mathbf{x}) = {\left| \sum_{i = 1}^D {x_i}^2 -
D \right|}^{1/4} + (0.5 \sum_{i = 1}^D {x_i}^2 +
\sum_{i = 1}^D x_i) / D + 0.5 \end{equation}
Domain:
$-100 \leq x_i \leq 100$
Reference: http://bee22.com/manual/tf_images/Liang%20CEC2014.pdf &
Beyer, H. G., & Finck, S. (2012). HappyCat - A Simple Function Class Where Well-Known Direct Search Algorithms Do Fail.
In International Conference on Parallel Problem Solving from Nature (pp. 367-376). Springer, Berlin, Heidelberg.
"""
[docs] def __init__(self, dimension=4, lower=-100.0, upper=100.0, alpha=0.25, *args, **kwargs):
r"""Initialize Happy cat problem..
Args:
dimension (Optional[int]): Dimension of the problem.
lower (Optional[Union[float, Iterable[float]]]): Lower bounds of the problem.
upper (Optional[Union[float, Iterable[float]]]): Upper bounds of the problem.
See Also:
:func:`niapy.problems.Problem.__init__`
"""
super().__init__(dimension, lower, upper, *args, **kwargs)
self.alpha = alpha
[docs] @staticmethod
def latex_code():
r"""Return the latex code of the problem.
Returns:
str: Latex code.
"""
return r'''$f(\mathbf{x}) = {\left|\sum_{i = 1}^D {x_i}^2 -
D \right|}^{1/4} + (0.5 \sum_{i = 1}^D {x_i}^2 +
\sum_{i = 1}^D x_i) / D + 0.5$'''
def _evaluate(self, x):
val1 = np.sum(np.abs(x * x - self.dimension) ** self.alpha)
val2 = np.sum((0.5 * x * x + x) / self.dimension)
return val1 + val2 + 0.5