Source code for niapy.problems.michalewicz
# encoding=utf8
"""Implementations of Michalewicz's function."""
import numpy as np
from niapy.problems.problem import Problem
__all__ = ['Michalewicz']
[docs]class Michalewicz(Problem):
r"""Implementations of Michalewicz's functions.
Date: 2018
Author: Klemen Berkovič
License: MIT
Function:
**High Conditioned Elliptic Function**
:math:`f(\textbf{x}) = \sum_{i=1}^D \left( 10^6 \right)^{ \frac{i - 1}{D - 1} } x_i^2`
**Input domain:**
The function can be defined on any input domain but it is usually
evaluated on the hypercube :math:`x_i ∈ [0, \pi]`, for all :math:`i = 1, 2,..., D`.
**Global minimum:**
at :math:`d = 2` :math:`f(\textbf{x}^*) = -1.8013` at :math:`\textbf{x}^* = (2.20, 1.57)`
at :math:`d = 5` :math:`f(\textbf{x}^*) = -4.687658`
at :math:`d = 10` :math:`f(\textbf{x}^*) = -9.66015`
LaTeX formats:
Inline:
$f(\textbf{x}) = - \sum_{i = 1}^{D} \sin(x_i) \sin\left( \frac{ix_i^2}{\pi} \right)^{2m}$
Equation:
\begin{equation} f(\textbf{x}) = - \sum_{i = 1}^{D} \sin(x_i) \sin\left( \frac{ix_i^2}{\pi} \right)^{2m} \end{equation}
Domain:
$0 \leq x_i \leq \pi$
Reference URL:
https://www.sfu.ca/~ssurjano/michal.html
"""
[docs] def __init__(self, dimension=4, lower=0.0, upper=np.pi, m=10, *args, **kwargs):
r"""Initialize Michalewicz 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.
m (float): Steepness of valleys and ridges. Recommended value is 10.
See Also:
:func:`niapy.problems.Problem.__init__`
"""
super().__init__(dimension, lower, upper, *args, **kwargs)
self.m = m
[docs] @staticmethod
def latex_code():
r"""Return the latex code of the problem.
Returns:
str: Latex code.
"""
return r'''$f(\textbf{x}) = - \sum_{i = 1}^{D} \sin(x_i) \sin\left( \frac{ix_i^2}{\pi} \right)^{2m}$'''
def _evaluate(self, x):
return -np.sum(np.sin(x) * np.sin((np.arange(1, self.dimension + 1) * x ** 2.0) / np.pi) ** (2.0 * self.m))