[BUG]: cec2021 F2 has abnormal optimal value.

[SkyLull]

Description of the bug

In short:

F22021 should have a global optimal value = 1100.0, but I found much more space that has even lower values.

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In detail:

The plotted function of F22021 looked like this:

The very little red dot near the middle (located at (2.0990197e+01, -2.3188216e+01), right as provided) should have the global optimal value of 1100.0 (equals bias), but as the plot clearly showed, much more space has a value lower than 1100.0.
For example, the red dot located at (94.14767894, 2.33460048) near the right side solved for a value of 23.98, there even exists a point (99.31320785, -0.51136206) that solved for a value of -32.35

I suppose this is not the intended outcome?

In case I did something wrong that I couldn't find myself due to the lack of domain knowledge, here is the same plot from other angles:

Steps To Reproduce

I use this code to draw the plot:

import numpy as np
import matplotlib.pyplot as plt
import opfunu.cec_based


if __name__ == '__main__':
    dim = 2
    eval_func = opfunu.cec_based.F22021(ndim=2)
    bound = {"upper": 100.0,
             "lower": -100.0}

    # Create a meshgrid for visualization
    x = np.linspace(bound["lower"], bound["upper"], 300)
    y = np.linspace(bound["lower"], bound["upper"], 300)
    X, Y = np.meshgrid(x, y)

    Z = np.zeros_like(X)
    for i in range(len(x)):
        for j in range(len(y)):
            Z[i, j] = eval_func.evaluate([X[i, j], Y[i, j]])

    fig = plt.figure()
    ax = fig.add_subplot(111, projection='3d')
    ax.plot_surface(X, Y, Z, cmap='viridis')
    ax.set_xlabel('x')
    ax.set_ylabel('y')
    ax.set_zlabel('z')

    print("f_global = ", eval_func.f_global)

    ax.scatter(2.0990197e+01, -2.3188216e+01, 1100., color='red')

    plt.show()

Additional Information

The version of main packages:
Python 3.9.13
Cython 3.0.6
matplotlib 3.8.2
numpy 1.26.2
opfunu 1.0.1

using Windows 11 22H2

[thieu1995]

Hi @SkyLull,

Please install the previous version 1.0.0. This bug will be gone. This latest version has this bug but I haven't had time to fix it.