Fix issue on Ackley Function

[ljvmiranda921]

• PySwarms version: 0.1.5
• Python version: 2.7
• Operating System: Linux

Description

It seems that the Ackley function is not working on Python 2.7 version

def ackley_func(x):
    if not np.logical_and(x >= -32, x <= 32).all():
        raise ValueError('Input for Ackley function must be within [-32, 32].')

    d = x.shape[1]
    j = (-20.0 * np.exp(-0.2 * np.sqrt((1/d) * (x**2).sum(axis=1)))
        - np.exp((1/d) * np.cos(2 * np.pi * x).sum(axis=1))
        + 20.0
        + np.exp(1))

    return j

When given an input np.zeros([3,2]), most Python 3.X versions return something that isclose to np.zeros(3). But when ran against a Python 2.7.X version, we're getting [1.718, 1.718, 1.718]

[ljvmiranda921]

Fixed. Just change to float(d). Read more here