Mistake in SchaffelN4

[gbelouze]

There are two mistakes, one in the LaTeX formula, and one in the loss implementation:

r"f(x, y)=0.5 + \frac{sin^2(cos(|x^2-y^2|))-0.5}{(1+0.001(x^2+y^2))^2}"
should be
r"f(x, y)=0.5 + \frac{cos^2(sin(|x^2-y^2|))-0.5}{(1+0.001(x^2+y^2))^2}"

def __call__(self, X):
    x, y = X
    res = 0.5 + (np.cos(np.sin(np.abs(x**2 + y**2)))**2 - 0.5)/(1 + 0.001*(x**2 + y**2))**2
    return res

should be

def f(self, X):
    x, y = X
    res = 0.5 + (np.cos(np.sin(np.abs(x**2 - y**2)))**2 - 0.5)/(1 + 0.001*(x**2 + y**2))**2
    return res

Also, I think it is Schaffer, not Schaffel...