Mistake in Ackley N. 3

[gbelouze]

I'm not sure how the critical point and optimal function value were found, but they do not make sense

f(x, y)≈-195.629028238419, at
x≈ ± 0.682584587365898
y≈ -0.36075325513719

The function value at that point is around -170. I found the experimental minimum through gradient descent to be

f(x, y) ≈ -186.4112127, at
x≈ ± 8e-10
y≈ -0.0068

Although I don't trust precisely the x coordinate since the gradient diverges around 0 and floating point approximation issues arise.