gradient descent

Gradient descent is a very popular method for finding the maximum/ minimum point of a given function. It’s very simple yet powerful but may trap in the local minima. Here I try to find the minimum of the following function: $$ z= -( 4 \times e^{- ( (x-4)^2 +(y-4)^2 ) }+ 2 \times e^{- ( (x-2)^2 +(y-2)^2