About snake equation (3)

Three dimensional functions Gradient descent method

                                              

Its image and contour are as follows （ The blue dot in the center of the contour represents the minimum ）:

 

  Set the initial point as , Now the gradient is ：

 

Order step length , Then the next point is ：

You can see a step towards the minimum ：

 

 

  Set the initial point as    , Now the gradient is

Order step length , Then the next point is ：

  iteration Find the next point in the same way ：

 

  At this time, it is close to the minimum ：

So iterate 20 Next time , Almost found the minimum value ：