Solved by LinjX in post #8 
              
              
                Sorry for reply you late. 
I can draw figure like this 
 [image] 
using code 
import numpy as np 
import matplotlib.pyplot as plt 
from mpl_toolkits.mplot3d import Axes3D
import copy

def Goldstein_price(x,y):
    '''
        range: [-2, 2]
        f(0,-1)=3
    '''
    A = (1+ ((x+y+1)**2) * (19-14…