[Python] theta values for gradient descent not coherent

i made a gradient descent code but it doesnt seem to work well

import numpy as np
from random import randint,random
import matplotlib . pyplot as plt


def calculh(theta, X):
h = 0
h+=theta[0]*X # w*X
h+= theta[-1] # +b
return h


def calculY(sigma, h) :
return sigma(h) # sigma peut-etre tanh, signoide etc.


def erreurJ(theta, sigma):
somme = 0
somme = 1/4*(sigma(theta[1])**2+sigma(theta[0]+theta[1])**2)
return somme


def gradient(X, Y, Ysol, sigmaprime, h):
return ((Y-Ysol)*sigmaprime(h)*X ,(Y-Ysol)*sigmaprime(h)*1)
def grad(theta):
w,b = theta[0],theta[1]
#print(theta)
return [2*b**3+3*b**2*w+3*b*w**2-2*b+w**3-w,b**3+3*b**2*w+3*b*w**2-b+w**3-w]
# *X correspond a 0 ou 1 : nos 2 entrées ; *1 correspond a derivee de b

def pasfixe(theta, eta, epsilon, X, Y, Ysol, sigma, sigmaprime, h):
n=0
while np.linalg.norm(gradient(X, Y, Ysol, sigmaprime, h)) > epsilon and n<10000 :
for i in range(len(theta)) :
theta = theta - eta*gradient(X, Y, Ysol, sigmaprime, h)
h = calculh(theta, X)
Y = calculY(sigma, h)
n+=1
if theta>100 : ### cas de divergence
return [100,100],Y
return theta,Y

sigma = lambda z : z**2-1
sigmaprime = lambda z : 2*z
eta = 0.1

X = 1
Ysol = 0
listeY = []
listetheta = []
lst = [[3*random()*(-1)**randint(0,1),3*random()*(-1)**randint(0,1)] for i in range(5000)]
nb = 0
for i in lst:
nb+=1
if nb%50 == 0:
print(nb)
theta = i[:]
h = calculh(theta, X)
Y = calculY(sigma, h)
CalculTheta = pasfixe( theta, eta, 10**-4, X,Y, Ysol, sigma, sigmaprime, h)
listetheta.append(CalculTheta[0])
listeY.append(CalculTheta[1])


for i in range (len(listeY)):
listeY = round(listeY,2)
print (listeY)

for i in range (len(listetheta)):
for j in range(2):
listetheta[j] = round(listetheta[j],2)
print (listetheta)

for i in range(len(lst)):
if [int(listetheta[0]),int(listetheta[1])] in [[-2,1]]:
plt.plot(lst[0],lst[1],"bo")
elif [int(listetheta[0]),int(listetheta[1])] in [[2,-1]]:
plt.plot(lst[0],lst[1],"co")
elif [int(listetheta[0]),int(listetheta[1])] in [[0,-1]]:
plt.plot(lst[0],lst[1],"go")
elif [int(listetheta[i][0]),int(listetheta[i][1])] in [[0,1]]:
plt.plot(lst[i][0],lst[i][1],"mo")
elif int(listetheta[i][0])**2 +int(listetheta[i][1])**2 >= 10:
plt.plot(lst[i][0],lst[i][1],"ro")

plt.show()


in the end i make a graph with the bias and weight values ans each point is colored in function of what the theta (weight,bias) value given at the beginning of the loop is converging to. [URL='https://i.sstatic.net/W5ivHcwX.png']the graph i am supposed to have[/URL]

i tried to calculate the gradient myself but it didnt work as well. i am supposed to get a graph like this one

[url="https://stackoverflow.com/questions/79440021/theta-values-for-gradient-descent-not-coherent"]Continue reading...[/url][/i][/i][/i][/i][/i][/i][/i][/i]