Метод простой итерации для решения систем линейных уравнений

import numpy as np
 
def sort_diag_arr(a) :
    n = len(a)
    a = np.array(a)
    for i in range(n):
        ind = np.abs(a[i:, i:n]).argmax()
        row = ind // (n - i) + i
        col = ind % (n - i) + i 
        a[:,[i, col]] = a[:,[col, i]]
        a[[i, row], :] = a[[row, i], :]
    return a 
 
 
A = [
[1.7,2.8,1.9],
[2.1,3.4,1.8],
[4.2,-1.7,1.3]]
B = [0.7,1.1,2.8]
 
eps = 1e-3
 
a = np.array(A)
a = sort_diag_arr(a)
print(a)
diag = (1/np.diag(a)).reshape(-1,1)
a[np.diag_indices_from(a)] = 0.
a = np.hstack((-a, np.array(B).reshape(-1, 1))) * diag
x = a[:,-1].ravel()
x = np.append(x, 1)
 
tmp = x.copy() + eps
cnt = 0
while abs(x-tmp).sum() > eps:
    tmp = x.copy()
    x = a.dot(x)
    x = np.append(x, 1)
    cnt += 1
 
print(x[:-1].round(), cnt)

import numpy as np
 
def sort_diag_arr(a,b) :
    n = len(a)
    a = np.array(a)
    b = np.array(b)
    for i in range(n):
        ind = np.abs(a[i:, i:n]).argmax()
        row = ind // (n - i) + i
        col = ind % (n - i) + i 
        a[:,[i, col]] = a[:,[col, i]]
        a[[i, row], :] = a[[row, i], :]
        b[i], b[row] = b[row], b[i]
    return a, b
 
 
A = [
[1.7,2.8,1.9],
[2.1,3.4,1.8],
[4.2,-1.7,1.3]]
B = [0.7,1.1,2.8]
 
eps = 1e-3
 
a, b = sort_diag_arr(A,B)
diag = (1/np.diag(a)).reshape(-1,1)
a[np.diag_indices_from(a)] = 0.
a = np.hstack((-a, b.reshape(-1, 1))) * diag
x = a[:,-1].ravel()
x = np.append(x, 1)
 
tmp = x.copy() + eps
cnt = 0
while abs(x-tmp).sum() > eps:
    tmp = x.copy()
    x = a.dot(x)
    x = np.append(x, 1)
    cnt += 1
 
print(x[:-1].round(3), cnt)

A = [[4.2, -1.7,  1.3],
 [ 2.1,  3.4,  1.8],
 [ 1.7,  2.8,  1.9]]
B = [2.8,1.1,0.7]
 
# точность итераций
eps = .001
x = []
n = len(A)
for j in range(n):
    k = A[j][j]
    for i in range(n):
        A[j][i] /= -k 
    A[j][j] = 0
    B[j] /= k 
 
# r - счетчик итераций
r = 0
x = B.copy()
tmp = sum(x) + 2*eps
while abs(sum(x)-tmp) > eps:
    tmp = sum(x)
    t = [0]*n
    for i in range(n):
        t[i] = sum(x[j]*A[i][j] for j in range(n)) + B[i]
    r += 1
    x = t.copy()
    print(x)
print(*(round(elem,3) for elem in x))
print(r)

def sort_diag_arr(a, b) :
    n = len(a)
    for i in range(n):
        ind, a[i:] = zip(*sorted(enumerate(a[i:]),
                             key=lambda x: -x[1][i]))
        b[i:] = [b[i+j] for j in ind]
    
    return a, b
 
 
A = [
[1.7,2.8,1.9],
[2.1,3.4,1.8],
[4.2,-1.7,1.3]]
B = [0.7,1.1,2.8]
A, B = sort_diag_arr(A, B)
 
# точность итераций
c = 3
eps = 1/10**c
x = []
n = len(A)
for j in range(n):
    k = A[j][j]
    for i in range(n):
        A[j][i] /= -k 
    A[j][j] = 0
    B[j] /= k 
 
# r - счетчик итераций
r = 0
x = B.copy()
tmp = sum(x) + 2*eps
while abs(sum(x)-tmp) > eps:
    tmp = sum(x)
    t = [0]*n
    for i in range(n):
        t[i] = sum(x[j]*A[i][j] for j in range(n)) + B[i]
    r += 1
    x = t.copy()
print(*(round(elem,3) for elem in x))
print(r)