numba TypingError: Cannot unify array(float64, 1d, C) and float64 for 'v_new.2' - global-variables

Question

I'm making value function iteration code for economics study, using python and numba package.
Here's simple description of my problem:
I want to solve maximization problem using brent_max,(similar to scipy.optimization) for kp, given k, v while it converges.
kp is 'next state of k', and it is used for upper bound of maximization problem. so after brent_max calculate the value of kp, I want to save and use it again. That's why I used global option.
Here's my code for the problem and error message.
opt_growth_data = [('α', float64),
('β', float64),
('γ', float64),
('δ', float64),
('grid', float64[:])]
#jitclass(opt_growth_data)
class OptimalGrowth_VI:
def __init__(self, α=0.4, β=0.96, γ=2.0, δ=0.1, grid_max=10, grid_size=500):
self.α, self.β, self.γ, self.δ = α, β, γ, δ
self.grid = np.linspace(0.1, grid_max, grid_size)
def f(self, k):
return k**self.α
def u(self, c):
return c**(1-self.γ) / (1-self.γ)
def objective(self, k, kp, v_array):
f, u, β, δ = self.f, self.u, self.β, self.δ
v = lambda x: interp(self.grid, v_array, x)
return u(f(k) + (1-δ)*k -kp) + β*v(kp)
#njit
def T(v, og_VI):
k0 = og_VI.grid
v_greedy = np.empty_like(v)
v_new = np.empty_like(v)
f, δ = og_VI.f, og_VI.δ
for i in range(len(og_VI.grid)):
if i == 1:
k = k0[i]
else:
k = kp[i]
lower = 1e-10
upper = f(k) + (1-δ)*k
result = brent_max(og_VI.objective, lower, upper, args=(k,v))
v_greedy, v_new = result[0], result[1]
return v_greedy, v_new
def solve_model_VI(og_VI, tol=1e-4, max_iter=1000, print_skip=20):
v = og_VI.grid
i = 0
error = tol + 1
while i < max_iter and error > tol:
v_greedy, v_new = T(v, og_VI)
error = np.max(np.abs(v - v_new))
i += 1
if i % print_skip == 0:
print(f"Error at iteration {i} is {error}.")
global kp
kp = v_greedy
v = v_new
if i == max_iter:
print("Failed to converge!")
if i < max_iter:
print(f"\nConverged in {i} iterations.")
return v_greedy, v_new
og_VI = OptimalGrowth_VI()
k_opt_VI, k_solution = solve_model_VI(og_VI)
TypingError Traceback (most recent call last)
Input In [51], in <module>
1 og_VI = OptimalGrowth_VI()
----> 2 k_opt_VI, k_solution = solve_model_VI(og_VI)
Input In [49], in solve_model_VI(og_VI, tol, max_iter, print_skip)
4 error = tol + 1
6 while i < max_iter and error > tol:
----> 7 v_greedy, v_new = T(v, og_VI)
8 error = np.max(np.abs(v - v_new))
9 i += 1
TypingError: Failed in nopython mode pipeline (step: nopython frontend)
Cannot unify array(float64, 1d, C) and float64 for 'v_new.2', defined at /var/folders/yl/t420gknx17d8ppt9jgws8v700000gn/T/ipykernel_19631/2325054440.py (21)
File "../../../../../var/folders/yl/t420gknx17d8ppt9jgws8v700000gn/T/ipykernel_19631/2325054440.py", line 21:
<source missing, REPL/exec in use?>
During: typing of assignment at /var/folders/yl/t420gknx17d8ppt9jgws8v700000gn/T/ipykernel_19631/2325054440.py (21)
File "../../../../../var/folders/yl/t420gknx17d8ppt9jgws8v700000gn/T/ipykernel_19631/2325054440.py", line 21:
<source missing, REPL/exec in use?>
I don't know what is incorrect in my code. Is it related to numba, or do I made completely incorrect code?
It's related to economic problem, so I made a question to economics stack exchange but could not get an answer. I would be very grateful if you could help even if it bothers you.
I refer to
https://python.quantecon.org/optgrowth.html and
https://python.quantecon.org/optgrowth_fast.html
. thank you for your help.