def J_N(x, mu, N, discount_factor=0.99): # computes J(mu,N,x)
if N < 0:
print("N cannot be negative !")
exit()
elif N == 0:
return 0
else:
new_state = env.f(x, mu(x))
r = env.rewards[new_state[0]][new_state[1]]
return r + discount_factor * J_N(env.f(x, mu(x)), mu, N - 1)
def optimal_policy(N):
"""
compute the optimal policy for the environnment
"""
""" exact probability """
p = {}
""" exact reward"""
r = {}
for x in env.state_space:
for u in env.action_space:
for next_state in env.state_space:
p[(x, u, next_state)] = 0
new_state = env.f(x, u)
p[(x, u, new_state)] = 1
r[(x, u)] = env.rewards[new_state[0]][new_state[1]]
""" compute the exact optimal policy """
Q = {}
for x in env.state_space:
for u in env.action_space:
Q[(x, u)] = Q_N(p, r, x, u, N)
# return determine_optimal_policy_from_Q(Q)
return Q
def influence_of_T_on_Q(T, N):
"""
display the difference between the Q calculated with the MDP structure
and the Q calculated with the exact p and r
"""
# exact probability
p = {}
# exact reward
r = {}
# instantiate the exact probability and reward function
for x in env.state_space:
for u in env.action_space:
for next_state in env.state_space:
p[(x, u, next_state)] = 0
new_state = env.f(x, u)
p[(x, u, new_state)] = 1
r[(x, u)] = env.rewards[new_state[0]][new_state[1]]
Q = {}
for x in env.state_space:
for u in env.action_space:
history, p_appr, r_appr = tj.create_trajectory((3, 0), T)
Q_optimal = round(fn.Q_N(p, r, x, u, N), 2)
Q_learned = round(fn.Q_N(p_appr, r_appr, x, u, N), 2)
Q[(x, u)] = (Q_optimal, Q_learned)
for key in list(Q.keys()):
diff = abs(Q[key][0] - Q[key][1])
str_x = "(x,u) = " + str(key) + " | Q_exact = " + str(Q[key][0]) + " | Q_appr = " + str(Q[key][1]) + " | diff = " + str(diff)
print(str_x)
return Q
def J_N(x, mu, N, discount_factor=0.99):
"""
computes J state-value recurrence function with policy ยต
"""
if N < 0:
print("N cannot be negative !")
return None
elif N == 0:
return 0
else:
new_state = env.f(x, mu[x])
return env.rewards[new_state[0]][new_state[1]] + discount_factor*J_N(new_state, mu, N-1)
def J_N(x, mu, r, N, discount_factor=0.99):
"""
computes J state-value recurrence function
"""
if N < 0:
print("N cannot be negative !")
exit()
elif N == 0:
return 0
else:
return r[
(x, mu[x])] + discount_factor * J_N(env.f(x, mu[x]), mu, r, N - 1)
def protocol_1(discount_factor=0.99, alpha=0.05, epsilon=0.25):
"""
first experimental protocol
"""
error = []
Q = {}
# initialization
for x in env.state_space:
for u in env.action_space:
# initialize Q to 0 everywhere
Q[(x, u)] = 0
for episode in range(100):
# initial state
state = (3, 0)
for transition in range(1000):
action = None
p = np.random.default_rng().random()
# epsilon-greedy policy
if p < 1 - epsilon: # exploitation
action = get_max_action(Q, state)
else: # exploration
action = tj.policy()
next_state = env.f(state, action)
# extract reward associates with state x and action u
reward = env.rewards[next_state[0]][next_state[1]]
# compute the max value of Q for the state x'
maxQ = get_max_value(Q, next_state)
# update Q
Q[(state, action)] = (1 - alpha) * Q[
(state, action)] + alpha * (reward + discount_factor * maxQ)
state = next_state
print("episode : " + str(episode + 1))
error.append(display(Q))
return error
def protocol_3(discount_factor=0.99, alpha=0.05, epsilon=0.25):
"""
third experimental protocol
"""
error = []
Q = {}
for x in env.state_space:
for u in env.action_space:
Q[(x, u)] = 0
for episode in range(100):
state = (3, 0)
buffer = []
for transition in range(1000):
action = None
p = np.random.default_rng().random()
if p < 1 - epsilon:
action = get_max_action(Q, state)
else:
action = tj.policy()
next_state = env.f(state, action)
reward = env.rewards[next_state[0]][next_state[1]]
# add the transition to the buffer
buffer.append((state, action, reward, next_state))
# update Q ten times using the buffer
for count in range(10):
index = np.random.randint(0, len(buffer))
x, u, r, next_x = buffer[index]
maxQ = get_max_value(Q, next_x)
Q[(state, action)] = (1 - alpha) * Q[(
state, action)] + alpha * (reward + discount_factor * maxQ)
state = next_state
print("episode : " + str(episode + 1))
error.append(display(Q))
return error
def create_trajectory(initial_x, T):
"""
creates ht (with ressources limitation algorithm)
"""
trajectory = []
N = {}
R = {}
Nx = {}
p = {}
r = {}
for x in env.state_space: # initializations for r and p computing
for u in env.action_space:
N[(x, u)] = 0
R[(x, u)] = 0
r[(x, u)] = -1000
for x0 in env.state_space:
Nx[(x, u, x0)] = 0
p[(x, u, x0)] = 0
x = initial_x
for i in range(T): # random trajectory computing
u = policy()
new_x = env.f(x, u)
rew = env.rewards[new_x[0]][new_x[1]]
trajectory.append([x, u, rew, new_x
]) # add current information to trajectory history
N[(x, u)] += 1
Nx[(x, u, new_x)] += 1
R[(x, u)] += rew
r[(x, u)] = R[(x, u)] / N[(x, u)] # mean of all the rewards
p[(x, u, new_x)] = Nx[(x, u, new_x)] / N[
(x, u)] # probability reaching state new_x with (x,u)
x = new_x
return trajectory, p, r
def protocol_2(discount_factor=0.99, epsilon=0.25):
"""
second experimental protocol
"""
error = []
Q = {}
for x in env.state_space:
for u in env.action_space:
Q[(x, u)] = 0
for episode in range(100):
alpha = 0.05
state = (3, 0)
for transition in range(1000):
action = None
p = np.random.default_rng().random()
if p < 1 - epsilon:
action = get_max_action(Q, state)
else:
action = tj.policy()
next_state = env.f(state, action)
reward = env.rewards[next_state[0]][next_state[1]]
maxQ = get_max_value(Q, next_state)
Q[(state, action)] = (1 - alpha) * Q[(state, action)] + alpha * (
reward + discount_factor * maxQ) # update Q
state = next_state
alpha *= 0.8
print("episode : " + str(episode + 1))
error.append(display(Q))
return error
def convergence_speed():
"""
Computes and display the convergence of p and r
"""
p_error = []
r_error = []
T = [i for i in range(100, 1200, 50)]
# we compute the error of the approximations for different trajectory length
for t in T:
history, p, r = tj.create_trajectory((3, 0), T)
p_sum = 0
r_sum = 0
# compute the error
for x in env.state_space:
for u in env.action_space:
new_state = env.f(x, u)
p_sum += (1 - p[(x, u, new_state)])
r_sum += abs(r[(x, u)] - env.rewards[new_state[0]][new_state[1]])
p_error.append(p_sum)
r_error.append(r_sum)
# plot the convergence of p and r, along T
fig, axs = plt.subplots(2, 1, figsize=(10, 10), constrained_layout=True)
axs[0].plot(T, p_error)
axs[0].set_ylabel('$p_{error}$')
axs[0].set_xlabel('T')
axs[0].set_title('Convergence speed of $\^p$')
axs[1].plot(T, r_error)
axs[1].set_ylabel('$r_{error}$')
axs[1].set_xlabel('T')
axs[1].set_title('Convergence speed of $\^r$')
plt.show()
return T, p_error, r_error
def Q_N(p, r, state, action, N, discount_factor=0.99): # computes Q state-action value recurrence function
if N < 0:
print("N can't be negative")
return None
elif N == 0:
return 0
else:
sum_Q = 0
for u in env.action_space:
# we are only looking for the state which are 'reachable' from x since others one will have p(x'|x,u)=0
x = env.f(state, u)
Qs = []
# store the reward recording for each action
for u1 in env.action_space:
Qs.append(Q_N(p, r, x, u1, N-1))
# look for which action gives best reward
max_Q = max(Qs)
# actualize the sum term in Qn recurrence formula
sum_Q += p[(state, action, x)]*max_Q
return r[(state, action)] + discount_factor*sum_Q
fig, ax = plt.subplots(figsize=(4, 4))
ax.axis('off')
cell_text = np.asarray(env.rewards, dtype=np.str)
colors = [["w" for i in range(env.m)] for j in range(env.n)]
# colors = [["w", "w", "w", "w", "w"], ["w", "w", "w", "w", "w"], ["w", "w", "w", "w", "w"],
# ["w", "w", "w", "w", "w"], ["w", "w", "w", "w", "w"]]
colors[position[0]][position[1]] = "r"
ax.table(cellText=cell_text, cellColours=colors, cellLoc='center', loc='center',
colWidths=[0.07, 0.07, 0.07, 0.07, 0.07])
plt.title(str_x, fontdict={'fontsize': 8})
plt.show()
if __name__ == '__main__':
s = (3, 0) # initial state
t = 0 # time
str_x = "state = " + str(s) + " | t = " + str(t)
print(str_x)
draw(s, str_x)
while True:
u = policy(s) # compute the policy with actual state
x = env.f(s, u, 0.1) # compute new state
r = round((0.99**t)*env.rewards[x[0]][x[1]], 4) # compute reward
s = x # update state
t += 1
str_x = "state = " + str(x) + " | action = " + str(u) + " | reward = " + str(r) + " | t = " + str(t)
print(str_x)
draw(s, str_x)
time.sleep(2) # in order to have time to visualizes the environment