In [3]:
# Data
import numpy as np
# if __name__ == '__main__':
with open('data/text_data/japan.txt', 'r') as f:
txt = f.read()
X = []
y = []
char_to_idx = {char: i for i, char in enumerate(set(txt))}
idx_to_char = {i: char for i, char in enumerate(set(txt))}
X = [char_to_idx[x] for x in txt]
X = np.array(X)
y = [char_to_idx[x] for x in txt[1:]]
y.append(char_to_idx['.'])
y = np.array(y)
# # Data exploration
# X.shape, y.shape, X, y, txt.split()[:2],
# # set(txt),
# # for val, key in enumerate(set(txt)):
# # print(val, key)
# val2char = {val: key for val, key in enumerate(set(txt))}
# # val2char
In [4]:
# Model
import impl.layer as l
class RNN:
def __init__(self, D, H, L, char2idx, idx2char):
self.D = D
self.H = H
self.L = L
self.char2idx = char2idx
self.idx2char = idx2char
self.vocab_size = len(char2idx)
self.losses = {'train':[], 'smooth train':[]}
# Model parameters
m = dict(
Wxh=np.random.randn(D, H) / np.sqrt(D / 2.),
Whh=np.random.randn(H, H) / np.sqrt(H / 2.),
Why=np.random.randn(H, D) / np.sqrt(H / 2.),
bh=np.zeros((1, H)),
by=np.zeros((1, D))
)
self.model = []
for _ in range(self.L):
self.model.append(m)
def initial_state(self):
return np.zeros((1, self.H))
def forward(self, X, h, m):
Wxh, Whh, Why = m['Wxh'], m['Whh'], m['Why']
bh, by = m['bh'], m['by']
hprev = h.copy()
h = X @ Wxh + hprev @ Whh + bh
h, h_cache = l.tanh_forward(h)
y, y_cache = l.fc_forward(h, Why, by)
cache = X, Wxh, hprev, Whh, h_cache, y_cache
return y, h, cache
def backward(self, dy, dh, cache):
X, Wxh, hprev, Whh, h_cache, y_cache = cache
dh_next = dh.copy()
# Hidden to output gradient
dh, dWhy, dby = l.fc_backward(dy, y_cache)
dh += dh_next
dby = dby.reshape((1, -1))
# tanh
dh = l.tanh_backward(dh, h_cache)
# Hidden gradient
dbh = dh
dWhh = hprev.T @ dh
dWxh = X.T @ dh
dX = dh @ Wxh.T
dh = dh @ Whh.T
grad = dict(Wxh=dWxh, Whh=dWhh, Why=dWhy, bh=dbh, by=dby)
return dX, dh, grad
def train_forward(self, X_train, h):
ys, caches = [], []
h_init = h.copy()
h = []
for _ in range(self.L):
h.append(h_init.copy())
caches.append([])
for X in X_train:
X_one_hot = np.zeros(self.D)
X_one_hot[X] = 1.
y = X_one_hot.reshape(1, -1)
for layer in range(self.L):
y, h[layer], cache = self.forward(y, h[layer], self.model[layer])
caches[layer].append(cache)
ys.append(y)
return ys, caches
def cross_entropy(self, y_pred, y_train):
m = y_pred.shape[0]
prob = l.softmax(y_pred)
log_like = -np.log(prob[range(m), y_train])
data_loss = np.sum(log_like) / m
return data_loss # + reg_loss
def dcross_entropy(self, y_pred, y_train):
m = y_pred.shape[0]
grad_y = l.softmax(y_pred)
grad_y[range(m), y_train] -= 1.0
grad_y /= m
return grad_y
def loss_function(self, y_train, ys):
loss, dys = 0.0, []
for y_pred, y in zip(ys, y_train):
loss += self.cross_entropy(y_pred, y)
dy = self.dcross_entropy(y_pred, y)
dys.append(dy)
return loss, dys
def train_backward(self, dys, caches):
dh, grad, grads = [], [], []
for layer in range(self.L):
dh.append(np.zeros((1, self.H)))
grad.append({key: np.zeros_like(val) for key, val in self.model[layer].items()})
grads.append({key: np.zeros_like(val) for key, val in self.model[layer].items()})
for t in reversed(range(len(dys))):
dX = dys[t]
for layer in reversed(range(self.L)):
dX, dh[layer], grad[layer] = self.backward(dX, dh[layer], caches[layer][t])
for key in grad[0].keys():
grads[layer][key] += grad[layer][key]
return dX, grads
def test(self, X_seed, h, size):
chars = [self.idx2char[X_seed]]
idx_list = list(range(self.vocab_size))
X = X_seed
h_init = h.copy()
h = []
for _ in range(self.L):
h.append(h_init.copy())
for _ in range(size):
X_one_hot = np.zeros(self.D)
X_one_hot[X] = 1.
y = X_one_hot.reshape(1, -1)
for layer in range(self.L):
y, h[layer], _ = self.forward(y, h[layer], self.model[layer])
prob = l.softmax(y)
idx = np.random.choice(idx_list, p=prob.ravel())
chars.append(self.idx2char[idx])
X = idx
return ''.join(chars)
In [8]:
from sklearn.utils import shuffle as skshuffle
def get_minibatch(X, y, minibatch_size, shuffle):
minibatches = []
if shuffle:
X, y = skshuffle(X, y)
for i in range(0, X.shape[0], minibatch_size):
X_mini = X[i:i + minibatch_size]
y_mini = y[i:i + minibatch_size]
minibatches.append((X_mini, y_mini))
return minibatches
def adam_rnn(nn, X_train, y_train, alpha, mb_size, n_iter, print_after):
minibatches = get_minibatch(X_train, y_train, mb_size, shuffle=False)
M, R = [], []
for _ in range(nn.L):
M.append({k: np.zeros_like(v) for k, v in nn.model[0].items()})
R.append({k: np.zeros_like(v) for k, v in nn.model[0].items()})
beta1 = .9
beta2 = .999
idx = 0
state = nn.initial_state()
loss = np.log(len(set(X_train)))
eps = 1e-8
smooth_loss = 1.0 #-np.log(1.0 / len(set(X_train)))
for iter in range(1, n_iter + 1):
if idx >= len(minibatches):
idx = 0
state = nn.initial_state()
X_mini, y_mini = minibatches[idx]
idx += 1
ys, caches = nn.train_forward(X_mini, state)
loss, dys = nn.loss_function(y_mini, ys)
dX, grads = nn.train_backward(dys, caches)
nn.losses['train'].append(loss)
smooth_loss = 0.999 * smooth_loss + 0.001 * loss
nn.losses['smooth train'].append(smooth_loss)
for layer in range(nn.L):
for k in grads[0].keys(): #key, value: items
M[layer][k] = l.exp_running_avg(M[layer][k], grads[layer][k], beta1)
R[layer][k] = l.exp_running_avg(R[layer][k], grads[layer][k]**2, beta2)
m_k_hat = M[layer][k] / (1. - beta1**(iter))
r_k_hat = R[layer][k] / (1. - beta2**(iter))
nn.model[layer][k] -= alpha * m_k_hat / (np.sqrt(r_k_hat) + eps)
# Print loss and test sample
if iter % print_after == 0:
print('Iter-{} loss: {:.4f}'.format(iter, loss))
sample = nn.test(X_mini[0], state, size=mb_size*10)
print(sample)
return nn
In [25]:
vocab_size = len(char_to_idx)
# hyper parameters
time_step = 10 # width
num_layers = 1 # depth
n_iter = 13000 # epochs
alpha = 1e-3 # learning_rate
print_after = n_iter//10 # print loss, valid, and test
H = 64 # num_hidden_units in hidden layer
In [26]:
net = RNN(D=vocab_size, H=H, L=num_layers, char2idx=char_to_idx, idx2char=idx_to_char)
adam_rnn(nn=net, X_train=X, y_train=y, alpha=alpha, mb_size=time_step, n_iter=n_iter, print_after=print_after)
Out[26]:
In [24]:
# # Display the learning curve and losses for training, validation, and testing
# %matplotlib inline
# %config InlineBackend.figure_format = 'retina'
import matplotlib.pyplot as plt
plt.plot(net.losses['train'], label='Train loss')
plt.plot(net.losses['smooth train'], label='Smooth train loss')
plt.legend()
plt.show()
In [ ]: