def train_step(self, X_train, y_train, h):
ys, caches = [], []
total_loss = 0
grads = {k: np.zeros_like(v) for k, v in self.model.items()}
# forward pass and store values for bptt
for x, y in zip(X_train, y_train):
y_pred, h, cache = self._forward(x, h)
p = softmax(y_pred)
log_likelihood = -np.log(p[range(y_pred.shape[0]), y])
total_loss += np.sum(log_likelihood) / y_pred.shape[0]
ys.append(y_pred)
caches.append(cache)
total_loss /= X_train.shape[0]
# backprop through time
dh_next = np.zeros((1, self.h_size))
for t in reversed(range(len(X_train))):
grad, dh_next = self._backward(ys[t], y_train[t], dh_next,
caches[t])
# sum up the gradients for each time step
for k in grads.keys():
grads[k] += grad[k]
# clip vanishing/exploding gradients
for k, v in grads.items():
grads[k] = np.clip(v, -5.0, 5.0)
return loss, grads, h
def SoftmaxLoss(X, y):
m = y.shape[0]
p = softmax(X)
log_likelihood = -np.log(p[range(m), y])
loss = np.sum(log_likelihood) / m
dx = p.copy()
dx[range(m), y] -= 1
dx /= m
return loss, dx
def _backward(self, out, y, dh_next, cache):
X_onehot, h_prev = cache
# gradient of output from froward step
dout = softmax(out)
dout[range(len(y)), y] -= 1
# fully connected backward step
dWhy = X_onehot.T @ dout
dby = np.sum(dWhy, axis=0).reshape(1, -1)
dh = dout @ self.dWhy.T
# gradient through tanh
dh = dout * (1 - out**2)
# add up gradient from previous gradient
dh += dh_next
# hidden state
dbh = dh
dWhh = h_prev.T @ dh
dWxh = X_onehot.T @ dh
dh_next = dh @ Whh.T
grads = dict(Wxh=dWxh, Whh=dWhh, Why=dWhy, bh=dbh, by=dby)
return grads, dh_next
def predict(self, X):
X = self.forward(X)
return np.argmax(softmax(X), axis=1)
def evaluate(self, X, y):
out = self.forward(X)
loss, dout = self.loss_func(out, y)
return np.argmax(softmax(X), axis=1), loss
def predict(self, X):
X = self.forward(X)
# print(np.argmax(softmax(X), axis=1))
return softmax(X)
