def call(self, inputs):
# PE_2i(p) = sin(p/10000^(2i/d_pos))
# PE_2i+1(p) = cos(p/10000^(2i/d_pos))
batch_size, seq_len, word_emb_dim = K.shape(inputs)[0], K.shape(
inputs)[1], K.shape(inputs)[2]
if not self.embedding_dim or self.method == 'add':
self.embedding_dim = word_emb_dim
t = 2 * K.arange(self.embedding_dim / 2, dtype='float32') / K.cast(
self.embedding_dim, dtype='float32')
embedding_wise_pos = 1. / K.pow(
10000., t) # 1/10000 ^(2i/d_pos) , shape = (p_dim/2, )
embedding_wise_pos = K.expand_dims(embedding_wise_pos,
0) # (1, p_dim/2)
word_wise_pos = K.cumsum(K.ones_like(inputs[:, :, 0]),
axis=1) # shape = [batch_size, seq_len]
word_wise_pos = K.expand_dims(word_wise_pos,
2) # (batch_size, seq_len, 1)
position_embedding = K.dot(
word_wise_pos,
embedding_wise_pos) # (batch_size, seq_len, p_dim/2)
position_embedding = K.expand_dims(position_embedding, 3)
position_embedding = K.reshape(K.concatenate(
[K.sin(position_embedding),
K.cos(position_embedding)], axis=-1),
shape=(batch_size, seq_len, -1))
if self.method == 'add':
return inputs + position_embedding
return K.concatenate([inputs, position_embedding], axis=-1)
def compute_loss_of_similarity(self, inputs):
y_true = self.get_labels_of_similarity(inputs) # 构建标签
y_pred = K.l2_normalize(inputs, axis=1) # 句向量归一化
similarities = K.dot(y_pred, K.transpose(y_pred)) # 相似度矩阵
similarities = similarities - K.eye(K.shape(y_pred)[0]) * 1e12 # 排除对角线
similarities = similarities * self.scale # scale
loss = K.categorical_crossentropy(
y_true, similarities, from_logits=True
)
return loss
def compute_loss_of_similarity(self, inputs, mask=None):
# _, _, _, y_pred, _ = inputs
_, _, _, _, y_pred = inputs # use last layer's logits
y_true = self.get_labels_of_similarity(y_pred) # 构建标签
y_pred = K.l2_normalize(y_pred, axis=1) # 句向量归一化
similarities = K.dot(y_pred, K.transpose(y_pred)) # 相似度矩阵
similarities = similarities - K.eye(K.shape(y_pred)[0]) * 1e12 # 排除对角线
similarities = similarities * 20 # scale
loss = K.categorical_crossentropy(
y_true, similarities, from_logits=True
)
self.add_metric(loss, 'sim_loss')
return loss
def call(self, inputs, mode='embedding'):
"""
embedding mode: 普通embedding， dense mode: 无bias的Dense，x dot embedding.T
:param inputs:
:param mode:
:return:
"""
self._mode = mode
if mode == 'embedding':
return super(Embedding, self).call(inputs)
kernel = K.transpose(self.embeddings)
return K.dot(inputs, kernel)
def compute_loss_of_scl(self, inputs, mask=None):
y_pred, y_true = inputs
label_mask = self.get_label_mask(y_true)
y_pred = K.l2_normalize(y_pred, axis=1) # 特征向量归一化
similarities = K.dot(y_pred, K.transpose(y_pred)) # 相似矩阵
similarities = similarities - K.eye(K.shape(y_pred)[0]) * 1e12 # 排除对角线,即 i == j
similarities = similarities / self.T # Temperature scale
similarities = K.exp(similarities) # exp
sum_similarities = K.sum(similarities, axis=-1, keepdims=True) # sum i != k
scl = similarities / sum_similarities
scl = K.log(scl + K.epsilon()) # sum log
scl = -K.sum(scl * label_mask, axis=1, keepdims=True) / (K.sum(label_mask, axis=1, keepdims=True) + K.epsilon())
return K.mean(scl)
