def inference(self, tokens, token_types, valid_length, p_mask,
start_top_n: int = 5, end_top_n: int = 5):
"""Get the inference result with beam search
Parameters
----------
tokens
The input tokens. Shape (batch_size, sequence_length)
token_types
The input token types. Shape (batch_size, sequence_length)
valid_length
The valid length of the tokens. Shape (batch_size,)
p_mask
The mask which indicates that some tokens won't be used in the calculation.
Shape (batch_size, sequence_length)
start_top_n
The number of candidates to select for the start position.
end_top_n
The number of candidates to select for the end position.
Returns
-------
start_top_logits
The top start logits
Shape (batch_size, start_top_n)
start_top_index
Index of the top start logits
Shape (batch_size, start_top_n)
end_top_logits
The top end logits.
Shape (batch_size, end_top_n)
end_top_index
Index of the top end logits
Shape (batch_size, end_top_n)
"""
# Shape (batch_size, sequence_length, C)
if self.use_segmentation:
contextual_embeddings = self.backbone(tokens, token_types, valid_length)
else:
contextual_embeddings = self.backbone(tokens, valid_length)
scores = self.qa_outputs(contextual_embeddings)
start_scores = scores[:, :, 0]
end_scores = scores[:, :, 1]
start_logits = masked_logsoftmax(start_scores, mask=p_mask, axis=-1)
end_logits = masked_logsoftmax(end_scores, mask=p_mask, axis=-1)
# The shape of start_top_index will be (..., start_top_n)
start_top_logits, start_top_index = mx.npx.topk(start_logits, k=start_top_n, axis=-1,
ret_typ='both')
# Note that end_top_index and end_top_log_probs have shape (bsz, start_n_top, end_n_top)
# So that for each start position, there are end_n_top end positions on the third dim.
end_top_logits, end_top_index = mx.npx.topk(end_logits, k=end_top_n, axis=-1,
ret_typ='both')
return start_top_logits, start_top_index, end_top_logits, end_top_index
def get_end_logits(self, contextual_embedding, start_positions, p_mask):
"""
Parameters
----------
contextual_embedding
Shape (batch_size, sequence_length, C)
start_positions
Shape (batch_size, N)
We process multiple candidates simultaneously
p_mask
Shape (batch_size, sequence_length)
Returns
-------
end_logits
Shape (batch_size, N, sequence_length)
"""
# Select the features at the start_positions
# start_feature will have shape (batch_size, N, C)
start_features = select_vectors_by_position(contextual_embedding, start_positions)
# Concatenate the start_feature and the contextual_embedding
contextual_embedding = np.expand_dims(contextual_embedding, axis=1) # (B, 1, T, C)
start_features = np.expand_dims(start_features, axis=2) # (B, N, 1, C)
concat_features = np.concatenate([npx.broadcast_like(start_features,
contextual_embedding, 2, 2),
npx.broadcast_like(contextual_embedding,
start_features, 1, 1)],
axis=-1) # (B, N, T, 2C)
end_scores = self.end_scores(concat_features)
end_scores = np.squeeze(end_scores, -1)
end_logits = masked_logsoftmax(end_scores, mask=np.expand_dims(p_mask, axis=1),
axis=-1)
return end_logits
def forward(self, tokens, token_types, valid_length, p_mask):
"""
Parameters
----------
tokens
Shape (batch_size, seq_length)
The merged input tokens
token_types
Shape (batch_size, seq_length)
Token types for the sequences, used to indicate whether the word belongs to the
first sentence or the second one.
valid_length
Shape (batch_size,)
Valid length of the sequence. This is used to mask the padded tokens.
p_mask
The mask that is associated with the tokens.
Returns
-------
start_logits
Shape (batch_size, sequence_length)
The log-softmax scores that the position is the start position.
end_logits
Shape (batch_size, sequence_length)
The log-softmax scores that the position is the end position.
"""
# Get contextual embedding with the shape (batch_size, sequence_length, C)
if self.use_segmentation:
contextual_embeddings = self.backbone(tokens, token_types,
valid_length)
else:
contextual_embeddings = self.backbone(tokens, valid_length)
scores = self.qa_outputs(contextual_embeddings)
start_scores = scores[:, :, 0]
end_scores = scores[:, :, 1]
start_logits = masked_logsoftmax(start_scores, mask=p_mask, axis=-1)
end_logits = masked_logsoftmax(end_scores, mask=p_mask, axis=-1)
return start_logits, end_logits
def get_start_logits(self, contextual_embedding, p_mask):
"""
Parameters
----------
contextual_embedding
Shape (batch_size, sequence_length, C)
Returns
-------
start_logits
Shape (batch_size, sequence_length)
"""
start_scores = np.squeeze(self.start_scores(contextual_embedding), -1)
start_logits = masked_logsoftmax(start_scores, mask=p_mask, axis=-1)
return start_logits
