# Copyright (c) Facebook, Inc. and its affiliates.
#
# This source code is licensed under the MIT license found in the
# LICENSE file in the root directory of this source tree.
import numpy as np
import torch
import torch.nn as nn
import torch.nn.functional as F
from fairseq import utils
from fairseq.data import encoders
class RobertaHubInterface(nn.Module):
"""A simple PyTorch Hub interface to RoBERTa.
Usage: https://github.com/pytorch/fairseq/tree/master/examples/roberta
"""
def __init__(self, cfg, task, model):
super().__init__()
self.cfg = cfg
self.task = task
self.model = model
self.bpe = encoders.build_bpe(cfg.bpe)
# this is useful for determining the device
self.register_buffer("_float_tensor", torch.tensor([0], dtype=torch.float))
@property
def device(self):
return self._float_tensor.device
def encode(
self, sentence: str, *addl_sentences, no_separator=False
) -> torch.LongTensor:
"""
BPE-encode a sentence (or multiple sentences).
Every sequence begins with a beginning-of-sentence (`<s>`) symbol.
Every sentence ends with an end-of-sentence (`</s>`) and we use an
extra end-of-sentence (`</s>`) as a separator.
Example (single sentence): `<s> a b c </s>`
Example (sentence pair): `<s> d e f </s> </s> 1 2 3 </s>`
The BPE encoding follows GPT-2. One subtle detail is that the GPT-2 BPE
requires leading spaces. For example::
>>> roberta.encode('Hello world').tolist()
[0, 31414, 232, 2]
>>> roberta.encode(' world').tolist()
[0, 232, 2]
>>> roberta.encode('world').tolist()
[0, 8331, 2]
"""
bpe_sentence = "<s> " + self.bpe.encode(sentence) + " </s>"
for s in addl_sentences:
bpe_sentence += " </s>" if not no_separator else ""
bpe_sentence += " " + self.bpe.encode(s) + " </s>"
tokens = self.task.source_dictionary.encode_line(
bpe_sentence, append_eos=False, add_if_not_exist=False
)
return tokens.long()
def decode(self, tokens: torch.LongTensor):
assert tokens.dim() == 1
tokens = tokens.numpy()
if tokens[0] == self.task.source_dictionary.bos():
tokens = tokens[1:] # remove <s>
eos_mask = tokens == self.task.source_dictionary.eos()
doc_mask = eos_mask[1:] & eos_mask[:-1]
sentences = np.split(tokens, doc_mask.nonzero()[0] + 1)
sentences = [
self.bpe.decode(self.task.source_dictionary.string(s)) for s in sentences
]
if len(sentences) == 1:
return sentences[0]
return sentences
def extract_features(
self, tokens: torch.LongTensor, return_all_hiddens: bool = False
) -> torch.Tensor:
if tokens.dim() == 1:
tokens = tokens.unsqueeze(0)
if tokens.size(-1) > self.model.max_positions():
raise ValueError(
"tokens exceeds maximum length: {} > {}".format(
tokens.size(-1), self.model.max_positions()
)
)
features, extra = self.model(
tokens.to(device=self.device),
features_only=True,
return_all_hiddens=return_all_hiddens,
)
if return_all_hiddens:
# convert from T x B x C -> B x T x C
inner_states = extra["inner_states"]
return [inner_state.transpose(0, 1) for inner_state in inner_states]
else:
return features # just the last layer's features
def register_classification_head(
self, name: str, num_classes: int = None, embedding_size: int = None, **kwargs
):
self.model.register_classification_head(
name, num_classes=num_classes, embedding_size=embedding_size, **kwargs
)
def predict(self, head: str, tokens: torch.LongTensor, return_logits: bool = False):
features = self.extract_features(tokens.to(device=self.device))
logits = self.model.classification_heads[head](features)
if return_logits:
return logits
return F.log_softmax(logits, dim=-1)
def extract_features_aligned_to_words(
self, sentence: str, return_all_hiddens: bool = False
) -> torch.Tensor:
"""Extract RoBERTa features, aligned to spaCy's word-level tokenizer."""
from fairseq.models.roberta import alignment_utils
from spacy.tokens import Doc
nlp = alignment_utils.spacy_nlp()
tokenizer = alignment_utils.spacy_tokenizer()
# tokenize both with GPT-2 BPE and spaCy
bpe_toks = self.encode(sentence)
spacy_toks = tokenizer(sentence)
spacy_toks_ws = [t.text_with_ws for t in tokenizer(sentence)]
alignment = alignment_utils.align_bpe_to_words(self, bpe_toks, spacy_toks_ws)
# extract features and align them
features = self.extract_features(
bpe_toks, return_all_hiddens=return_all_hiddens
)
features = features.squeeze(0)
aligned_feats = alignment_utils.align_features_to_words(
self, features, alignment
)
# wrap in spaCy Doc
doc = Doc(
nlp.vocab,
words=["<s>"] + [x.text for x in spacy_toks] + ["</s>"],
spaces=[True]
+ [x.endswith(" ") for x in spacy_toks_ws[:-1]]
+ [True, False],
)
assert len(doc) == aligned_feats.size(0)
doc.user_token_hooks["vector"] = lambda token: aligned_feats[token.i]
return doc
def fill_mask(self, masked_input: str, topk: int = 5):
masked_token = "<mask>"
assert (
masked_token in masked_input and masked_input.count(masked_token) == 1
), "Please add one {0} token for the input, eg: 'He is a {0} guy'".format(
masked_token
)
text_spans = masked_input.split(masked_token)
text_spans_bpe = (
(" {0} ".format(masked_token))
.join([self.bpe.encode(text_span.rstrip()) for text_span in text_spans])
.strip()
)
tokens = self.task.source_dictionary.encode_line(
"<s> " + text_spans_bpe + " </s>",
append_eos=False,
add_if_not_exist=False,
)
masked_index = (tokens == self.task.mask_idx).nonzero(as_tuple=False)
if tokens.dim() == 1:
tokens = tokens.unsqueeze(0)
with utils.model_eval(self.model):
features, extra = self.model(
tokens.long().to(device=self.device),
features_only=False,
return_all_hiddens=False,
)
logits = features[0, masked_index, :].squeeze()
prob = logits.softmax(dim=0)
values, index = prob.topk(k=topk, dim=0)
topk_predicted_token_bpe = self.task.source_dictionary.string(index)
topk_filled_outputs = []
for index, predicted_token_bpe in enumerate(
topk_predicted_token_bpe.split(" ")
):
predicted_token = self.bpe.decode(predicted_token_bpe)
# Quick hack to fix https://github.com/pytorch/fairseq/issues/1306
if predicted_token_bpe.startswith("\u2581"):
predicted_token = " " + predicted_token
if " {0}".format(masked_token) in masked_input:
topk_filled_outputs.append(
(
masked_input.replace(
" {0}".format(masked_token), predicted_token
),
values[index].item(),
predicted_token,
)
)
else:
topk_filled_outputs.append(
(
masked_input.replace(masked_token, predicted_token),
values[index].item(),
predicted_token,
)
)
return topk_filled_outputs
def disambiguate_pronoun(self, sentence: str) -> bool:
"""
Usage::
>>> disambiguate_pronoun('The _trophy_ would not fit in the brown suitcase because [it] was too big.')
True
>>> disambiguate_pronoun('The trophy would not fit in the brown suitcase because [it] was too big.')
'The trophy'
"""
assert hasattr(
self.task, "disambiguate_pronoun"
), "roberta.disambiguate_pronoun() requires a model trained with the WSC task."
with utils.model_eval(self.model):
return self.task.disambiguate_pronoun(
self.model, sentence, use_cuda=self.device.type == "cuda"
)