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Merge pull request #1384 from huggingface/encoding-qol

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Quality of life enhancements in encoding + patch MLM masking
This commit is contained in:
Lysandre Debut
2019-10-09 11:18:24 -04:00
committed by GitHub
parent 69629c4f0f 78ef1a9930
commit e84470ef81
17 changed files with 426 additions and 261 deletions
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181
transformers/tokenization_utils.py
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@@ -539,15 +539,9 @@ class PreTrainedTokenizer(object):
Returns:
Number of tokens added to sequences
"""
if pair:
initial_tokens_len = len(self.encode("This is a sequence") + self.encode("This is another"))
final_tokens_len = len(self.encode("This is a sequence", "This is another", add_special_tokens=True))
else:
initial_tokens_len = len(self.encode("This is a sequence"))
final_tokens_len = len(self.encode("This is a sequence", add_special_tokens=True))
return final_tokens_len - initial_tokens_len
token_ids_0 = []
token_ids_1 = []
return len(self.build_inputs_with_special_tokens(token_ids_0, token_ids_1 if pair else None))
def add_special_tokens(self, special_tokens_dict):
"""
@@ -699,7 +693,7 @@ class PreTrainedTokenizer(object):
add_special_tokens=False,
max_length=None,
stride=0,
truncate_first_sequence=True,
truncation_strategy='longest_first',
return_tensors=None,
**kwargs):
"""
@@ -719,9 +713,13 @@ class PreTrainedTokenizer(object):
max_length: if set to a number, will limit the total sequence returned so that it has a maximum length.
If there are overflowing tokens, those will be added to the returned dictionary
stride: if set to a number along with max_length, the overflowing tokens returned will contain some tokens
from the main sequence returned. The value of this argument defined the number of additional tokens.
truncate_first_sequence: if there is a specified max_length, this flag will choose which sequence
will be truncated.
from the main sequence returned. The value of this argument defines the number of additional tokens.
truncation_strategy: string selected in the following options:
- 'longest_first' (default) Iteratively reduce the inputs sequence until the input is under max_length
starting from the longest one at each token (when there is a pair of input sequences)
- 'only_first': Only truncate the first sequence
- 'only_second': Only truncate the second sequence
- 'do_not_truncate': Does not truncate (raise an error if the input sequence is longer than max_length)
return_tensors: (optional) can be set to 'tf' or 'pt' to return respectively TensorFlow tf.constant
or PyTorch torch.Tensor instead of a list of python integers.
**kwargs: passed to the `self.tokenize()` method
@@ -731,7 +729,7 @@ class PreTrainedTokenizer(object):
max_length=max_length,
add_special_tokens=add_special_tokens,
stride=stride,
truncate_first_sequence=truncate_first_sequence,
truncation_strategy=truncation_strategy,
return_tensors=return_tensors,
**kwargs)
@@ -743,7 +741,7 @@ class PreTrainedTokenizer(object):
add_special_tokens=False,
max_length=None,
stride=0,
truncate_first_sequence=True,
truncation_strategy='longest_first',
return_tensors=None,
**kwargs):
"""
@@ -762,9 +760,13 @@ class PreTrainedTokenizer(object):
max_length: if set to a number, will limit the total sequence returned so that it has a maximum length.
If there are overflowing tokens, those will be added to the returned dictionary
stride: if set to a number along with max_length, the overflowing tokens returned will contain some tokens
from the main sequence returned. The value of this argument defined the number of additional tokens.
truncate_first_sequence: if there is a specified max_length, this flag will choose which sequence
will be truncated.
from the main sequence returned. The value of this argument defines the number of additional tokens.
truncation_strategy: string selected in the following options:
- 'longest_first' (default) Iteratively reduce the inputs sequence until the input is under max_length
starting from the longest one at each token (when there is a pair of input sequences)
- 'only_first': Only truncate the first sequence
- 'only_second': Only truncate the second sequence
- 'do_not_truncate': Does not truncate (raise an error if the input sequence is longer than max_length)
return_tensors: (optional) can be set to 'tf' or 'pt' to return respectively TensorFlow tf.constant
or PyTorch torch.Tensor instead of a list of python integers.
**kwargs: passed to the `self.tokenize()` method
@@ -788,12 +790,11 @@ class PreTrainedTokenizer(object):
max_length=max_length,
add_special_tokens=add_special_tokens,
stride=stride,
truncate_first_sequence=truncate_first_sequence,
truncation_strategy=truncation_strategy,
return_tensors=return_tensors)
def prepare_for_model(self, ids, pair_ids=None, max_length=None, add_special_tokens=False, stride=0,
truncate_first_sequence=True, return_tensors=None):
truncation_strategy='longest_first', return_tensors=None):
"""
Prepares a sequence of input id, or a pair of sequences of inputs ids so that it can be used by the model.
It adds special tokens, truncates
@@ -810,41 +811,50 @@ class PreTrainedTokenizer(object):
to their model.
stride: window stride for overflowing tokens. Can be useful for edge effect removal when using sequential
list of inputs.
truncate_first_sequence: if set to `True` and an optional second list of input ids is provided,
alongside a specified `max_length`, will truncate the first sequence if the total size is superior
than the specified `max_length`. If set to `False`, will truncate the second sequence instead.
truncation_strategy: string selected in the following options:
- 'longest_first' (default) Iteratively reduce the inputs sequence until the input is under max_length
starting from the longest one at each token (when there is a pair of input sequences)
- 'only_first': Only truncate the first sequence
- 'only_second': Only truncate the second sequence
- 'do_not_truncate': Does not truncate (raise an error if the input sequence is longer than max_length)
return_tensors: (optional) can be set to 'tf' or 'pt' to return respectively TensorFlow tf.constant
or PyTorch torch.Tensor instead of a list of python integers.
Return:
a dictionary containing the `input_ids` as well as the `overflowing_tokens` if a `max_length` was given.
A Dictionary of shape::
{
input_ids: list[int],
overflowing_tokens: list[int] if a ``max_length`` is specified, else None
special_tokens_mask: list[int] if ``add_special_tokens`` if set to ``True``
}
With the fields:
``input_ids``: list of tokens to be fed to a model
``overflowing_tokens``: list of overflowing tokens if a max length is specified.
``special_tokens_mask``: if adding special tokens, this is a list of [0, 1], with 0 specifying special added
tokens and 1 specifying sequence tokens.
"""
pair = bool(pair_ids is not None)
len_ids = len(ids)
len_pair_ids = len(pair_ids) if pair else 0
encoded_inputs = {}
if max_length:
n_added_tokens = self.num_added_tokens(pair=pair) if add_special_tokens else 0
if pair and n_added_tokens + (len_pair_ids if truncate_first_sequence else len_ids) >= max_length:
logger.warning(
"You supplied a pair of sequence in which the sequence that will not be truncated is longer than the maximum specified length."
"This pair of sequences will not be truncated.")
else:
if n_added_tokens + len_ids + len_pair_ids > max_length:
if truncate_first_sequence or not pair:
encoded_inputs["overflowing_tokens"] = ids[max_length - len_pair_ids - n_added_tokens - stride:]
ids = ids[:max_length - len_pair_ids - n_added_tokens]
elif not truncate_first_sequence and pair:
encoded_inputs["overflowing_tokens"] = pair_ids[max_length - len_ids - n_added_tokens - stride:]
pair_ids = pair_ids[:max_length - len_ids - n_added_tokens]
else:
logger.warning(
"Cannot truncate second sequence as it is not provided. No truncation.")
total_len = len_ids + len_pair_ids + (self.num_added_tokens(pair=pair) if add_special_tokens else 0)
if max_length and total_len > max_length:
ids, pair_ids, overflowing_tokens = self.truncate_sequences(ids, pair_ids=pair_ids,
num_tokens_to_remove=total_len-max_length,
truncation_strategy=truncation_strategy,
stride=stride)
encoded_inputs["overflowing_tokens"] = overflowing_tokens
encoded_inputs["num_truncated_tokens"] = total_len - max_length
if add_special_tokens:
sequence = self.add_special_tokens_sequence_pair(ids, pair_ids) if pair else self.add_special_tokens_single_sequence(ids)
token_type_ids = self.create_token_type_ids_from_sequences(ids, pair_ids) if pair else [0] * len(sequence)
sequence = self.build_inputs_with_special_tokens(ids, pair_ids)
token_type_ids = self.create_token_type_ids_from_sequences(ids, pair_ids)
encoded_inputs["special_tokens_mask"] = self.get_special_tokens_mask(ids, pair_ids)
else:
sequence = ids + pair_ids if pair else ids
token_type_ids = [0] * len(ids) + ([1] * len(pair_ids) if pair else [])
@@ -861,20 +871,89 @@ class PreTrainedTokenizer(object):
encoded_inputs["input_ids"] = sequence
encoded_inputs["token_type_ids"] = token_type_ids
if max_length and len(encoded_inputs["input_ids"]) > max_length:
encoded_inputs["input_ids"] = encoded_inputs["input_ids"][:max_length]
encoded_inputs["token_type_ids"] = encoded_inputs["token_type_ids"][:max_length]
encoded_inputs["special_tokens_mask"] = encoded_inputs["special_tokens_mask"][:max_length]
return encoded_inputs
def create_token_type_ids_from_sequences(self, token_ids_0, token_ids_1):
def truncate_sequences(self, ids, pair_ids=None, num_tokens_to_remove=0, truncation_strategy='longest_first', stride=0):
"""Truncates a sequence pair in place to the maximum length.
truncation_strategy: string selected in the following options:
- 'longest_first' (default) Iteratively reduce the inputs sequence until the input is under max_length
starting from the longest one at each token (when there is a pair of input sequences).
Overflowing tokens only contains overflow from the first sequence.
- 'only_first': Only truncate the first sequence. raise an error if the first sequence is shorter or equal to than num_tokens_to_remove.
- 'only_second': Only truncate the second sequence
- 'do_not_truncate': Does not truncate (raise an error if the input sequence is longer than max_length)
"""
if num_tokens_to_remove <= 0:
return ids, pair_ids, []
if truncation_strategy == 'longest_first':
overflowing_tokens = []
for _ in range(num_tokens_to_remove):
if pair_ids is None or len(ids) > len(pair_ids):
overflowing_tokens = [ids[-1]] + overflowing_tokens
ids = ids[:-1]
else:
pair_ids = pair_ids[:-1]
window_len = min(len(ids), stride)
if window_len > 0:
overflowing_tokens = ids[-window_len:] + overflowing_tokens
elif truncation_strategy == 'only_first':
assert len(ids) > num_tokens_to_remove
window_len = min(len(ids), stride + num_tokens_to_remove)
overflowing_tokens = ids[-window_len:]
ids = ids[:-num_tokens_to_remove]
elif truncation_strategy == 'only_second':
assert pair_ids is not None and len(pair_ids) > num_tokens_to_remove
window_len = min(len(pair_ids), stride + num_tokens_to_remove)
overflowing_tokens = pair_ids[-window_len:]
pair_ids = pair_ids[:-num_tokens_to_remove]
elif truncation_strategy == 'do_not_truncate':
raise ValueError("Input sequence are too long for max_length. Please select a truncation strategy.")
else:
raise ValueError("Truncation_strategy should be selected in ['longest_first', 'only_first', 'only_second', 'do_not_truncate']")
return (ids, pair_ids, overflowing_tokens)
def create_token_type_ids_from_sequences(self, token_ids_0, token_ids_1=None):
logger.warning("This tokenizer does not make use of special tokens.")
if token_ids_1 is None:
return len(token_ids_0) * [0]
return [0] * len(token_ids_0) + [1] * len(token_ids_1)
def add_special_tokens_single_sequence(self, token_ids):
logger.warning("This tokenizer does not make use of special tokens. The sequence has been returned with no modification.")
return token_ids
def add_special_tokens_sequence_pair(self, token_ids_0, token_ids_1):
logger.warning("This tokenizer does not make use of special tokens. The two sequences have been concatenated.")
def build_inputs_with_special_tokens(self, token_ids_0, token_ids_1=None):
"""
Build model inputs from a sequence or a pair of sequence for sequence classification tasks
by concatenating and adding special tokens.
A RoBERTa sequence has the following format:
single sequence: <s> X </s>
pair of sequences: <s> A </s></s> B </s>
"""
logger.warning("This tokenizer does not make use of special tokens. Input is returned with no modification.")
if token_ids_1 is None:
return token_ids_0
return token_ids_0 + token_ids_1
def get_special_tokens_mask(self, token_ids_0, token_ids_1=None, already_has_special_tokens=False):
"""
Retrieves sequence ids from a token list that has no special tokens added. This method is called when adding
special tokens using the tokenizer ``prepare_for_model`` or ``encode_plus`` methods.
Args:
token_ids_0: list of ids (must not contain special tokens)
token_ids_1: Optional list of ids (must not contain special tokens), necessary when fetching sequence ids
for sequence pairs
already_has_special_tokens: (default False) Set to True if the token list is already formated with
special tokens for the model
Returns:
A list of integers in the range [0, 1]: 0 for a special token, 1 for a sequence token.
"""
return [0] * ((len(token_ids_1) if token_ids_1 else 0) + len(token_ids_0))
def convert_ids_to_tokens(self, ids, skip_special_tokens=False):
""" Converts a single index or a sequence of indices (integers) in a token "
(resp.) a sequence of tokens (str/unicode), using the vocabulary and added tokens.