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Refactoring the generate() function (#6949)

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* first draft

* show design proposition for new generate method

* up

* make better readable

* make first version

* gpt2 tests pass

* make beam search for gpt2 work

* add first encoder-decoder code

* delete typo

* make t5 work

* save indermediate

* make bart work with beam search

* finish beam search bart / t5

* add default kwargs

* make more tests pass

* fix no bad words sampler

* some fixes and tests for all distribution processors

* fix test

* fix rag slow tests

* merge to master

* add nograd to generate

* make all slow tests pass

* speed up generate

* fix edge case bug

* small fix

* correct typo

* add type hints and docstrings

* fix typos in tests

* add beam search tests

* add tests for beam scorer

* fix test rag

* finish beam search tests

* move generation tests in seperate file

* fix generation tests

* more tests

* add aggressive generation tests

* fix tests

* add gpt2 sample test

* add more docstring

* add more docs

* finish doc strings

* apply some more of sylvains and sams comments

* fix some typos

* make fix copies

* apply lysandres and sylvains comments

* final corrections on examples

* small fix for reformer
This commit is contained in:
Patrick von Platen
2020-11-03 16:04:22 +01:00
committed by GitHub
parent b63beb743c
commit a1bbcf3f6c
38 changed files with 3022 additions and 1191 deletions
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src/transformers/generation_logits_process.py Normal file
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# coding=utf-8
# Copyright 2020 The HuggingFace Inc. team
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from abc import ABC
from typing import Iterable, List
import numpy as np
import torch
from torch.nn import functional as F
from .file_utils import add_start_docstrings
LOGITS_PROCESSOR_INPUTS_DOCSTRING = r"""
Args:
input_ids (:obj:`torch.LongTensor` of shape :obj:`(batch_size, sequence_length)`):
Indices of input sequence tokens in the vocabulary.
Indices can be obtained using :class:`~transformers.BertTokenizer`. See
:meth:`transformers.PreTrainedTokenizer.encode` and :meth:`transformers.PreTrainedTokenizer.__call__` for
details.
`What are input IDs? <../glossary.html#input-ids>`__
scores (:obj:`torch.FloatTensor` of shape :obj:`(batch_size, config.vocab_size)`):
Prediction scores of a language modeling head. These can be scores for each vocabulary token before SoftMax
or scores for each vocabulary token after SoftMax.
Return:
:obj:`torch.FloatTensor` of shape :obj:`(batch_size, config.vocab_size)`: The processed prediction scores.
"""
class LogitsProcessor(ABC):
"""Abstract base class for all logit processors that can be applied during generation."""
@add_start_docstrings(LOGITS_PROCESSOR_INPUTS_DOCSTRING)
def __call__(self, input_ids: torch.LongTensor, scores: torch.FloatTensor) -> torch.FloatTensor:
"""Torch method for processing logits."""
raise NotImplementedError(
f"{self.__class__} is an abstract class. Only classes inheriting this class can be called."
)
class LogitsWarper(ABC):
"""Abstract base class for all logit warpers that can be applied during generation with multinomial sampling."""
@add_start_docstrings(LOGITS_PROCESSOR_INPUTS_DOCSTRING)
def __call__(self, input_ids: torch.LongTensor, scores: torch.FloatTensor) -> torch.FloatTensor:
"""Torch method for warping logits."""
raise NotImplementedError(
f"{self.__class__} is an abstract class. Only classes inheriting this class can be called."
)
class LogitsProcessorList(list):
"""
This class can be used to create a list of :class:`~transformers.LogitsProcessor` or
:class:`~transformers.LogitsWarper` to subsequently process a :obj:`scores` input tensor. This class inherits from
list and adds a specific `__call__` method to apply each :class:`~transformers.LogitsProcessor` or
:class:`~transformers.LogitsProcessor` to the inputs.
"""
@add_start_docstrings(LOGITS_PROCESSOR_INPUTS_DOCSTRING)
def __call__(self, input_ids: torch.LongTensor, scores: torch.FloatTensor) -> torch.FloatTensor:
for processor in self:
scores = processor(input_ids, scores)
return scores
class MinLengthLogitsProcessor(LogitsProcessor):
r"""
:class:`transformers.LogitsProcessor` enforcing a min-length by setting EOS probability to 0.
Args:
min_length (:obj:`int`):
The minimum length below which the score of :obj:`eos_token_id` is set to :obj:`-float("Inf")`.
eos_token_id (:obj:`int`):
The id of the `end-of-sequence` token.
"""
def __init__(self, min_length: int, eos_token_id: int):
if not isinstance(min_length, int) or min_length < 0:
raise ValueError(f"`min_length` has to be a positive integer, but is {min_length}")
if not isinstance(eos_token_id, int) or eos_token_id < 0:
raise ValueError(f"`eos_token_id` has to be a positive integer, but is {eos_token_id}")
self.min_length = min_length
self.eos_token_id = eos_token_id
def __call__(self, input_ids: torch.LongTensor, scores: torch.FloatTensor) -> torch.FloatTensor:
cur_len = input_ids.shape[-1]
if cur_len < self.min_length:
scores[:, self.eos_token_id] = -float("inf")
return scores
class TemperatureLogitsWarper(LogitsWarper):
r"""
:class:`transformers.LogitsWarper` for temperature (exponential scaling output probability distribution).
Args:
temperature (:obj:`float`):
The value used to module the logits distribution.
"""
def __init__(self, temperature: float):
if not isinstance(temperature, float) or not (temperature > 0):
raise ValueError(f"`temperature` has to be a strictly positive float, but is {temperature}")
self.temperature = temperature
def __call__(self, input_ids: torch.Tensor, scores: torch.Tensor) -> torch.Tensor:
scores = scores / self.temperature
return scores
class RepetitionPenaltyLogitsProcessor(LogitsProcessor):
r"""
:class:`transformers.LogitsProcessor` enforcing an exponential penalty on repeated sequences.
Args:
repetition_penalty (:obj:`float`):
The parameter for repetition penalty. 1.0 means no penalty. See `this paper
<https://arxiv.org/pdf/1909.05858.pdf>`__ for more details.
"""
def __init__(self, penalty: float):
if not isinstance(penalty, float) or not (penalty > 0):
raise ValueError(f"`penalty` has to be a strictly positive float, but is {penalty}")
self.penalty = penalty
def __call__(self, input_ids: torch.LongTensor, scores: torch.FloatTensor) -> torch.FloatTensor:
for i in range(scores.shape[0]):
for previous_token in set(input_ids[i].tolist()):
# if score < 0 then repetition penalty has to be multiplied to reduce the previous token probability
if scores[i, previous_token] < 0:
scores[i, previous_token] *= self.penalty
else:
scores[i, previous_token] /= self.penalty
return scores
class TopPLogitsWarper(LogitsWarper):
"""
:class:`transformers.LogitsWarper` that performs top-p, i.e. restricting to top tokens summing to prob_cut_off <=
prob_cut_off.
Args:
top_p (:obj:`float`):
If set to < 1, only the most probable tokens with probabilities that add up to :obj:`top_p` or higher are
kept for generation.
filter_value (:obj:`float`, `optional`, defaults to :obj:`-float("Inf")`):
All filtered values will be set to this float value.
min_tokens_to_keep (:obj:`int`, `optional`, defaults to 1):
Minimum number of tokens that cannot be filtered.
"""
def __init__(self, top_p: float, filter_value: float = -float("Inf"), min_tokens_to_keep: int = 1):
if not isinstance(top_p, float) or (top_p < 0 or top_p > 1.0):
raise ValueError(f"`top_p` has to be a float > 0 and < 1, but is {top_p}")
self.top_p = top_p
self.filter_value = filter_value
self.min_tokens_to_keep = min_tokens_to_keep
def __call__(self, input_ids: torch.LongTensor, scores: torch.FloatTensor) -> torch.FloatTensor:
sorted_logits, sorted_indices = torch.sort(scores, descending=True)
cumulative_probs = torch.cumsum(F.softmax(sorted_logits, dim=-1), dim=-1)
# Remove tokens with cumulative top_p above the threshold (token with 0 are kept)
sorted_indices_to_remove = cumulative_probs > self.top_p
if self.min_tokens_to_keep > 1:
# Keep at least min_tokens_to_keep (set to min_tokens_to_keep-1 because we add the first one below)
sorted_indices_to_remove[..., : self.min_tokens_to_keep - 1] = 0
# Shift the indices to the right to keep also the first token above the threshold
sorted_indices_to_remove[..., 1:] = sorted_indices_to_remove[..., :-1].clone()
sorted_indices_to_remove[..., 0] = 0
# scatter sorted tensors to original indexing
indices_to_remove = sorted_indices_to_remove.scatter(1, sorted_indices, sorted_indices_to_remove)
scores[indices_to_remove] = self.filter_value
return scores
class TopKLogitsWarper(LogitsWarper):
r"""
:class:`transformers.LogitsWarper` that performs top-k, i.e. restricting to the k highest probability elements.
Args:
top_k (:obj:`int`):
The number of highest probability vocabulary tokens to keep for top-k-filtering.
filter_value (:obj:`float`, `optional`, defaults to :obj:`-float("Inf")`):
All filtered values will be set to this float value.
min_tokens_to_keep (:obj:`int`, `optional`, defaults to 1):
Minimum number of tokens that cannot be filtered.
"""
def __init__(self, top_k: int, filter_value: float = -float("Inf"), min_tokens_to_keep: int = 1):
if not isinstance(top_k, int) or top_k <= 0:
raise ValueError(f"`top_k` has to be a strictly positive integer, but is {top_k}")
self.top_k = top_k
self.filter_value = filter_value
self.min_tokens_to_keep = min_tokens_to_keep
def __call__(self, input_ids: torch.LongTensor, scores: torch.FloatTensor) -> torch.FloatTensor:
top_k = min(max(self.top_k, self.min_tokens_to_keep), scores.size(-1)) # Safety check
# Remove all tokens with a probability less than the last token of the top-k
indices_to_remove = scores < torch.topk(scores, top_k)[0][..., -1, None]
scores[indices_to_remove] = self.filter_value
return scores
class NoRepeatNGramLogitsProcessor(LogitsProcessor):
r"""
:class:`transformers.LogitsProcessor` that enforces no repetition of n-grams. See `Fairseq
<https://github.com/pytorch/fairseq/blob/a07cb6f40480928c9e0548b737aadd36ee66ac76/fairseq/sequence_generator.py#L345>`__.
Args:
ngram_size (:obj:`int`):
All ngrams of size :obj:`ngram_size` can only occur once.
"""
def __init__(self, ngram_size: int):
if not isinstance(ngram_size, int) or ngram_size <= 0:
raise ValueError(f"`ngram_size` has to be a strictly positive integer, but is {ngram_size}")
self.ngram_size = ngram_size
def __call__(self, input_ids: torch.LongTensor, scores: torch.FloatTensor) -> torch.FloatTensor:
num_batch_hypotheses = scores.shape[0]
cur_len = input_ids.shape[-1]
banned_batch_tokens = self._calc_banned_ngram_tokens(input_ids, num_batch_hypotheses, cur_len)
for i, banned_tokens in enumerate(banned_batch_tokens):
scores[i, banned_tokens] = -float("inf")
return scores
def _calc_banned_ngram_tokens(
self, prev_input_ids: torch.Tensor, num_hypos: int, cur_len: int
) -> List[Iterable[int]]:
"""Copied from fairseq for no_repeat_ngram in beam_search"""
if cur_len + 1 < self.ngram_size:
# return no banned tokens if we haven't generated no_repeat_ngram_size tokens yet
return [[] for _ in range(num_hypos)]
generated_ngrams = [{} for _ in range(num_hypos)]
for idx in range(num_hypos):
gen_tokens = prev_input_ids[idx].tolist()
generated_ngram = generated_ngrams[idx]
for ngram in zip(*[gen_tokens[i:] for i in range(self.ngram_size)]):
prev_ngram_tuple = tuple(ngram[:-1])
generated_ngram[prev_ngram_tuple] = generated_ngram.get(prev_ngram_tuple, []) + [ngram[-1]]
def _get_generated_ngrams(hypo_idx):
# Before decoding the next token, prevent decoding of ngrams that have already appeared
start_idx = cur_len + 1 - self.ngram_size
ngram_idx = tuple(prev_input_ids[hypo_idx, start_idx:cur_len].tolist())
return generated_ngrams[hypo_idx].get(ngram_idx, [])
banned_tokens = [_get_generated_ngrams(hypo_idx) for hypo_idx in range(num_hypos)]
return banned_tokens
class NoBadWordsLogitsProcessor(LogitsProcessor):
"""
:class:`transformers.LogitsProcessor` that enforces that specified sequences will never be sampled.
Args:
bad_words_ids (:obj:`List[List[int]]`):
List of list of token ids that are not allowed to be generated. In order to get the tokens of the words
that should not appear in the generated text, use :obj:`tokenizer(bad_word,
add_prefix_space=True).input_ids`.
eos_token_id (:obj:`int`):
The id of the `end-of-sequence` token.
"""
def __init__(self, bad_words_ids: Iterable[Iterable[int]], eos_token_id: int):
if not isinstance(bad_words_ids, List) or len(bad_words_ids) == 0:
raise ValueError(f"`bad_words_ids` has to be a non-emtpy list, but is {bad_words_ids}.")
if any(not isinstance(bad_word_ids, list) for bad_word_ids in bad_words_ids):
raise ValueError(f"`bad_words_ids` has to be a list of lists, but is {bad_words_ids}.")
if any(
any((not isinstance(token_id, (int, np.integer)) or token_id < 0) for token_id in bad_word_ids)
for bad_word_ids in bad_words_ids
):
raise ValueError(
f"Each list in `bad_words_ids` has to be a list of positive integers, but is {bad_words_ids}."
)
self.bad_words_ids = list(filter(lambda bad_token_seq: bad_token_seq != [eos_token_id], bad_words_ids))
for banned_token_seq in self.bad_words_ids:
assert len(banned_token_seq) > 0, "Banned words token sequences {} cannot have an empty list".format(
bad_words_ids
)
def __call__(self, input_ids: torch.LongTensor, scores: torch.FloatTensor) -> torch.FloatTensor:
banned_tokens = self._calc_banned_bad_words_ids(input_ids)
scores = self._set_scores_to_inf_for_banned_tokens(scores, banned_tokens)
return scores
def _tokens_match(self, prev_tokens: torch.LongTensor, tokens: List[int]) -> bool:
if len(tokens) == 0:
# if bad word tokens is just one token always ban it
return True
elif len(tokens) > len(prev_tokens):
# if bad word tokens are longer then prev input_ids they can't be equal
return False
elif prev_tokens[-len(tokens) :].tolist() == tokens:
# if tokens match
return True
else:
return False
def _calc_banned_bad_words_ids(self, prev_input_ids: Iterable[int]) -> Iterable[int]:
banned_tokens = []
for prev_input_ids_slice in prev_input_ids:
banned_tokens_slice = []
for banned_token_seq in self.bad_words_ids:
if self._tokens_match(prev_input_ids_slice, banned_token_seq[:-1]) is False:
# if tokens do not match continue
continue
banned_tokens_slice.append(banned_token_seq[-1])
banned_tokens.append(banned_tokens_slice)
return banned_tokens
def _set_scores_to_inf_for_banned_tokens(self, scores: torch.Tensor, banned_tokens: List[List[int]]) -> None:
"""
Modifies the scores in place by setting the banned token positions to `-inf`. Banned token is expected to be a
list of list of banned tokens to ban in the format [[batch index, vocabulary position],...
Args:
scores: logits distribution of shape (batch size, vocabulary size)
banned_tokens: list of list of tokens to ban of length (batch_size)
"""
banned_mask_list = []
for idx, batch_banned_tokens in enumerate(banned_tokens):
for token in batch_banned_tokens:
banned_mask_list.append([idx, token])
if not banned_mask_list:
return scores
banned_mask = torch.LongTensor(banned_mask_list)
indices = torch.ones(len(banned_mask))
# A sparse tensor is generated from a list of coordinates: [[0, 1], [0, 2], [2, 0]]. A conversion to dense tensor generates:
# [ 0 1 1 ]
# [ 0 0 0 ]
# [ 1 0 0 ]
banned_mask = (
torch.sparse.LongTensor(banned_mask.t(), indices, scores.size()).to(scores.device).to_dense().bool()
)
scores = scores.masked_fill(banned_mask, -float("inf"))
return scores