import json
from transformers.tokenization_utils import PreTrainedTokenizer
from yacs.config import CfgNode
from openprompt.data_utils import InputFeatures
import re
from openprompt import Verbalizer
from typing import *
import torch
import torch.nn as nn
import torch.nn.functional as F
from openprompt.utils.logging import logger
[docs]class One2oneVerbalizer(Verbalizer):
r"""
The basic manually defined verbalizer class, this class is inherited from the :obj:`Verbalizer` class.
This class restrict the use of label words to one words per label. For a verbalzer with less constraints,
please use Basic ManualVerbalizer.
Args:
tokenizer (:obj:`PreTrainedTokenizer`): The tokenizer of the current pre-trained model to point out the vocabulary.
classes (:obj:`classes`): The classes (or labels) of the current task.
num_classes (:obj:`int`): Optional. The number of classes of the verbalizer. Only one of `classes` and `num_classes` should be used.
label_words (:obj:`Union[Sequence[str], Mapping[str, str]]`, optional): The label words that are projected by the labels.
prefix (:obj:`str`, optional): The prefix string of the verbalizer. (used in PLMs like RoBERTa, which is sensitive to prefix space)
multi_token_handler (:obj:`str`, optional): The handling strategy for multiple tokens produced by the tokenizer.
post_log_softmax (:obj:`bool`, optional): Whether to apply log softmax post processing on label_logits. Default to True.
"""
def __init__(self,
tokenizer: PreTrainedTokenizer,
num_classes: Optional[int] = None,
classes: Optional[List] = None,
label_words: Optional[Union[Sequence[str], Mapping[str, str]]] = None,
prefix: Optional[str] = " ",
multi_token_handler: Optional[str] = "first",
post_log_softmax: Optional[bool] = True,
):
super().__init__(tokenizer=tokenizer, num_classes=num_classes, classes=classes)
self.prefix = prefix
self.multi_token_handler = multi_token_handler
self.label_words = label_words
self.post_log_softmax = post_log_softmax
[docs] def on_label_words_set(self):
super().on_label_words_set()
self.label_words = self.add_prefix(self.label_words, self.prefix)
self.generate_parameters()
[docs] @staticmethod
def add_prefix(label_words, prefix):
r"""Add prefix to label words. For example, if a label words is in the middle of a template,
the prefix should be ``' '``.
Args:
label_words (:obj:`Union[Sequence[str], Mapping[str, str]]`, optional): The label words that are projected by the labels.
prefix (:obj:`str`, optional): The prefix string of the verbalizer.
Returns:
:obj:`Sequence[str]`: New label words with prefix.
"""
new_label_words = []
if isinstance(label_words[0], list):
assert max([len(w) for w in label_words]) == 1, "Providing multiple label words, you should use other verbalizers instead."
label_words = [w[0] for w in label_words]
for word in label_words:
if word.startswith("<!>"):
new_label_words.append(word.split("<!>")[1])
else:
new_label_words.append(prefix + word)
return new_label_words
[docs] def generate_parameters(self) -> List:
r"""In basic manual template, the parameters are generated from label words directly.
In this implementation, the label_words should not be tokenized into more than one token.
"""
words_ids = []
for word in self.label_words:
word_ids = self.tokenizer.encode(word, add_special_tokens=False)
if len(word_ids) > 1:
logger.warning("Word {} is split into multiple tokens: {}. \
If this is not what you expect, try using another word for this verbalizer" \
.format(word, self.tokenizer.convert_ids_to_tokens(word_ids)))
words_ids.append(word_ids)
max_len = max([len(ids) for ids in words_ids])
words_ids_mask = [[1]*len(ids) + [0]*(max_len-len(ids)) for ids in words_ids]
words_ids = [ids+[0]*(max_len-len(ids)) for ids in words_ids]
words_ids_tensor = torch.tensor(words_ids)
words_ids_mask = torch.tensor(words_ids_mask)
self.label_words_ids = nn.Parameter(words_ids_tensor, requires_grad=False)
self.label_words_mask = nn.Parameter(words_ids_mask, requires_grad=False)
[docs] def project(self,
logits: torch.Tensor,
**kwargs,
) -> torch.Tensor:
r"""
Project the labels, the return value is the normalized (sum to 1) probs of label words.
Args:
logits (:obj:`torch.Tensor`): The original logits of label words.
Returns:
:obj:`torch.Tensor`: The normalized logits of label words
"""
label_words_logits = logits[:, self.label_words_ids]
label_words_logits = self.handle_multi_token(label_words_logits, self.label_words_mask)
return label_words_logits
[docs] def process_logits(self, logits: torch.Tensor, **kwargs):
r"""A whole framework to process the original logits over the vocabulary, which contains four steps:
(1) Project the logits into logits of label words
if self.post_log_softmax is True:
(2) Normalize over all label words
(3) Calibrate (optional)
Args:
logits (:obj:`torch.Tensor`): The original logits.
Returns:
(:obj:`torch.Tensor`): The final processed logits over the label words set.
"""
# project
label_words_logits = self.project(logits, **kwargs) #Output: (batch_size, num_classes) or (batch_size, num_classes, num_label_words_per_label)
if self.post_log_softmax:
# normalize
label_words_probs = self.normalize(label_words_logits)
# calibrate
if hasattr(self, "_calibrate_logits") and self._calibrate_logits is not None:
label_words_probs = self.calibrate(label_words_probs=label_words_probs)
# convert to logits
label_words_logits = torch.log(label_words_probs+1e-15)
return label_words_logits
[docs] def normalize(self, logits: torch.Tensor) -> torch.Tensor:
"""
Given logits regarding the entire vocabulary, return the probs over the label words set.
Args:
logits (:obj:`Tensor`): The logits over the entire vocabulary.
Returns:
:obj:`Tensor`: The logits over the label words set.
"""
batch_size = logits.shape[0]
return F.softmax(logits.reshape(batch_size, -1), dim=-1).reshape(*logits.shape)
[docs] def calibrate(self, label_words_probs: torch.Tensor, **kwargs) -> torch.Tensor:
r"""
Args:
label_words_probs (:obj:`torch.Tensor`): The probability distribution of the label words with the shape of [``batch_size``, ``num_classes``, ``num_label_words_per_class``]
Returns:
:obj:`torch.Tensor`: The calibrated probability of label words.
"""
shape = label_words_probs.shape
assert self._calibrate_logits.dim() == 1, "self._calibrate_logits are not 1-d tensor"
calibrate_label_words_probs = self.normalize(self.project(self._calibrate_logits.unsqueeze(0), **kwargs))
assert calibrate_label_words_probs.shape[1:] == label_words_probs.shape[1:] \
and calibrate_label_words_probs.shape[0]==1, "shape not match"
label_words_probs /= (calibrate_label_words_probs+1e-15)
# normalize # TODO Test the performance
norm = label_words_probs.reshape(shape[0], -1).sum(dim=-1,keepdim=True) # TODO Test the performance of detaching()
label_words_probs /= norm
return label_words_probs