# coding=utf-8
# Copyright 2020 The Facebook AI Research Team Authors and 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.
"""PyTorch BART model, ported from the fairseq repo."""
import math
import random
import warnings
from typing import Dict, List, Optional, Tuple
import numpy as np
import torch
import torch.nn.functional as F
from torch import Tensor, nn
from torch.nn import CrossEntropyLoss
from transformers.modeling_bart import *
logger = logging.get_logger(__name__)
_CONFIG_FOR_DOC = "BartConfig"
_TOKENIZER_FOR_DOC = "BartTokenizer"
BART_PRETRAINED_MODEL_ARCHIVE_LIST = [
"facebook/bart-base",
"facebook/bart-large",
"facebook/bart-large-mnli",
"facebook/bart-large-cnn",
"facebook/bart-large-xsum",
"facebook/mbart-large-en-ro",
]
# This list is incomplete. See all BART models at https://huggingface.co/models?filter=bart
BART_START_DOCSTRING = r"""
This model inherits from :class:`~transformers.PreTrainedModel`. Check the superclass documentation for the generic
methods the library implements for all its model (such as downloading or saving, resizing the input embeddings,
pruning heads etc.)
This model is also a PyTorch `torch.nn.Module <https://pytorch.org/docs/stable/nn.html#torch.nn.Module>`__ subclass.
Use it as a regular PyTorch Module and refer to the PyTorch documentation for all matter related to general
usage and behavior.
Parameters:
config (:class:`~transformers.BartConfig`): Model configuration class with all the parameters of the model.
Initializing with a config file does not load the weights associated with the model, only the configuration.
Check out the :meth:`~transformers.PreTrainedModel.from_pretrained` method to load the model weights.
"""
BART_GENERATION_EXAMPLE = r"""
Summarization example::
>>> from transformers import BartTokenizer, BartForConditionalGeneration, BartConfig
>>> # see ``examples/summarization/bart/run_eval.py`` for a longer example
>>> model = BartForConditionalGeneration.from_pretrained('facebook/bart-large-cnn')
>>> tokenizer = BartTokenizer.from_pretrained('facebook/bart-large-cnn')
>>> ARTICLE_TO_SUMMARIZE = "My friends are cool but they eat too many carbs."
>>> inputs = tokenizer([ARTICLE_TO_SUMMARIZE], max_length=1024, return_tensors='pt')
>>> # Generate Summary
>>> summary_ids = model.generate(inputs['input_ids'], num_beams=4, max_length=5, early_stopping=True)
>>> print([tokenizer.decode(g, skip_special_tokens=True, clean_up_tokenization_spaces=False) for g in summary_ids])
"""
BART_INPUTS_DOCSTRING = r"""
Args:
input_ids (:obj:`torch.LongTensor` of shape :obj:`(batch_size, sequence_length)`):
Indices of input sequence tokens in the vocabulary. Padding will be ignored by default should you provide
it.
Indices can be obtained using :class:`~transformers.BartTokenizer`.
See :meth:`transformers.PreTrainedTokenizer.encode` and
:meth:`transformers.PreTrainedTokenizer.__call__` for details.
`What are input IDs? <../glossary.html#input-ids>`__
attention_mask (:obj:`torch.Tensor` of shape :obj:`(batch_size, sequence_length)`, `optional`):
Mask to avoid performing attention on padding token indices.
Mask values selected in ``[0, 1]``:
- 1 for tokens that are **not masked**,
- 0 for tokens that are **masked**.
`What are attention masks? <../glossary.html#attention-mask>`__
decoder_input_ids (:obj:`torch.LongTensor` of shape :obj:`(batch_size, target_sequence_length)`, `optional`):
Provide for translation and summarization training. By default, the model will create this tensor by
shifting the :obj:`input_ids` to the right, following the paper.
decoder_attention_mask (:obj:`torch.BoolTensor` of shape :obj:`(batch_size, tgt_seq_len)`, `optional`):
Default behavior: generate a tensor that ignores pad tokens in :obj:`decoder_input_ids`. Causal mask will
also be used by default.
If you want to change padding behavior, you should read :func:`modeling_bart._prepare_decoder_inputs` and
modify to your needs. See diagram 1 in `the paper <https://arxiv.org/abs/1910.13461>`__ for more
information on the default strategy.
encoder_outputs (:obj:`tuple(tuple(torch.FloatTensor)`, `optional`):
Tuple consists of (:obj:`last_hidden_state`, `optional`: :obj:`hidden_states`, `optional`: :obj:`attentions`)
:obj:`last_hidden_state` of shape :obj:`(batch_size, sequence_length, hidden_size)`, `optional`) is a
sequence of hidden-states at the output of the last layer of the encoder. Used in the cross-attention of
the decoder.
past_key_values (:obj:`tuple(tuple(torch.FloatTensor))` of length :obj:`config.n_layers` with each tuple having 4 tensors of shape :obj:`(batch_size, num_heads, sequence_length - 1, embed_size_per_head)`):
Contains precomputed key and value hidden-states of the attention blocks. Can be used to speed up decoding.
If :obj:`past_key_values` are used, the user can optionally input only the last
``decoder_input_ids`` (those that don't have their past key value states given to this model) of shape
:obj:`(batch_size, 1)` instead of all ``decoder_input_ids`` of shape :obj:`(batch_size, sequence_length)`.
use_cache (:obj:`bool`, `optional`):
If set to :obj:`True`, :obj:`past_key_values` key value states are returned and can be used to speed up
decoding (see :obj:`past_key_values`).
output_attentions (:obj:`bool`, `optional`):
Whether or not to return the attentions tensors of all attention layers. See ``attentions`` under returned
tensors for more detail.
output_hidden_states (:obj:`bool`, `optional`):
Whether or not to return the hidden states of all layers. See ``hidden_states`` under returned tensors for
more detail.
return_dict (:obj:`bool`, `optional`):
Whether or not to return a :class:`~transformers.file_utils.ModelOutput` instead of a plain tuple.
"""
[docs]def invert_mask(attention_mask):
"""Turns 1->0, 0->1, False->True, True-> False"""
# print("attention_mask.shape: ", attention_mask.shape)
assert attention_mask.dim() == 2
return attention_mask.eq(0)
def _prepare_bart_decoder_inputs(
pad_token_id, input_ids, decoder_input_ids=None, decoder_padding_mask=None, causal_mask_dtype=torch.float32
):
"""Prepare masks that ignore padding tokens in the decoder and a causal mask for the decoder if
none are provided. This mimics the default behavior in fairseq. To override it pass in masks.
Note: this is not called during generation
"""
if decoder_input_ids is None:
decoder_input_ids = shift_tokens_right(input_ids, pad_token_id)
bsz, tgt_len = decoder_input_ids.size()
if decoder_padding_mask is None:
decoder_padding_mask = make_padding_mask(decoder_input_ids, pad_token_id)
else:
decoder_padding_mask = invert_mask(decoder_padding_mask)
if decoder_padding_mask is not None and decoder_padding_mask.shape[1] > 1:
# never mask leading token, even if it is pad
decoder_padding_mask[:, 0] = decoder_padding_mask[:, 1]
tmp = fill_with_neg_inf(torch.zeros(tgt_len, tgt_len))
mask = torch.arange(tmp.size(-1))
tmp.masked_fill_(mask < (mask + 1).view(tmp.size(-1), 1), 0)
causal_mask = tmp.to(dtype=causal_mask_dtype, device=decoder_input_ids.device)
return decoder_input_ids, decoder_padding_mask, causal_mask
[docs]class PretrainedBartModel(PreTrainedModel):
config_class = BartConfig
base_model_prefix = "model"
def _init_weights(self, module):
std = self.config.init_std
if isinstance(module, nn.Linear):
module.weight.data.normal_(mean=0.0, std=std)
if module.bias is not None:
module.bias.data.zero_()
elif isinstance(module, SinusoidalPositionalEmbedding):
pass
elif isinstance(module, nn.Embedding):
module.weight.data.normal_(mean=0.0, std=std)
if module.padding_idx is not None:
module.weight.data[module.padding_idx].zero_()
@property
def dummy_inputs(self):
pad_token = self.config.pad_token_id
input_ids = torch.tensor([[0, 6, 10, 4, 2], [0, 8, 12, 2, pad_token]], device=self.device)
dummy_inputs = {
"attention_mask": input_ids.ne(pad_token),
"input_ids": input_ids,
}
return dummy_inputs
def _make_linear_from_emb(emb):
vocab_size, emb_size = emb.weight.shape
lin_layer = nn.Linear(vocab_size, emb_size, bias=False)
lin_layer.weight.data = emb.weight.data
return lin_layer
# Helper Functions, mostly for making masks
def _check_shapes(shape_1, shape2):
if shape_1 != shape2:
raise AssertionError("shape mismatch: {} != {}".format(shape_1, shape2))
[docs]def shift_tokens_right(input_ids, pad_token_id):
"""Shift input ids one token to the right, and wrap the last non pad token (usually <eos>)."""
prev_output_tokens = input_ids.clone()
index_of_eos = (input_ids.ne(pad_token_id).sum(dim=1) - 1).unsqueeze(-1)
prev_output_tokens[:, 0] = input_ids.gather(1, index_of_eos).squeeze()
prev_output_tokens[:, 1:] = input_ids[:, :-1]
return prev_output_tokens
[docs]def make_padding_mask(input_ids, padding_idx=1):
"""True for pad tokens"""
padding_mask = input_ids.eq(padding_idx)
if not padding_mask.any():
padding_mask = None
return padding_mask
# Helper Modules
[docs]class EncoderLayer(nn.Module):
def __init__(self, config: BartConfig):
super().__init__()
self.embed_dim = config.d_model
# self.self_attn = Attention(self.embed_dim, config.encoder_attention_heads, dropout=config.attention_dropout)
# Lilei:
self.self_attn = Attention(self.embed_dim, config.encoder_attention_heads, dropout=config.attention_dropout,
cache_key='encoder', use_prompt=config.use_prompt, preseqlen=config.preseqlen)
self.normalize_before = config.normalize_before
self.self_attn_layer_norm = LayerNorm(self.embed_dim)
self.dropout = config.dropout
self.activation_fn = ACT2FN[config.activation_function]
self.activation_dropout = config.activation_dropout
self.fc1 = nn.Linear(self.embed_dim, config.encoder_ffn_dim)
self.fc2 = nn.Linear(config.encoder_ffn_dim, self.embed_dim)
self.final_layer_norm = LayerNorm(self.embed_dim)
# Lilei:
self.preseqlen = config.preseqlen
self.use_prompt = config.use_prompt
# def forward(self, x, encoder_padding_mask, output_attentions=False):
# Lilei:
[docs] def forward(self, idx, x, encoder_padding_mask, layer_state, output_attentions=False):
"""
Args:
x (Tensor): input to the layer of shape `(seq_len, batch, embed_dim)`
encoder_padding_mask (ByteTensor): binary ByteTensor of shape
`(batch, src_len)` where padding elements are indicated by ``1``.
for t_tgt, t_src is excluded (or masked out), =0 means it is
included in attention
Returns:
encoded output of shape `(seq_len, batch, embed_dim)`
"""
residual = x
if self.normalize_before:
x = self.self_attn_layer_norm(x)
x, attn_weights = self.self_attn(
# query=x, key=x, key_padding_mask=encoder_padding_mask, output_attentions=output_attentions
# Lilei:
idx=idx, query=x, key=x, key_padding_mask=encoder_padding_mask, layer_state=layer_state, output_attentions=output_attentions
)
x = F.dropout(x, p=self.dropout, training=self.training)
x = residual + x
if not self.normalize_before:
x = self.self_attn_layer_norm(x)
residual = x
if self.normalize_before:
x = self.final_layer_norm(x)
x = self.activation_fn(self.fc1(x))
x = F.dropout(x, p=self.activation_dropout, training=self.training)
x = self.fc2(x)
x = F.dropout(x, p=self.dropout, training=self.training)
x = residual + x
if not self.normalize_before:
x = self.final_layer_norm(x)
# Lilei:
# if torch.isinf(x).any() or torch.isnan(x).any():
# clamp_value = torch.finfo(x.dtype).max - 1000
# x = torch.clamp(x, min=-clamp_value, max=clamp_value)
return x, attn_weights
[docs]class BartEncoder(nn.Module):
"""
Transformer encoder consisting of *config.encoder_layers* self attention layers. Each layer
is a :class:`EncoderLayer`.
Args:
config: BartConfig
"""
def __init__(self, config: BartConfig, embed_tokens):
super().__init__()
self.dropout = config.dropout
self.layerdrop = config.encoder_layerdrop
embed_dim = embed_tokens.embedding_dim
self.embed_scale = math.sqrt(embed_dim) if config.scale_embedding else 1.0
self.padding_idx = embed_tokens.padding_idx
self.max_source_positions = config.max_position_embeddings
self.embed_tokens = embed_tokens
if config.static_position_embeddings:
self.embed_positions = SinusoidalPositionalEmbedding(
config.max_position_embeddings, embed_dim, self.padding_idx
)
else:
self.embed_positions = LearnedPositionalEmbedding(
config.max_position_embeddings,
embed_dim,
self.padding_idx,
config.extra_pos_embeddings,
)
self.layers = nn.ModuleList([EncoderLayer(config) for _ in range(config.encoder_layers)])
self.layernorm_embedding = LayerNorm(embed_dim) if config.normalize_embedding else nn.Identity()
# mbart has one extra layer_norm
self.layer_norm = LayerNorm(config.d_model) if config.add_final_layer_norm else None
[docs] def forward(
# self, input_ids, attention_mask=None, output_attentions=False, output_hidden_states=False, return_dict=False
# Lilei:
self, input_ids, attention_mask=None, past_key_values=None,
output_attentions=False, output_hidden_states=False, return_dict=False
):
"""
Args:
input_ids (LongTensor): tokens in the source language of shape
`(batch, src_len)`
attention_mask (torch.LongTensor): indicating which indices are padding tokens.
Returns:
BaseModelOutput or Tuple comprised of:
- **x** (Tensor): the last encoder layer's output of
shape `(src_len, batch, embed_dim)`
- **encoder_states** (tuple(torch.FloatTensor)): all intermediate
hidden states of shape `(src_len, batch, embed_dim)`.
Only populated if *output_hidden_states:* is True.
- **all_attentions** (tuple(torch.FloatTensor)): Attention weights for each layer.
During training might not be of length n_layers because of layer dropout.
"""
# check attention mask and invert
if attention_mask is not None:
# print("encoder attention_mask.shape: ", attention_mask.shape)
attention_mask = invert_mask(attention_mask)
inputs_embeds = self.embed_tokens(input_ids) * self.embed_scale
embed_pos = self.embed_positions(input_ids)
x = inputs_embeds + embed_pos
x = self.layernorm_embedding(x)
x = F.dropout(x, p=self.dropout, training=self.training)
# B x T x C -> T x B x C
x = x.transpose(0, 1)
encoder_states = [] if output_hidden_states else None
all_attentions = () if output_attentions else None
# LiLei
for idx, encoder_layer in enumerate(self.layers):
if output_hidden_states:
encoder_states.append(x)
# add LayerDrop (see https://arxiv.org/abs/1909.11556 for description)
dropout_probability = random.uniform(0, 1)
if self.training and (dropout_probability < self.layerdrop): # skip the layer
attn = None
else:
layer_state = past_key_values[idx] if past_key_values is not None else None
x, attn = encoder_layer(idx, x, attention_mask, layer_state, output_attentions=output_attentions)
if output_attentions:
all_attentions = all_attentions + (attn,)
if self.layer_norm:
x = self.layer_norm(x)
if output_hidden_states:
encoder_states.append(x)
# T x B x C -> B x T x C
encoder_states = tuple(hidden_state.transpose(0, 1) for hidden_state in encoder_states)
# T x B x C -> B x T x C
x = x.transpose(0, 1)
if not return_dict:
return tuple(v for v in [x, encoder_states, all_attentions] if v is not None)
return BaseModelOutput(last_hidden_state=x, hidden_states=encoder_states, attentions=all_attentions)
# LiLei: append
[docs] def forward_with_encoder_past(
self, input_ids, attention_mask=None, past_key_values=None,
output_attentions=False, output_hidden_states=False, return_dict=False
):
"""
Args:
input_ids (LongTensor): tokens in the source language of shape
`(batch, src_len)`
attention_mask (torch.LongTensor): indicating which indices are padding tokens.
Returns:
BaseModelOutput or Tuple comprised of:
- **x** (Tensor): the last encoder layer's output of
shape `(src_len, batch, embed_dim)`
- **encoder_states** (tuple(torch.FloatTensor)): all intermediate
hidden states of shape `(src_len, batch, embed_dim)`.
Only populated if *output_hidden_states:* is True.
- **all_attentions** (tuple(torch.FloatTensor)): Attention weights for each layer.
During training might not be of length n_layers because of layer dropout.
"""
# check attention mask and invert
if attention_mask is not None:
attention_mask = invert_mask(attention_mask)
inputs_embeds = self.embed_tokens(input_ids) * self.embed_scale
embed_pos = self.embed_positions(input_ids)
x = inputs_embeds + embed_pos
x = self.layernorm_embedding(x)
x = F.dropout(x, p=self.dropout, training=self.training)
# B x T x C -> T x B x C
x = x.transpose(0, 1)
encoder_states = [] if output_hidden_states else None
all_attentions = () if output_attentions else None
encoder_cache = []
for idx, encoder_layer in enumerate(self.layers):
if output_hidden_states:
encoder_states.append(x)
# add LayerDrop (see https://arxiv.org/abs/1909.11556 for description)
dropout_probability = random.uniform(0, 1)
if self.training and (dropout_probability < self.layerdrop): # skip the layer
attn = None
else:
layer_state = past_key_values[idx] if past_key_values is not None else {}
x, attn = encoder_layer(idx, x, attention_mask, layer_state, output_attentions=output_attentions)
# print('new layer state', layer_state)
if output_attentions:
all_attentions = all_attentions + (attn,)
# URGENT
encoder_cache.append(layer_state.copy())
if self.layer_norm:
x = self.layer_norm(x)
if output_hidden_states:
encoder_states.append(x)
# T x B x C -> B x T x C
encoder_states = tuple(hidden_state.transpose(0, 1) for hidden_state in encoder_states)
# T x B x C -> B x T x C
x = x.transpose(0, 1)
return BaseModelOutputWithPast(last_hidden_state=x, hidden_states=encoder_states,
attentions=all_attentions, past_key_values=encoder_cache)
[docs]class DecoderLayer(nn.Module):
def __init__(self, config: BartConfig):
super().__init__()
self.embed_dim = config.d_model
self.self_attn = Attention(
embed_dim=self.embed_dim,
num_heads=config.decoder_attention_heads,
dropout=config.attention_dropout,
# LiLEi:
cache_key='self',
use_prompt=config.use_prompt,
preseqlen=config.preseqlen,
)
self.dropout = config.dropout
self.activation_fn = ACT2FN[config.activation_function]
self.activation_dropout = config.activation_dropout
self.normalize_before = config.normalize_before
self.self_attn_layer_norm = LayerNorm(self.embed_dim)
self.encoder_attn = Attention(
self.embed_dim,
config.decoder_attention_heads,
dropout=config.attention_dropout,
# LiLei:
cache_key='encoder_decoder',
encoder_decoder_attention=True,
use_prompt=config.use_prompt,
preseqlen=config.preseqlen,
)
self.encoder_attn_layer_norm = LayerNorm(self.embed_dim)
self.fc1 = nn.Linear(self.embed_dim, config.decoder_ffn_dim)
self.fc2 = nn.Linear(config.decoder_ffn_dim, self.embed_dim)
self.final_layer_norm = LayerNorm(self.embed_dim)
[docs] def forward(
self,
idx, ###
x,
encoder_hidden_states,
encoder_attn_mask=None,
layer_state=None,
causal_mask=None,
decoder_padding_mask=None,
output_attentions=False,
):
residual = x
if layer_state is None:
layer_state = {}
if self.normalize_before:
x = self.self_attn_layer_norm(x)
# Self Attention
x, self_attn_weights = self.self_attn(
idx=idx, ###
query=x,
key=x,
layer_state=layer_state, # adds keys to layer state
key_padding_mask=decoder_padding_mask,
attn_mask=causal_mask,
output_attentions=output_attentions,
)
x = F.dropout(x, p=self.dropout, training=self.training)
x = residual + x
if not self.normalize_before:
x = self.self_attn_layer_norm(x)
# Cross attention
residual = x
assert self.encoder_attn.cache_key != self.self_attn.cache_key
if self.normalize_before:
x = self.encoder_attn_layer_norm(x)
x, _ = self.encoder_attn(
idx=idx, ###
query=x,
key=encoder_hidden_states,
key_padding_mask=encoder_attn_mask,
layer_state=layer_state, # mutates layer state
)
x = F.dropout(x, p=self.dropout, training=self.training)
x = residual + x
if not self.normalize_before:
x = self.encoder_attn_layer_norm(x)
# Fully Connected
residual = x
if self.normalize_before:
x = self.final_layer_norm(x)
x = self.activation_fn(self.fc1(x))
x = F.dropout(x, p=self.activation_dropout, training=self.training)
x = self.fc2(x)
x = F.dropout(x, p=self.dropout, training=self.training)
x = residual + x
if not self.normalize_before:
x = self.final_layer_norm(x)
return (
x,
self_attn_weights,
layer_state,
) # just self_attn weights for now, following t5, layer_state = cache for decoding
[docs]class BartDecoder(nn.Module):
"""
Transformer decoder consisting of *config.decoder_layers* layers. Each layer
is a :class:`DecoderLayer`.
Args:
config: BartConfig
embed_tokens (torch.nn.Embedding): output embedding
"""
def __init__(self, config: BartConfig, embed_tokens: nn.Embedding):
super().__init__()
self.dropout = config.dropout
self.layerdrop = config.decoder_layerdrop
# self.do_blenderbot_90_layernorm = config.do_blenderbot_90_layernorm # layernorm variant
self.padding_idx = embed_tokens.padding_idx
self.max_target_positions = config.max_position_embeddings
self.embed_scale = math.sqrt(config.d_model) if config.scale_embedding else 1.0
self.embed_tokens = embed_tokens
if config.static_position_embeddings:
self.embed_positions = SinusoidalPositionalEmbedding(
config.max_position_embeddings, config.d_model, config.pad_token_id
)
else:
self.embed_positions = LearnedPositionalEmbedding(
config.max_position_embeddings,
config.d_model,
self.padding_idx,
config.extra_pos_embeddings
)
self.layers = nn.ModuleList(
[DecoderLayer(config) for _ in range(config.decoder_layers)]
) # type: List[DecoderLayer]
self.layernorm_embedding = LayerNorm(config.d_model) if config.normalize_embedding else nn.Identity()
self.layer_norm = LayerNorm(config.d_model) if config.add_final_layer_norm else None
# self.config = config
[docs] def forward(
self,
input_ids,
encoder_hidden_states,
encoder_padding_mask,
decoder_padding_mask,
decoder_causal_mask,
past_key_values=None,
use_cache=False,
# LILEI:
use_prompt=False,
output_attentions=False,
output_hidden_states=False,
return_dict=False,
**unused,
):
"""
Includes several features from "Jointly Learning to Align and
Translate with Transformer Models" (Garg et al., EMNLP 2019).
Args:
input_ids (LongTensor): previous decoder outputs of shape
`(batch, tgt_len)`, for teacher forcing
encoder_hidden_states: output from the encoder, used for
encoder-side attention
encoder_padding_mask: for ignoring pad tokens
past_key_values (dict or None): dictionary used for storing state during generation
Returns:
BaseModelOutputWithPast or tuple:
- the decoder's features of shape `(batch, tgt_len, embed_dim)`
- the cache
- hidden states
- attentions
"""
if "decoder_cached_states" in unused:
warnings.warn(
"The `decoder_cached_states` argument is deprecated and will be removed in a future version, use `past_key_values` instead.",
FutureWarning,
)
past_key_values = unused.pop("decoder_cached_states")
if "decoder_past_key_values" in unused:
warnings.warn(
"The `decoder_past_key_values` argument is deprecated and will be removed in a future version, use `past_key_values` instead.",
FutureWarning,
)
past_key_values = unused.pop("decoder_past_key_values")
# check attention mask and invert
if encoder_padding_mask is not None:
encoder_padding_mask = invert_mask(encoder_padding_mask)
# embed positions
positions = self.embed_positions(input_ids, use_cache=use_cache)
if use_cache:
input_ids = input_ids[:, -1:]
positions = positions[:, -1:]
x = self.embed_tokens(input_ids) * self.embed_scale
# LILEI:
# if self.do_blenderbot_90_layernorm:
# x = self.layernorm_embedding(x)
# x += positions
# else:
# x += positions
# x = self.layernorm_embedding(x)
x += positions
x = self.layernorm_embedding(x)
x = F.dropout(x, p=self.dropout, training=self.training)
# Convert to Bart output format: (seq_len, BS, model_dim) -> (BS, seq_len, model_dim)
x = x.transpose(0, 1)
encoder_hidden_states = encoder_hidden_states.transpose(0, 1)
# decoder layers
all_hidden_states = () if output_hidden_states else None
all_self_attns = () if output_attentions else None
next_decoder_cache = []
for idx, decoder_layer in enumerate(self.layers):
# add LayerDrop (see https://arxiv.org/abs/1909.11556 for description)
if output_hidden_states:
all_hidden_states += (x,)
dropout_probability = random.uniform(0, 1)
if self.training and (dropout_probability < self.layerdrop):
continue
layer_state = past_key_values[idx] if past_key_values is not None else None
x, layer_self_attn, layer_past = decoder_layer(
idx, ###
x,
encoder_hidden_states,
encoder_attn_mask=encoder_padding_mask,
decoder_padding_mask=decoder_padding_mask,
layer_state=layer_state,
causal_mask=decoder_causal_mask,
output_attentions=output_attentions,
)
if use_cache:
next_decoder_cache.append(layer_past.copy())
if output_attentions:
all_self_attns += (layer_self_attn,)
if self.layer_norm: # if config.add_final_layer_norm (mBART)
x = self.layer_norm(x)
# Convert to standard output format: (seq_len, BS, model_dim) -> (BS, seq_len, model_dim)
if output_hidden_states:
all_hidden_states = tuple(hidden_state.transpose(0, 1) for hidden_state in all_hidden_states)
x = x.transpose(0, 1)
encoder_hidden_states = encoder_hidden_states.transpose(0, 1)
next_cache = next_decoder_cache if use_cache else None
if not return_dict:
return tuple(v for v in [x, next_cache, all_hidden_states, all_self_attns] if v is not None)
return BaseModelOutputWithPast(
last_hidden_state=x, past_key_values=next_cache, hidden_states=all_hidden_states, attentions=all_self_attns
)
def _reorder_buffer(attn_cache, new_order):
for k, input_buffer_k in attn_cache.items():
if input_buffer_k is not None:
attn_cache[k] = input_buffer_k.index_select(0, new_order)
return attn_cache
[docs]class Attention(nn.Module):
"""Multi-headed attention from 'Attention Is All You Need' paper"""
def __init__(
self,
embed_dim,
num_heads,
dropout=0.0,
bias=True,
encoder_decoder_attention=False, # otherwise self_attention
# LILEI
cache_key=None,
preseqlen=-1,
use_prompt=True
):
super().__init__()
self.embed_dim = embed_dim
self.num_heads = num_heads
self.dropout = dropout
self.head_dim = embed_dim // num_heads
assert self.head_dim * num_heads == self.embed_dim, "embed_dim must be divisible by num_heads"
self.scaling = self.head_dim ** -0.5
self.encoder_decoder_attention = encoder_decoder_attention
self.k_proj = nn.Linear(embed_dim, embed_dim, bias=bias)
self.v_proj = nn.Linear(embed_dim, embed_dim, bias=bias)
self.q_proj = nn.Linear(embed_dim, embed_dim, bias=bias)
self.out_proj = nn.Linear(embed_dim, embed_dim, bias=bias)
# self.cache_key = "encoder_decoder" if self.encoder_decoder_attention else "self"
# LILEI
assert cache_key in ['self', 'encoder_decoder', 'encoder']
if self.encoder_decoder_attention:
assert cache_key == 'encoder_decoder'
self.cache_key = cache_key
self.use_prompt=use_prompt
self.preseqlen = preseqlen
def _shape(self, tensor, seq_len, bsz):
return tensor.contiguous().view(seq_len, bsz * self.num_heads, self.head_dim).transpose(0, 1)
[docs] def forward(
self,
idx, ###
query,
key: Optional[Tensor],
key_padding_mask: Optional[Tensor] = None,
layer_state: Optional[Dict[str, Optional[Tensor]]] = None,
attn_mask: Optional[Tensor] = None,
output_attentions=False,
) -> Tuple[Tensor, Optional[Tensor]]:
"""Input shape: Time(SeqLen) x Batch x Channel"""
static_kv: bool = self.encoder_decoder_attention
tgt_len, bsz, embed_dim = query.size()
assert embed_dim == self.embed_dim
assert list(query.size()) == [tgt_len, bsz, embed_dim]
# get here for encoder decoder cause of static_kv
# LILEI
no_extend = False
if layer_state is not None: # reuse k,v and encoder_padding_mask
saved_state = layer_state.get(self.cache_key, {})
# if "prev_key" in saved_state and static_kv:
# # previous time steps are cached - no need to recompute key and value if they are static
# key = None
# LILEI
use_prompt = self.use_prompt
preseqlen = self.preseqlen
if "prev_key" in saved_state and static_kv and use_prompt: # generation time AND compute cross attention.
computed_len = saved_state['prev_key'].size(2)
# print(computed_len)
if computed_len > preseqlen:
# print('Happen for generation, NOT for training.')
key=None
no_extend = True
elif "prev_key" in saved_state and static_kv and not use_prompt:
key = None
no_extend = True
else:
saved_state = None
layer_state = {}
q = self.q_proj(query) * self.scaling
if static_kv:
if key is None:
k = v = None
else:
k = self.k_proj(key)
v = self.v_proj(key)
else:
k = self.k_proj(query)
v = self.v_proj(query)
q = self._shape(q, tgt_len, bsz)
if k is not None:
k = self._shape(k, -1, bsz)
if v is not None:
v = self._shape(v, -1, bsz)
if saved_state is not None:
# k, v, key_padding_mask = self._use_saved_state(k, v, saved_state, key_padding_mask, static_kv, bsz)
k, v, key_padding_mask = self._use_saved_state(k, v, saved_state, key_padding_mask, no_extend, bsz)
# # Update cache
# layer_state[self.cache_key] = {
# "prev_key": k.view(bsz, self.num_heads, -1, self.head_dim),
# "prev_value": v.view(bsz, self.num_heads, -1, self.head_dim),
# "prev_key_padding_mask": key_padding_mask if not static_kv else None,
# }
# LILEI
# Update cache
layer_state[self.cache_key] = {
"prev_key": k.view(bsz, self.num_heads, -1, self.head_dim),
"prev_value": v.view(bsz, self.num_heads, -1, self.head_dim),
# "prev_key_padding_mask": key_padding_mask if not static_kv else None,
"prev_key_padding_mask": key_padding_mask,
}
assert k is not None
src_len = k.size(1)
attn_weights = torch.bmm(q, k.transpose(1, 2))
assert attn_weights.size() == (bsz * self.num_heads, tgt_len, src_len)
if attn_mask is not None:
attn_weights = attn_weights.view(bsz, self.num_heads, tgt_len, src_len) + attn_mask
attn_weights = attn_weights.view(bsz * self.num_heads, tgt_len, src_len)
# This is part of a workaround to get around fork/join parallelism not supporting Optional types.
if key_padding_mask is not None and key_padding_mask.dim() == 0:
key_padding_mask = None
assert key_padding_mask is None or key_padding_mask.size()[:2] == (
bsz,
src_len,
)
if key_padding_mask is not None: # don't attend to padding symbols
attn_weights = attn_weights.view(bsz, self.num_heads, tgt_len, src_len)
reshaped = key_padding_mask.unsqueeze(1).unsqueeze(2)
attn_weights = attn_weights.masked_fill(reshaped, float("-inf"))
attn_weights = attn_weights.view(bsz * self.num_heads, tgt_len, src_len)
attn_weights = F.softmax(attn_weights, dim=-1)
attn_probs = F.dropout(
attn_weights,
p=self.dropout,
training=self.training,
)
assert v is not None
attn_output = torch.bmm(attn_probs, v)
assert attn_output.size() == (bsz * self.num_heads, tgt_len, self.head_dim)
attn_output = attn_output.transpose(0, 1).contiguous().view(tgt_len, bsz, embed_dim)
attn_output = self.out_proj(attn_output)
if output_attentions:
attn_weights = attn_weights.view(bsz, self.num_heads, tgt_len, src_len)
else:
attn_weights = None
return attn_output, attn_weights
def _use_saved_state(self, k, v, saved_state, key_padding_mask, static_kv, bsz):
# saved states are stored with shape (bsz, num_heads, seq_len, head_dim)
if "prev_key" in saved_state:
_prev_key = saved_state["prev_key"]
assert _prev_key is not None
# print(_prev_key.shape)
# print(bsz, self.num_heads, self.head_dim, bsz* self.num_heads)
prev_key = _prev_key.view(bsz * self.num_heads, -1, self.head_dim)
if static_kv:
k = prev_key
else:
assert k is not None
k = torch.cat([prev_key, k], dim=1)
if "prev_value" in saved_state:
_prev_value = saved_state["prev_value"]
assert _prev_value is not None
prev_value = _prev_value.view(bsz * self.num_heads, -1, self.head_dim)
if static_kv:
v = prev_value
else:
assert v is not None
v = torch.cat([prev_value, v], dim=1)
assert k is not None and v is not None
prev_key_padding_mask: Optional[Tensor] = saved_state.get("prev_key_padding_mask", None)
if prev_key_padding_mask is not None:
# print('using this prev key_padding',prev_key_padding_mask.shape)
if static_kv:
new_key_padding_mask = prev_key_padding_mask
else:
# print(key_padding_mask.shape if key_padding_mask is not None else None )
# print(prev_key_padding_mask.shape if prev_key_padding_mask is not None else None)
if key_padding_mask is not None:
new_key_padding_mask = torch.cat([prev_key_padding_mask, key_padding_mask], dim=1)
else:
new_key_padding_mask = None
else:
new_key_padding_mask = key_padding_mask
return k, v, new_key_padding_mask
[docs]class BartClassificationHead(nn.Module):
"""Head for sentence-level classification tasks."""
# This can trivially be shared with RobertaClassificationHead
def __init__(
self,
input_dim,
inner_dim,
num_classes,
pooler_dropout,
):
super().__init__()
self.dense = nn.Linear(input_dim, inner_dim)
self.dropout = nn.Dropout(p=pooler_dropout)
self.out_proj = nn.Linear(inner_dim, num_classes)
[docs] def forward(self, x):
x = self.dropout(x)
x = self.dense(x)
x = torch.tanh(x)
x = self.dropout(x)
x = self.out_proj(x)
return x
[docs]class LearnedPositionalEmbedding(nn.Embedding):
"""
This module learns positional embeddings up to a fixed maximum size.
Padding ids are ignored by either offsetting based on padding_idx
or by setting padding_idx to None and ensuring that the appropriate
position ids are passed to the forward function.
"""
def __init__(self, num_embeddings: int, embedding_dim: int, padding_idx: int, offset):
# Bart is set up so that if padding_idx is specified then offset the embedding ids by 2
# and adjust num_embeddings appropriately. Other models dont have this hack
self.offset = offset
assert padding_idx is not None
num_embeddings += offset
super().__init__(num_embeddings, embedding_dim, padding_idx=padding_idx)
[docs] def forward(self, input_ids, use_cache=False):
"""Input is expected to be of size [bsz x seqlen]."""
bsz, seq_len = input_ids.shape[:2]
if use_cache:
positions = input_ids.data.new(1, 1).fill_(seq_len - 1) # called before slicing
else:
# starts at 0, ends at 1-seq_len
positions = torch.arange(seq_len, dtype=torch.long, device=self.weight.device)
return super().forward(positions + self.offset)
[docs]def LayerNorm(normalized_shape, eps=1e-5, elementwise_affine=True):
if torch.cuda.is_available():
try:
from apex.normalization import FusedLayerNorm
return FusedLayerNorm(normalized_shape, eps, elementwise_affine)
except ImportError:
pass
return torch.nn.LayerNorm(normalized_shape, eps, elementwise_affine)
[docs]def fill_with_neg_inf(t):
"""FP16-compatible function that fills a input_ids with -inf."""
return t.float().fill_(float("-inf")).type_as(t)
# Public API
def _get_shape(t):
return getattr(t, "shape", None)
[docs]@add_start_docstrings(
"The bare BART Model outputting raw hidden-states without any specific head on top.",
BART_START_DOCSTRING,
)
class BartModel(PretrainedBartModel):
def __init__(self, config: BartConfig):
super().__init__(config)
padding_idx, vocab_size = config.pad_token_id, config.vocab_size
self.shared = nn.Embedding(vocab_size, config.d_model, padding_idx)
self.encoder = BartEncoder(config, self.shared)
self.decoder = BartDecoder(config, self.shared)
self.init_weights()
[docs] @add_start_docstrings_to_callable(BART_INPUTS_DOCSTRING)
@add_code_sample_docstrings(
tokenizer_class=_TOKENIZER_FOR_DOC,
checkpoint="facebook/bart-large",
output_type=Seq2SeqModelOutput,
config_class=_CONFIG_FOR_DOC,
)
def forward(
self,
input_ids,
attention_mask=None,
decoder_input_ids=None,
encoder_outputs: Optional[Tuple] = None,
decoder_attention_mask=None,
past_key_values=None,
use_cache=None,
# LILEI
use_prompt=None,
output_attentions=None,
output_hidden_states=None,
return_dict=None,
**kwargs,
):
if "decoder_past_key_values" in kwargs:
warnings.warn(
"The `decoder_past_key_values` argument is deprecated and will be removed in a future version, use `past_key_values` instead.",
FutureWarning,
)
past_key_values = kwargs.pop("decoder_past_key_values")
if decoder_input_ids is None:
use_cache = False
output_attentions = output_attentions if output_attentions is not None else self.config.output_attentions
output_hidden_states = (
output_hidden_states if output_hidden_states is not None else self.config.output_hidden_states
)
use_cache = use_cache if use_cache is not None else self.config.use_cache
return_dict = return_dict if return_dict is not None else self.config.use_return_dict
# # make masks if user doesn't supply
# if not use_cache:
# decoder_input_ids, decoder_padding_mask, causal_mask = _prepare_bart_decoder_inputs(
# self.config,
# input_ids,
# decoder_input_ids=decoder_input_ids,
# decoder_padding_mask=decoder_attention_mask,
# causal_mask_dtype=self.shared.weight.dtype,
# )
# else:
# decoder_padding_mask, causal_mask = None, None
# LILEI causal_mask
if not use_cache:
print('not use cache')
decoder_input_ids, decoder_padding_mask, causal_mask = _prepare_bart_decoder_inputs(
self.config,
input_ids,
decoder_input_ids=decoder_input_ids,
decoder_padding_mask=decoder_attention_mask,
causal_mask_dtype=self.shared.weight.dtype,
)
if use_prompt:
bsz, _, seqlen, _ = past_key_values[0]['self']['prev_value'].shape
tgt_len = decoder_input_ids.size(1)
temp_mask = torch.zeros(tgt_len, seqlen).to(causal_mask.device) #tgtlen, preseqlen
causal_mask = torch.cat([temp_mask, causal_mask],dim=1) #tgtlen, preseqlen+tgtlen
else:
print('USE cache')
decoder_padding_mask, causal_mask = None, None
assert decoder_input_ids is not None
if encoder_outputs is None:
encoder_outputs = self.encoder(
input_ids=input_ids,
attention_mask=attention_mask,
# LILEI
past_key_values=past_key_values,
output_attentions=output_attentions,
output_hidden_states=output_hidden_states,
return_dict=return_dict,
)
# If the user passed a tuple for encoder_outputs, we wrap it in a BaseModelOuput when return_dict=False
elif return_dict and not isinstance(encoder_outputs, BaseModelOutput):
encoder_outputs = BaseModelOutput(
last_hidden_state=encoder_outputs[0],
hidden_states=encoder_outputs[1] if len(encoder_outputs) > 1 else None,
attentions=encoder_outputs[2] if len(encoder_outputs) > 2 else None,
)
# decoder outputs consists of (dec_features, layer_state, dec_hidden, dec_attn)
decoder_outputs = self.decoder(
decoder_input_ids,
encoder_outputs[0],
attention_mask,
decoder_padding_mask,
decoder_causal_mask=causal_mask,
past_key_values=past_key_values,
use_cache=use_cache,
output_attentions=output_attentions,
output_hidden_states=output_hidden_states,
return_dict=return_dict,
)
if not return_dict:
return decoder_outputs + encoder_outputs
return Seq2SeqModelOutput(
last_hidden_state=decoder_outputs.last_hidden_state,
past_key_values=decoder_outputs.past_key_values,
decoder_hidden_states=decoder_outputs.hidden_states,
decoder_attentions=decoder_outputs.attentions,
encoder_last_hidden_state=encoder_outputs.last_hidden_state,
encoder_hidden_states=encoder_outputs.hidden_states,
encoder_attentions=encoder_outputs.attentions,
)
[docs] def get_output_embeddings(self):
return _make_linear_from_emb(self.shared) # make it on the fly
[docs]@add_start_docstrings(
"The BART Model with a language modeling head. Can be used for summarization.", BART_START_DOCSTRING
)
class BartForConditionalGeneration(PretrainedBartModel):
base_model_prefix = "model"
authorized_missing_keys = [r"final_logits_bias", r"encoder\.version", r"decoder\.version"]
def __init__(self, config: BartConfig):
super().__init__(config)
# LILEI
print('Init the BartForConditionalGeneration Model with config.use_prompt={}, '
'config.preseqlen={}'.format(config.use_prompt, config.preseqlen))
base_model = BartModel(config)
self.model = base_model
self.register_buffer("final_logits_bias", torch.zeros((1, self.model.shared.num_embeddings)))
[docs] def resize_token_embeddings(self, new_num_tokens: int) -> nn.Embedding:
old_num_tokens = self.model.shared.num_embeddings
new_embeddings = super().resize_token_embeddings(new_num_tokens)
self.model.shared = new_embeddings
self._resize_final_logits_bias(new_num_tokens, old_num_tokens)
return new_embeddings
def _resize_final_logits_bias(self, new_num_tokens: int, old_num_tokens: int) -> None:
if new_num_tokens <= old_num_tokens:
new_bias = self.final_logits_bias[:, :new_num_tokens]
else:
extra_bias = torch.zeros((1, new_num_tokens - old_num_tokens), device=self.final_logits_bias.device)
new_bias = torch.cat([self.final_logits_bias, extra_bias], dim=1)
self.register_buffer("final_logits_bias", new_bias)
[docs] @add_start_docstrings_to_callable(BART_INPUTS_DOCSTRING)
@replace_return_docstrings(output_type=Seq2SeqLMOutput, config_class=_CONFIG_FOR_DOC)
@add_end_docstrings(BART_GENERATION_EXAMPLE)
def forward(
self,
input_ids,
attention_mask=None,
encoder_outputs=None,
decoder_input_ids=None,
decoder_attention_mask=None,
past_key_values=None,
labels=None,
use_cache=None,
# LILEI
use_prompt=None,
output_attentions=None,
output_hidden_states=None,
return_dict=None,
**unused,
):
r"""
labels (:obj:`torch.LongTensor` of shape :obj:`(batch_size, sequence_length)`, `optional`):
Labels for computing the masked language modeling loss.
Indices should either be in ``[0, ..., config.vocab_size]`` or -100 (see ``input_ids`` docstring).
Tokens with indices set to ``-100`` are ignored (masked), the loss is only computed for the tokens
with labels in ``[0, ..., config.vocab_size]``.
Returns:
Conditional generation example::
>>> # Mask filling only works for bart-large
>>> from transformers import BartTokenizer, BartForConditionalGeneration
>>> tokenizer = BartTokenizer.from_pretrained('facebook/bart-large')
>>> TXT = "My friends are <mask> but they eat too many carbs."
>>> model = BartForConditionalGeneration.from_pretrained('facebook/bart-large')
>>> input_ids = tokenizer([TXT], return_tensors='pt')['input_ids']
>>> logits = model(input_ids).logits
>>> masked_index = (input_ids[0] == tokenizer.mask_token_id).nonzero().item()
>>> probs = logits[0, masked_index].softmax(dim=0)
>>> values, predictions = probs.topk(5)
>>> tokenizer.decode(predictions).split()
>>> # ['good', 'great', 'all', 'really', 'very']
"""
if "lm_labels" in unused:
warnings.warn(
"The `lm_labels` argument is deprecated and will be removed in a future version, use `labels` instead.",
FutureWarning,
)
labels = unused.pop("lm_labels")
if "decoder_cached_states" in unused:
warnings.warn(
"The `decoder_cached_states` argument is deprecated and will be removed in a future version, use `past_key_values` instead.",
FutureWarning,
)
past_key_values = unused.pop("decoder_cached_states")
if "decoder_past_key_values" in unused:
warnings.warn(
"The `decoder_past_key_values` argument is deprecated and will be removed in a future version, use `past_key_values` instead.",
FutureWarning,
)
past_key_values = unused.pop("decoder_past_key_values")
return_dict = return_dict if return_dict is not None else self.config.use_return_dict
if labels is not None:
use_cache = False
if decoder_input_ids is None:
decoder_input_ids = shift_tokens_right(labels, self.config.pad_token_id)
outputs = self.model(
input_ids,
attention_mask=attention_mask,
decoder_input_ids=decoder_input_ids,
encoder_outputs=encoder_outputs,
decoder_attention_mask=decoder_attention_mask,
past_key_values=past_key_values,
use_cache=use_cache,
use_prompt=use_prompt,
output_attentions=output_attentions,
output_hidden_states=output_hidden_states,
return_dict=return_dict,
)
lm_logits = F.linear(outputs[0], self.model.shared.weight, bias=self.final_logits_bias)
masked_lm_loss = None
if labels is not None:
loss_fct = CrossEntropyLoss()
# TODO(SS): do we need to ignore pad tokens in labels?
masked_lm_loss = loss_fct(lm_logits.view(-1, self.config.vocab_size), labels.view(-1))
if not return_dict:
output = (lm_logits,) + outputs[1:]
return ((masked_lm_loss,) + output) if masked_lm_loss is not None else output
return Seq2SeqLMOutput(
loss=masked_lm_loss,
logits=lm_logits,
past_key_values=outputs.past_key_values,
decoder_hidden_states=outputs.decoder_hidden_states,
decoder_attentions=outputs.decoder_attentions,
encoder_last_hidden_state=outputs.encoder_last_hidden_state,
encoder_hidden_states=outputs.encoder_hidden_states,
encoder_attentions=outputs.encoder_attentions,
)
[docs] def adjust_logits_during_generation(self, logits, cur_len, max_length):
if cur_len == 1 and self.config.force_bos_token_to_be_generated:
self._force_token_ids_generation(logits, self.config.bos_token_id)
elif cur_len == max_length - 1 and self.config.eos_token_id is not None:
self._force_token_ids_generation(logits, self.config.eos_token_id)
return logits
def _force_token_ids_generation(self, scores, token_id) -> None:
"""force one of token_ids to be generated by setting prob of all other tokens to 0 (logprob=-float("inf"))"""
scores[:, [x for x in range(self.config.vocab_size) if x != token_id]] = -float("inf")
@staticmethod
def _reorder_cache(past, beam_idx):
reordered_past = []
for layer_past in past:
# get the correct batch idx from decoder layer's batch dim for cross and self-attn
layer_past_new = {
# attn_key: _reorder_buffer(attn_cache, beam_idx) for attn_key, attn_cache in layer_past.items()
attn_key: _reorder_buffer(attn_cache, beam_idx) for attn_key, attn_cache in layer_past.items() if attn_key in ['encoder_decoder', 'self']
}
reordered_past.append(layer_past_new)
return reordered_past
[docs] def get_encoder(self):
return self.model.encoder
[docs] def get_output_embeddings(self):
return _make_linear_from_emb(self.model.shared) # make it on the fly
[docs]@add_start_docstrings(
"""Bart model with a sequence classification/head on top (a linear layer on top of the pooled output) e.g. for GLUE tasks. """,
BART_START_DOCSTRING,
)
class BartForSequenceClassification(PretrainedBartModel):
def __init__(self, config: BartConfig, **kwargs):
super().__init__(config, **kwargs)
self.model = BartModel(config)
self.classification_head = BartClassificationHead(
config.d_model,
config.d_model,
config.num_labels,
config.classifier_dropout,
)
self.model._init_weights(self.classification_head.dense)
self.model._init_weights(self.classification_head.out_proj)
[docs] @add_start_docstrings_to_callable(BART_INPUTS_DOCSTRING)
@add_code_sample_docstrings(
tokenizer_class=_TOKENIZER_FOR_DOC,
checkpoint="facebook/bart-large",
output_type=Seq2SeqSequenceClassifierOutput,
config_class=_CONFIG_FOR_DOC,
)
def forward(
self,
input_ids,
attention_mask=None,
decoder_input_ids=None,
decoder_attention_mask=None,
encoder_outputs=None,
labels=None,
use_cache=None,
output_attentions=None,
output_hidden_states=None,
return_dict=None,
):
r"""
labels (:obj:`torch.LongTensor` of shape :obj:`(batch_size,)`, `optional`):
Labels for computing the sequence classification/regression loss.
Indices should be in :obj:`[0, ..., config.num_labels - 1]`.
If :obj:`config.num_labels > 1` a classification loss is computed (Cross-Entropy).
"""
return_dict = return_dict if return_dict is not None else self.config.use_return_dict
if labels is not None:
use_cache = False
outputs = self.model(
input_ids,
attention_mask=attention_mask,
decoder_input_ids=decoder_input_ids,
decoder_attention_mask=decoder_attention_mask,
encoder_outputs=encoder_outputs,
use_cache=use_cache,
output_attentions=output_attentions,
output_hidden_states=output_hidden_states,
return_dict=return_dict,
)
x = outputs[0] # last hidden state
eos_mask = input_ids.eq(self.config.eos_token_id)
if len(torch.unique(eos_mask.sum(1))) > 1:
raise ValueError("All examples must have the same number of <eos> tokens.")
sentence_representation = x[eos_mask, :].view(x.size(0), -1, x.size(-1))[:, -1, :]
logits = self.classification_head(sentence_representation)
loss = None
if labels is not None:
loss_fct = CrossEntropyLoss()
loss = loss_fct(logits.view(-1, self.config.num_labels), labels.view(-1))
if not return_dict:
output = (logits,) + outputs[1:]
return ((loss,) + output) if loss is not None else output
return Seq2SeqSequenceClassifierOutput(
loss=loss,
logits=logits,
past_key_values=outputs.past_key_values,
decoder_hidden_states=outputs.decoder_hidden_states,
decoder_attentions=outputs.decoder_attentions,
encoder_last_hidden_state=outputs.encoder_last_hidden_state,
encoder_hidden_states=outputs.encoder_hidden_states,
encoder_attentions=outputs.encoder_attentions,
)
[docs]@add_start_docstrings(
"""BART Model with a span classification head on top for extractive question-answering tasks like SQuAD (a linear layer on top of
the hidden-states output to compute `span start logits` and `span end logits`). """,
BART_START_DOCSTRING,
)
class BartForQuestionAnswering(PretrainedBartModel):
def __init__(self, config):
super().__init__(config)
config.num_labels = 2
self.num_labels = config.num_labels
self.model = BartModel(config)
self.qa_outputs = nn.Linear(config.hidden_size, config.num_labels)
self.model._init_weights(self.qa_outputs)
[docs] @add_start_docstrings_to_callable(BART_INPUTS_DOCSTRING)
@add_code_sample_docstrings(
tokenizer_class=_TOKENIZER_FOR_DOC,
checkpoint="facebook/bart-large",
output_type=Seq2SeqQuestionAnsweringModelOutput,
config_class=_CONFIG_FOR_DOC,
)
def forward(
self,
input_ids,
attention_mask=None,
decoder_input_ids=None,
decoder_attention_mask=None,
encoder_outputs=None,
start_positions=None,
end_positions=None,
use_cache=None,
output_attentions=None,
output_hidden_states=None,
return_dict=None,
):
r"""
start_positions (:obj:`torch.LongTensor` of shape :obj:`(batch_size,)`, `optional`):
Labels for position (index) of the start of the labelled span for computing the token classification loss.
Positions are clamped to the length of the sequence (`sequence_length`).
Position outside of the sequence are not taken into account for computing the loss.
end_positions (:obj:`torch.LongTensor` of shape :obj:`(batch_size,)`, `optional`):
Labels for position (index) of the end of the labelled span for computing the token classification loss.
Positions are clamped to the length of the sequence (`sequence_length`).
Position outside of the sequence are not taken into account for computing the loss.
"""
return_dict = return_dict if return_dict is not None else self.config.use_return_dict
if start_positions is not None and end_positions is not None:
use_cache = False
outputs = self.model(
input_ids,
attention_mask=attention_mask,
decoder_input_ids=decoder_input_ids,
decoder_attention_mask=decoder_attention_mask,
encoder_outputs=encoder_outputs,
use_cache=use_cache,
output_attentions=output_attentions,
output_hidden_states=output_hidden_states,
return_dict=return_dict,
)
sequence_output = outputs[0]
logits = self.qa_outputs(sequence_output)
start_logits, end_logits = logits.split(1, dim=-1)
start_logits = start_logits.squeeze(-1)
end_logits = end_logits.squeeze(-1)
total_loss = None
if start_positions is not None and end_positions is not None:
# If we are on multi-GPU, split add a dimension
if len(start_positions.size()) > 1:
start_positions = start_positions.squeeze(-1)
if len(end_positions.size()) > 1:
end_positions = end_positions.squeeze(-1)
# sometimes the start/end positions are outside our model inputs, we ignore these terms
ignored_index = start_logits.size(1)
start_positions.clamp_(0, ignored_index)
end_positions.clamp_(0, ignored_index)
loss_fct = CrossEntropyLoss(ignore_index=ignored_index)
start_loss = loss_fct(start_logits, start_positions)
end_loss = loss_fct(end_logits, end_positions)
total_loss = (start_loss + end_loss) / 2
if not return_dict:
output = (
start_logits,
end_logits,
) + outputs[1:]
return ((total_loss,) + output) if total_loss is not None else output
return Seq2SeqQuestionAnsweringModelOutput(
loss=total_loss,
start_logits=start_logits,
end_logits=end_logits,
past_key_values=outputs.past_key_values,
decoder_hidden_states=outputs.decoder_hidden_states,
decoder_attentions=outputs.decoder_attentions,
encoder_last_hidden_state=outputs.encoder_last_hidden_state,
encoder_hidden_states=outputs.encoder_hidden_states,
encoder_attentions=outputs.encoder_attentions,
)
[docs]class SinusoidalPositionalEmbedding(nn.Embedding):
"""This module produces sinusoidal positional embeddings of any length."""
def __init__(self, num_positions, embedding_dim, padding_idx=None):
super().__init__(num_positions, embedding_dim)
if embedding_dim % 2 != 0:
raise NotImplementedError(f"odd embedding_dim {embedding_dim} not supported")
self.weight = self._init_weight(self.weight)
@staticmethod
def _init_weight(out: nn.Parameter):
"""Identical to the XLM create_sinusoidal_embeddings except features are not interleaved.
The cos features are in the 2nd half of the vector. [dim // 2:]
"""
n_pos, dim = out.shape
position_enc = np.array(
[[pos / np.power(10000, 2 * (j // 2) / dim) for j in range(dim)] for pos in range(n_pos)]
)
out[:, 0: dim // 2] = torch.FloatTensor(np.sin(position_enc[:, 0::2])) # This line breaks for odd n_pos
out[:, dim // 2:] = torch.FloatTensor(np.cos(position_enc[:, 1::2]))
out.detach_()
out.requires_grad = False
return out
[docs] @torch.no_grad()
def forward(self, input_ids, use_cache=False):
"""Input is expected to be of size [bsz x seqlen]."""
bsz, seq_len = input_ids.shape[:2]
if use_cache:
positions = input_ids.data.new(1, 1).fill_(seq_len - 1) # called before slicing
else:
# starts at 0, ends at 1-seq_len
positions = torch.arange(seq_len, dtype=torch.long, device=self.weight.device)
return super().forward(positions)