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chore: import upstream snapshot with attribution

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# 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.
"""
BART: Denoising Sequence-to-Sequence Pre-training for
Natural Language Generation, Translation, and Comprehension
"""
from typing import Optional
import logging
import torch
import torch.nn as nn
from fairseq import utils
from fairseq.models import register_model, register_model_architecture
from fairseq.models.transformer import TransformerModel
from fairseq.modules.transformer_sentence_encoder import init_bert_params
from .hub_interface import BARTHubInterface
logger = logging.getLogger(__name__)
@register_model("bart")
class BARTModel(TransformerModel):
__jit_unused_properties__ = ["supported_targets"]
@classmethod
def hub_models(cls):
return {
"bart.base": "http://dl.fbaipublicfiles.com/fairseq/models/bart.base.tar.gz",
"bart.large": "http://dl.fbaipublicfiles.com/fairseq/models/bart.large.tar.gz",
"bart.large.mnli": "http://dl.fbaipublicfiles.com/fairseq/models/bart.large.mnli.tar.gz",
"bart.large.cnn": "http://dl.fbaipublicfiles.com/fairseq/models/bart.large.cnn.tar.gz",
"bart.large.xsum": "http://dl.fbaipublicfiles.com/fairseq/models/bart.large.xsum.tar.gz",
}
def __init__(self, args, encoder, decoder):
super().__init__(args, encoder, decoder)
# We follow BERT's random weight initialization
self.apply(init_bert_params)
self.classification_heads = nn.ModuleDict()
if hasattr(self.encoder, "dictionary"):
self.eos: int = self.encoder.dictionary.eos()
@staticmethod
def add_args(parser):
super(BARTModel, BARTModel).add_args(parser)
parser.add_argument(
"--pooler-dropout",
type=float,
metavar="D",
help="dropout probability in the masked_lm pooler layers",
)
parser.add_argument(
"--pooler-activation-fn",
choices=utils.get_available_activation_fns(),
help="activation function to use for pooler layer",
)
parser.add_argument(
"--spectral-norm-classification-head",
action="store_true",
help="Apply spectral normalization on the classification head",
)
@property
def supported_targets(self):
return {"self"}
def forward(
self,
src_tokens,
src_lengths,
prev_output_tokens,
features_only: bool = False,
classification_head_name: Optional[str] = None,
token_embeddings: Optional[torch.Tensor] = None,
return_all_hiddens: bool = True,
alignment_layer: Optional[int] = None,
alignment_heads: Optional[int] = None,
):
if classification_head_name is not None:
features_only = True
encoder_out = self.encoder(
src_tokens,
src_lengths=src_lengths,
token_embeddings=token_embeddings,
return_all_hiddens=return_all_hiddens
)
x, extra = self.decoder(
prev_output_tokens,
encoder_out=encoder_out,
features_only=features_only,
alignment_layer=alignment_layer,
alignment_heads=alignment_heads,
src_lengths=src_lengths,
return_all_hiddens=return_all_hiddens,
)
eos: int = self.eos
if classification_head_name is not None:
sentence_representation = x[
src_tokens.eq(eos), :
].view(x.size(0), -1, x.size(-1))[:, -1, :]
for k, head in self.classification_heads.items():
# for torch script only supports iteration
if k == classification_head_name:
x = head(sentence_representation)
break
return x, extra
@classmethod
def from_pretrained(
cls,
model_name_or_path,
checkpoint_file="model.pt",
data_name_or_path=".",
bpe="gpt2",
sample_break_mode="eos",
**kwargs,
):
from fairseq import hub_utils
x = hub_utils.from_pretrained(
model_name_or_path,
checkpoint_file,
data_name_or_path,
archive_map=cls.hub_models(),
bpe=bpe,
load_checkpoint_heads=True,
sample_break_mode=sample_break_mode,
**kwargs,
)
return BARTHubInterface(x["args"], x["task"], x["models"][0])
def register_classification_head(
self, name, num_classes=None, inner_dim=None, **kwargs
):
"""Register a classification head."""
logger.info("Registering classification head: {0}".format(name))
if name in self.classification_heads:
prev_num_classes = self.classification_heads[name].out_proj.out_features
prev_inner_dim = self.classification_heads[name].dense.out_features
if num_classes != prev_num_classes or inner_dim != prev_inner_dim:
logger.warning(
're-registering head "{}" with num_classes {} (prev: {}) '
"and inner_dim {} (prev: {})".format(
name, num_classes, prev_num_classes, inner_dim, prev_inner_dim
)
)
self.classification_heads[name] = BARTClassificationHead(
input_dim=self.args.encoder_embed_dim,
inner_dim=inner_dim or self.args.encoder_embed_dim,
num_classes=num_classes,
activation_fn=self.args.pooler_activation_fn,
pooler_dropout=self.args.pooler_dropout,
do_spectral_norm=getattr(
self.args, "spectral_norm_classification_head", False
),
)
def upgrade_state_dict_named(self, state_dict, name):
super().upgrade_state_dict_named(state_dict, name)
prefix = name + "." if name != "" else ""
current_head_names = (
[]
if not hasattr(self, "classification_heads")
else self.classification_heads.keys()
)
# Handle new classification heads present in the state dict.
keys_to_delete = []
for k in state_dict.keys():
if not k.startswith(prefix + "classification_heads."):
continue
head_name = k[len(prefix + "classification_heads.") :].split(".")[0]
num_classes = state_dict[
prefix + "classification_heads." + head_name + ".out_proj.weight"
].size(0)
inner_dim = state_dict[
prefix + "classification_heads." + head_name + ".dense.weight"
].size(0)
if getattr(self.args, "load_checkpoint_heads", False):
if head_name not in current_head_names:
self.register_classification_head(head_name, num_classes, inner_dim)
else:
if head_name not in current_head_names:
logger.warning(
"deleting classification head ({}) from checkpoint "
"not present in current model: {}".format(head_name, k)
)
keys_to_delete.append(k)
elif (
num_classes
!= self.classification_heads[head_name].out_proj.out_features
or inner_dim
!= self.classification_heads[head_name].dense.out_features
):
logger.warning(
"deleting classification head ({}) from checkpoint "
"with different dimensions than current model: {}".format(
head_name, k
)
)
keys_to_delete.append(k)
for k in keys_to_delete:
del state_dict[k]
def truncate_emb(key):
if key in state_dict:
state_dict[key] = state_dict[key][:-1, :]
# When finetuning on translation task, remove last row of
# embedding matrix that corresponds to mask_idx token.
loaded_dict_size = state_dict["encoder.embed_tokens.weight"].size(0)
if (
loaded_dict_size == len(self.encoder.dictionary) + 1
and "<mask>" not in self.encoder.dictionary
):
truncate_emb("encoder.embed_tokens.weight")
truncate_emb("decoder.embed_tokens.weight")
truncate_emb("encoder.output_projection.weight")
truncate_emb("decoder.output_projection.weight")
# When continued pretraining on new set of languages for mbart,
# add extra lang embeddings at the end of embed_tokens.
# Note: newly added languages are assumed to have been added at the end.
if self.args.task == "multilingual_denoising" and loaded_dict_size < len(
self.encoder.dictionary
):
logger.info(
"Adding extra language embeddings not found in pretrained model for "
"continued pretraining of MBART on new set of languages."
)
loaded_mask_token_embedding = state_dict["encoder.embed_tokens.weight"][
-1, :
]
num_langids_to_add = len(self.encoder.dictionary) - loaded_dict_size
embed_dim = state_dict["encoder.embed_tokens.weight"].size(1)
new_lang_embed_to_add = torch.zeros(num_langids_to_add, embed_dim)
nn.init.normal_(new_lang_embed_to_add, mean=0, std=embed_dim ** -0.5)
new_lang_embed_to_add = new_lang_embed_to_add.to(
dtype=state_dict["encoder.embed_tokens.weight"].dtype,
)
state_dict["encoder.embed_tokens.weight"] = torch.cat(
[
state_dict["encoder.embed_tokens.weight"][
: loaded_dict_size - 1, :
],
new_lang_embed_to_add,
loaded_mask_token_embedding.unsqueeze(0),
]
)
state_dict["decoder.embed_tokens.weight"] = torch.cat(
[
state_dict["decoder.embed_tokens.weight"][
: loaded_dict_size - 1, :
],
new_lang_embed_to_add,
loaded_mask_token_embedding.unsqueeze(0),
]
)
# Copy any newly-added classification heads into the state dict
# with their current weights.
if hasattr(self, "classification_heads"):
cur_state = self.classification_heads.state_dict()
for k, v in cur_state.items():
if prefix + "classification_heads." + k not in state_dict:
logger.info("Overwriting " + prefix + "classification_heads." + k)
state_dict[prefix + "classification_heads." + k] = v
class BARTClassificationHead(nn.Module):
"""Head for sentence-level classification tasks."""
def __init__(
self,
input_dim,
inner_dim,
num_classes,
activation_fn,
pooler_dropout,
do_spectral_norm=False,
):
super().__init__()
self.dense = nn.Linear(input_dim, inner_dim)
self.activation_fn = utils.get_activation_fn(activation_fn)
self.dropout = nn.Dropout(p=pooler_dropout)
self.out_proj = nn.Linear(inner_dim, num_classes)
if do_spectral_norm:
self.out_proj = torch.nn.utils.spectral_norm(self.out_proj)
def forward(self, features, **kwargs):
x = features
x = self.dropout(x)
x = self.dense(x)
x = self.activation_fn(x)
x = self.dropout(x)
x = self.out_proj(x)
return x
@register_model_architecture("bart", "bart_large")
def bart_large_architecture(args):
args.encoder_embed_path = getattr(args, "encoder_embed_path", None)
args.encoder_embed_dim = getattr(args, "encoder_embed_dim", 1024)
args.encoder_ffn_embed_dim = getattr(args, "encoder_ffn_embed_dim", 4 * 1024)
args.encoder_layers = getattr(args, "encoder_layers", 12)
args.encoder_attention_heads = getattr(args, "encoder_attention_heads", 16)
args.encoder_normalize_before = getattr(args, "encoder_normalize_before", False)
args.encoder_learned_pos = getattr(args, "encoder_learned_pos", True)
args.decoder_embed_path = getattr(args, "decoder_embed_path", None)
args.decoder_embed_dim = getattr(args, "decoder_embed_dim", args.encoder_embed_dim)
args.decoder_ffn_embed_dim = getattr(
args, "decoder_ffn_embed_dim", args.encoder_ffn_embed_dim
)
args.decoder_layers = getattr(args, "decoder_layers", 12)
args.decoder_attention_heads = getattr(args, "decoder_attention_heads", 16)
args.decoder_normalize_before = getattr(args, "decoder_normalize_before", False)
args.decoder_learned_pos = getattr(args, "decoder_learned_pos", True)
args.attention_dropout = getattr(args, "attention_dropout", 0.0)
args.relu_dropout = getattr(args, "relu_dropout", 0.0)
args.dropout = getattr(args, "dropout", 0.1)
args.max_target_positions = getattr(args, "max_target_positions", 1024)
args.max_source_positions = getattr(args, "max_source_positions", 1024)
args.adaptive_softmax_cutoff = getattr(args, "adaptive_softmax_cutoff", None)
args.adaptive_softmax_dropout = getattr(args, "adaptive_softmax_dropout", 0)
args.share_decoder_input_output_embed = getattr(
args, "share_decoder_input_output_embed", True
)
args.share_all_embeddings = getattr(args, "share_all_embeddings", True)
args.decoder_output_dim = getattr(
args, "decoder_output_dim", args.decoder_embed_dim
)
args.decoder_input_dim = getattr(args, "decoder_input_dim", args.decoder_embed_dim)
args.no_scale_embedding = getattr(args, "no_scale_embedding", True)
args.layernorm_embedding = getattr(args, "layernorm_embedding", True)
args.activation_fn = getattr(args, "activation_fn", "gelu")
args.pooler_activation_fn = getattr(args, "pooler_activation_fn", "tanh")
args.pooler_dropout = getattr(args, "pooler_dropout", 0.0)
@register_model_architecture("bart", "bart_base")
def bart_base_architecture(args):
args.encoder_embed_dim = getattr(args, "encoder_embed_dim", 768)
args.encoder_ffn_embed_dim = getattr(args, "encoder_ffn_embed_dim", 4 * 768)
args.encoder_layers = getattr(args, "encoder_layers", 6)
args.encoder_attention_heads = getattr(args, "encoder_attention_heads", 12)
args.decoder_layers = getattr(args, "decoder_layers", 6)
args.decoder_attention_heads = getattr(args, "decoder_attention_heads", 12)
bart_large_architecture(args)
@register_model_architecture("bart", "mbart_large")
def mbart_large_architecture(args):
args.no_scale_embedding = getattr(args, "no_scale_embedding", False)
bart_large_architecture(args)
@register_model_architecture("bart", "mbart_base")
def mbart_base_architecture(args):
args.no_scale_embedding = getattr(args, "no_scale_embedding", False)
bart_base_architecture(args)
@register_model_architecture("bart", "mbart_base_wmt20")
def mbart_base_wmt20_architecture(args):
args.layernorm_embedding = getattr(args, "layernorm_embedding", False)
mbart_base_architecture(args)