File size: 10,367 Bytes
be611b4 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 |
# 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.
"""
RoBERTa: A Robustly Optimized BERT Pretraining Approach.
"""
import logging
import torch
import torch.nn as nn
import torch.nn.functional as F
from fairseq import utils
from fairseq.models import (
FairseqEncoder,
register_model,
register_model_architecture,
)
from fairseq.models.roberta import (
RobertaModel,
RobertaEncoder,
RobertaLMHead,
RobertaClassificationHead,
)
from fairseq.modules import (
LayerNorm,
TransformerSentenceEncoder,
)
from fairseq.model_parallel.modules import (
ModelParallelTransformerSentenceEncoder,
)
from fairseq.modules.transformer_sentence_encoder import init_bert_params
try:
from fairseq.model_parallel.megatron.mpu import (
copy_to_model_parallel_region,
gather_from_model_parallel_region,
ColumnParallelLinear,
RowParallelLinear,
)
has_megatron_submodule = True
except (ImportError, ModuleNotFoundError):
has_megatron_submodule = False
logger = logging.getLogger(__name__)
@register_model('model_parallel_roberta')
class ModelParallelRobertaModel(RobertaModel):
def __init__(self, args, encoder):
super().__init__(args, encoder)
self.classification_heads = nn.ModuleDict()
@staticmethod
def add_args(parser):
super(ModelParallelRobertaModel, ModelParallelRobertaModel).add_args(parser)
@classmethod
def build_model(cls, args, task):
"""Build a new model instance."""
# make sure all arguments are present
base_architecture(args)
if not hasattr(args, 'max_positions'):
args.max_positions = args.tokens_per_sample
encoder = ModelParallelRobertaEncoder(args, task.source_dictionary)
return cls(args, encoder)
def forward(self, src_tokens, features_only=False, return_all_hiddens=False, classification_head_name=None, **kwargs):
if classification_head_name is not None:
features_only = True
x, extra = self.encoder(src_tokens, features_only, return_all_hiddens, **kwargs)
if classification_head_name is not None:
x = self.classification_heads[classification_head_name](x)
return x, extra
def register_classification_head(self, name, num_classes=None, inner_dim=None, **kwargs):
"""Register a classification head."""
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] = ModelParallelRobertaClassificationHead(
self.args.encoder_embed_dim,
inner_dim or self.args.encoder_embed_dim,
num_classes,
self.args.pooler_activation_fn,
self.args.pooler_dropout,
)
class ModelParallelRobertaLMHead(nn.Module):
"""Head for masked language modeling."""
def __init__(self, embed_dim, output_dim, activation_fn, weight=None):
super().__init__()
self.dense = ColumnParallelLinear(embed_dim, embed_dim, gather_output=True)
self.activation_fn = utils.get_activation_fn(activation_fn)
self.layer_norm = LayerNorm(embed_dim)
if weight is None:
weight = nn.Linear(embed_dim, output_dim, bias=False).weight
self.weight = weight
self.bias = nn.Parameter(torch.zeros(output_dim))
def forward(self, features, masked_tokens=None, **kwargs):
# Only project the unmasked tokens while training,
# saves both memory and computation
if masked_tokens is not None:
features = features[masked_tokens, :]
x = self.dense(features)
x = self.activation_fn(x)
x = self.layer_norm(x)
features = copy_to_model_parallel_region(features)
# project back to size of vocabulary with bias
x = F.linear(x, self.weight)
x = gather_from_model_parallel_region(x).contiguous()
x = x + self.bias
return x
class ModelParallelRobertaClassificationHead(nn.Module):
"""Head for sentence-level classification tasks."""
def __init__(self, input_dim, inner_dim, num_classes, activation_fn, pooler_dropout):
super().__init__()
self.dense = ColumnParallelLinear(input_dim, inner_dim, gather_output=True)
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)
def forward(self, features, **kwargs):
x = features[:, 0, :] # take <s> token (equiv. to [CLS])
x = self.dropout(x)
x = self.dense(x)
x = self.activation_fn(x)
x = self.dropout(x)
x = self.out_proj(x)
return x
class ModelParallelRobertaEncoder(FairseqEncoder):
"""RoBERTa encoder.
Implements the :class:`~fairseq.models.FairseqDecoder` interface required
by :class:`~fairseq.models.FairseqLanguageModel`.
"""
def __init__(self, args, dictionary):
super().__init__(dictionary)
self.args = args
# RoBERTa is a sentence encoder model, so users will intuitively trim
# encoder layers. However, the implementation uses the fairseq decoder,
# so we fix here.
if args.encoder_layers_to_keep:
args.encoder_layers = len(args.encoder_layers_to_keep.split(","))
args.decoder_layers_to_keep = args.encoder_layers_to_keep
args.encoder_layers_to_keep = None
self.sentence_encoder = ModelParallelTransformerSentenceEncoder(
padding_idx=dictionary.pad(),
vocab_size=len(dictionary),
num_encoder_layers=args.encoder_layers,
embedding_dim=args.encoder_embed_dim,
ffn_embedding_dim=args.encoder_ffn_embed_dim,
num_attention_heads=args.encoder_attention_heads,
dropout=args.dropout,
attention_dropout=args.attention_dropout,
activation_dropout=args.activation_dropout,
layerdrop=args.encoder_layerdrop,
max_seq_len=args.max_positions,
num_segments=0,
encoder_normalize_before=False,
apply_bert_init=False,
activation_fn=args.activation_fn,
)
self.lm_head = ModelParallelRobertaLMHead(
embed_dim=args.encoder_embed_dim,
output_dim=len(dictionary),
activation_fn=args.activation_fn,
weight=self.sentence_encoder.embed_tokens.weight,
)
def forward(self, src_tokens, features_only=False, return_all_hiddens=False, masked_tokens=None, **unused):
"""
Args:
src_tokens (LongTensor): input tokens of shape `(batch, src_len)`
features_only (bool, optional): skip LM head and just return
features. If True, the output will be of shape
`(batch, src_len, embed_dim)`.
return_all_hiddens (bool, optional): also return all of the
intermediate hidden states (default: False).
Returns:
tuple:
- the LM output of shape `(batch, src_len, vocab)`
- a dictionary of additional data, where 'inner_states'
is a list of hidden states. Note that the hidden
states have shape `(src_len, batch, vocab)`.
"""
x, extra = self.extract_features(src_tokens, return_all_hiddens=return_all_hiddens)
if not features_only:
x = self.output_layer(x, masked_tokens=masked_tokens)
return x, extra
def extract_features(self, src_tokens, return_all_hiddens=False, **unused):
inner_states, _ = self.sentence_encoder(
src_tokens,
last_state_only=not return_all_hiddens,
)
features = inner_states[-1].transpose(0, 1) # T x B x C -> B x T x C
return features, {'inner_states': inner_states if return_all_hiddens else None}
def output_layer(self, features, masked_tokens=None, **unused):
return self.lm_head(features, masked_tokens)
def max_positions(self):
"""Maximum output length supported by the encoder."""
return self.args.max_positions
@register_model_architecture('model_parallel_roberta', 'model_parallel_roberta')
def base_architecture(args):
args.encoder_layers = getattr(args, 'encoder_layers', 12)
args.encoder_embed_dim = getattr(args, 'encoder_embed_dim', 768)
args.encoder_ffn_embed_dim = getattr(args, 'encoder_ffn_embed_dim', 3072)
args.encoder_attention_heads = getattr(args, 'encoder_attention_heads', 12)
args.activation_fn = getattr(args, 'activation_fn', 'gelu')
args.pooler_activation_fn = getattr(args, 'pooler_activation_fn', 'tanh')
args.dropout = getattr(args, 'dropout', 0.1)
args.attention_dropout = getattr(args, 'attention_dropout', 0.1)
args.activation_dropout = getattr(args, 'activation_dropout', 0.0)
args.pooler_dropout = getattr(args, 'pooler_dropout', 0.0)
args.encoder_layers_to_keep = getattr(args, 'encoder_layers_to_keep', None)
args.encoder_layerdrop = getattr(args, 'encoder_layerdrop', 0.0)
@register_model_architecture('model_parallel_roberta', 'model_parallel_roberta_base')
def roberta_base_architecture(args):
base_architecture(args)
@register_model_architecture('model_parallel_roberta', 'model_parallel_roberta_large')
def roberta_large_architecture(args):
args.encoder_layers = getattr(args, 'encoder_layers', 24)
args.encoder_embed_dim = getattr(args, 'encoder_embed_dim', 1024)
args.encoder_ffn_embed_dim = getattr(args, 'encoder_ffn_embed_dim', 4096)
args.encoder_attention_heads = getattr(args, 'encoder_attention_heads', 16)
base_architecture(args)
|