File size: 22,695 Bytes
d5175d3 |
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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 |
# 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.
import math
from collections import namedtuple
import torch
import torch.nn as nn
import torch.nn.functional as F
from fairseq import options, utils
from fairseq.modules import (
AdaptiveSoftmax,
LayerNorm,
MultiheadAttention,
PositionalEmbedding,
)
EncoderOut = namedtuple(
"TransformerEncoderOut",
[
"encoder_out", # T x B x C
"encoder_padding_mask", # B x T
"encoder_embedding", # B x T x C
"encoder_states", # List[T x B x C]
],
)
class TransformerEncoderEmbedding(nn.Module):
""" Encoder Embedding + Positional Embedding """
def __init__(self, args, embed_tokens):
super().__init__()
self.dropout = args.dropout
self.max_source_positions = args.max_source_positions
self.embed_tokens = embed_tokens
if isinstance(embed_tokens, nn.ModuleList):
self.padding_idx = embed_tokens[0].padding_idx
embed_dim = sum(e.embedding_dim for e in embed_tokens)
else:
self.padding_idx = embed_tokens.padding_idx
embed_dim = embed_tokens.embedding_dim
self.embed_scale = math.sqrt(embed_dim)
self.embed_positions = (
PositionalEmbedding(
args.max_source_positions,
embed_dim,
self.padding_idx,
learned=args.encoder_learned_pos,
)
if not args.no_token_positional_embeddings
else None
)
if getattr(args, "layernorm_embedding", False):
self.layernorm_embedding = LayerNorm(embed_dim)
else:
self.layernorm_embedding = None
def forward(self, input):
# embed tokens and positions
src_tokens = input[0]
prev_output_tokens = input[2]
if isinstance(self.embed_tokens, nn.ModuleList):
x_embed_list = []
for embed_tokens_part in self.embed_tokens:
x_embed_list.append(embed_tokens_part(src_tokens))
embedded = torch.cat(x_embed_list, dim=-1)
else:
embedded = self.embed_tokens(src_tokens)
x = embed = self.embed_scale * embedded
if self.embed_positions is not None:
x = embed + self.embed_positions(src_tokens)
if self.layernorm_embedding:
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)
# compute padding mask
encoder_padding_mask = src_tokens.eq(self.padding_idx)
return (x, encoder_padding_mask, prev_output_tokens)
class TransformerEncoderLayerNorm(nn.Module):
"""
Layer norm at the the end of all encoder layers if
args.encoder_enormalize_before = True
"""
def __init__(self, args, embed_dim):
super().__init__()
if args.encoder_normalize_before:
self.layer_norm = LayerNorm(embed_dim)
else:
self.layer_norm = None
def forward(self, input):
x = input[0]
encoder_padding_mask = input[1]
prev_output_tokens = input[2]
if self.layer_norm:
x = self.layer_norm(x)
# keeping track of the incremental_state is not supported yet
return (x, encoder_padding_mask, prev_output_tokens)
class TransformerDecoderEmbedding(nn.Module):
""" Decoder Embedding + Positional Embedding """
def __init__(self, args, embed_tokens):
super().__init__()
self.dropout = args.dropout
self.share_input_output_embed = args.share_decoder_input_output_embed
input_embed_dim = (
sum(e.embedding_dim for e in embed_tokens)
if isinstance(embed_tokens, nn.ModuleList)
else embed_tokens.embedding_dim
)
embed_dim = args.decoder_embed_dim
self.output_embed_dim = args.decoder_output_dim
padding_idx = (
embed_tokens[0].padding_idx
if isinstance(embed_tokens, nn.ModuleList)
else embed_tokens.padding_idx
)
self.max_target_positions = args.max_target_positions
self.embed_tokens = embed_tokens
self.embed_scale = math.sqrt(embed_dim) # todo: try with input_embed_dim
self.project_in_dim = (
Linear(input_embed_dim, embed_dim, bias=False)
if embed_dim != input_embed_dim
else None
)
self.embed_positions = (
PositionalEmbedding(
args.max_target_positions,
embed_dim,
padding_idx,
learned=args.decoder_learned_pos,
)
if not args.no_token_positional_embeddings
else None
)
def forward(self, input):
mt_task = False
if isinstance(input, tuple):
if len(input) == 3:
encoder_out = input[0]
encoder_padding_mask = input[1]
prev_output_tokens = input[2]
incremental_state = None # Hardcoding to avoid passing of None objects
mt_task = True
else:
# HACK for now, need to fix (TODO sidgoyal)
prev_output_tokens = input[0]
# discard "src_lengths"
encoder_out = None
encoder_padding_mask = None
incremental_state = None
else:
prev_output_tokens = input
encoder_out = None
encoder_padding_mask = None
incremental_state = None
positions = (
self.embed_positions(
prev_output_tokens,
incremental_state=incremental_state,
)
if self.embed_positions is not None
else None
)
if incremental_state is not None:
prev_output_tokens = prev_output_tokens[:, -1:]
if positions is not None:
positions = positions[:, -1:]
# embed tokens and positions
if isinstance(self.embed_tokens, nn.ModuleList):
x_embed_list = []
for embed_tokens_part in self.embed_tokens:
x_embed_list.append(embed_tokens_part(prev_output_tokens))
x = self.embed_scale * torch.cat(x_embed_list, dim=-1)
else:
x = self.embed_scale * self.embed_tokens(prev_output_tokens)
if self.project_in_dim is not None:
x = self.project_in_dim(x)
if positions is not None:
x += positions
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)
if mt_task:
return (x, encoder_out, encoder_padding_mask)
return x
class TransformerDecoderOutputLayer(nn.Module):
def __init__(self, args, embed_tokens, dictionary):
super().__init__()
self.share_input_output_embed = args.share_decoder_input_output_embed
self.embed_tokens = embed_tokens
self.output_embed_dim = args.decoder_output_dim
embed_dim = args.decoder_embed_dim
self.project_out_dim = (
Linear(embed_dim, self.output_embed_dim, bias=False)
if embed_dim != self.output_embed_dim and not args.tie_adaptive_weights
else None
)
self.adaptive_softmax = None
if args.adaptive_softmax_cutoff is not None:
assert not isinstance(embed_tokens, nn.ModuleList)
self.adaptive_softmax = AdaptiveSoftmax(
len(dictionary),
self.output_embed_dim,
options.eval_str_list(args.adaptive_softmax_cutoff, type=int),
dropout=args.adaptive_softmax_dropout,
adaptive_inputs=embed_tokens if args.tie_adaptive_weights else None,
factor=args.adaptive_softmax_factor,
tie_proj=args.tie_adaptive_proj,
)
elif not self.share_input_output_embed:
self.embed_tokens = nn.Parameter(
torch.Tensor(len(dictionary), self.output_embed_dim)
)
nn.init.normal_(
self.embed_tokens, mean=0, std=self.output_embed_dim ** -0.5
)
if args.decoder_normalize_before and not getattr(
args, "no_decoder_final_norm", False
):
self.layer_norm = LayerNorm(embed_dim)
else:
self.layer_norm = None
def forward(self, input, apply_final_proj=True):
if isinstance(input, tuple):
x = input[0]
else:
x = input
if self.layer_norm:
x = self.layer_norm(x)
# T x B x C -> B x T x C
x = x.transpose(0, 1)
if self.project_out_dim is not None:
x = self.project_out_dim(x)
if apply_final_proj:
x = self.output_layer(x)
return x
def output_layer(self, features, **kwargs):
"""Project features to the vocabulary size."""
if self.adaptive_softmax is None:
# project back to size of vocabulary
if self.share_input_output_embed:
if isinstance(self.embed_tokens, nn.ModuleList):
output = None
for i, emb in enumerate(self.embed_tokens):
sidx = i * emb.embedding_dim
eidx = (i + 1) * emb.embedding_dim
if output is None:
output = F.linear(features[:, :, sidx:eidx], emb.weight)
else:
output += F.linear(features[:, :, sidx:eidx], emb.weight)
return output
else:
return F.linear(features, self.embed_tokens.weight)
else:
return F.linear(features, self.embed_tokens)
else:
return features
class TransformerEncoderLayer(nn.Module):
"""Encoder layer block.
In the original paper each operation (multi-head attention or FFN) is
postprocessed with: `dropout -> add residual -> layernorm`. In the
tensor2tensor code they suggest that learning is more robust when
preprocessing each layer with layernorm and postprocessing with:
`dropout -> add residual`. We default to the approach in the paper, but the
tensor2tensor approach can be enabled by setting
*args.encoder_normalize_before* to ``True``.
Args:
args (argparse.Namespace): parsed command-line arguments
"""
def __init__(self, args):
super().__init__()
self.embed_dim = args.encoder_embed_dim
self.self_attn = MultiheadAttention(
self.embed_dim,
args.encoder_attention_heads,
dropout=args.attention_dropout,
self_attention=True,
)
self.self_attn_layer_norm = LayerNorm(self.embed_dim)
self.dropout = args.dropout
self.activation_fn = utils.get_activation_fn(
activation=getattr(args, "activation_fn", "relu")
)
self.activation_dropout = getattr(args, "activation_dropout", 0)
if self.activation_dropout == 0:
# for backwards compatibility with models that use args.relu_dropout
self.activation_dropout = getattr(args, "relu_dropout", 0)
self.normalize_before = args.encoder_normalize_before
self.fc1 = Linear(self.embed_dim, args.encoder_ffn_embed_dim)
self.fc2 = Linear(args.encoder_ffn_embed_dim, self.embed_dim)
self.final_layer_norm = LayerNorm(self.embed_dim)
def upgrade_state_dict_named(self, state_dict, name):
"""
Rename layer norm states from `...layer_norms.0.weight` to
`...self_attn_layer_norm.weight` and `...layer_norms.1.weight` to
`...final_layer_norm.weight`
"""
layer_norm_map = {"0": "self_attn_layer_norm", "1": "final_layer_norm"}
for old, new in layer_norm_map.items():
for m in ("weight", "bias"):
k = "{}.layer_norms.{}.{}".format(name, old, m)
if k in state_dict:
state_dict["{}.{}.{}".format(name, new, m)] = state_dict[k]
del state_dict[k]
def forward(self, input):
"""
Args:
input (Tuple):
input[0] (Tensor): input to the layer of shape `(seq_len, batch, embed_dim)`
input[1] (ByteTensor/FloatTensor): encoder padding mask -
binary ByteTensor of shape `(batch, src_len)` where padding elements
are indicated by ``1``.
input[2] (LongTensor): previous decoder outputs of shape
`(batch, tgt_len)`, for teacher forcing)
Returns:
output (Tuple):
output[0] (Tensor): encoded output of shape `(batch, src_len, embed_dim)`
output[1] (ByteTensor/FloatTensor): encoder padding mask
output[2] (LongTensor): previous decoder outputs
"""
x = input[0]
encoder_padding_mask = input[1]
prev_output_tokens = input[2]
residual = x
x = self.maybe_layer_norm(self.self_attn_layer_norm, x, before=True)
x, _ = self.self_attn(
query=x, key=x, value=x, key_padding_mask=encoder_padding_mask
)
x = F.dropout(x, p=self.dropout, training=self.training)
x = residual + x
x = self.maybe_layer_norm(self.self_attn_layer_norm, x, after=True)
residual = x
x = self.maybe_layer_norm(self.final_layer_norm, x, before=True)
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
x = self.maybe_layer_norm(self.final_layer_norm, x, after=True)
return (x, encoder_padding_mask, prev_output_tokens)
def maybe_layer_norm(self, layer_norm, x, before=False, after=False):
assert before ^ after
if after ^ self.normalize_before:
return layer_norm(x)
else:
return x
class TransformerDecoderLayer(nn.Module):
"""Decoder layer block.
In the original paper each operation (multi-head attention, encoder
attention or FFN) is postprocessed with: `dropout -> add residual ->
layernorm`. In the tensor2tensor code they suggest that learning is more
robust when preprocessing each layer with layernorm and postprocessing with:
`dropout -> add residual`. We default to the approach in the paper, but the
tensor2tensor approach can be enabled by setting
*args.decoder_normalize_before* to ``True``.
Args:
args (argparse.Namespace): parsed command-line arguments
no_encoder_attn (bool, optional): whether to attend to encoder outputs
(default: False).
"""
def __init__(
self, args, no_encoder_attn=False, add_bias_kv=False, add_zero_attn=False
):
super().__init__()
self.embed_dim = args.decoder_embed_dim
self.self_attn = MultiheadAttention(
embed_dim=self.embed_dim,
num_heads=args.decoder_attention_heads,
dropout=args.attention_dropout,
add_bias_kv=add_bias_kv,
add_zero_attn=add_zero_attn,
self_attention=True,
)
self.dropout = args.dropout
self.activation_fn = utils.get_activation_fn(
activation=getattr(args, "activation_fn", "relu")
)
self.activation_dropout = getattr(args, "activation_dropout", 0)
if self.activation_dropout == 0:
# for backwards compatibility with models that use args.relu_dropout
self.activation_dropout = getattr(args, "relu_dropout", 0)
self.normalize_before = args.decoder_normalize_before
# use layerNorm rather than FusedLayerNorm for exporting.
# char_inputs can be used to determint this.
# TODO remove this once we update apex with the fix
export = getattr(args, "char_inputs", False)
self.self_attn_layer_norm = LayerNorm(self.embed_dim, export=export)
if no_encoder_attn:
self.encoder_attn = None
self.encoder_attn_layer_norm = None
else:
self.encoder_attn = MultiheadAttention(
self.embed_dim,
args.decoder_attention_heads,
kdim=getattr(args, "encoder_embed_dim", None),
vdim=getattr(args, "encoder_embed_dim", None),
dropout=args.attention_dropout,
encoder_decoder_attention=True,
)
self.encoder_attn_layer_norm = LayerNorm(self.embed_dim, export=export)
self.fc1 = Linear(self.embed_dim, args.decoder_ffn_embed_dim)
self.fc2 = Linear(args.decoder_ffn_embed_dim, self.embed_dim)
self.final_layer_norm = LayerNorm(self.embed_dim, export=export)
self.need_attn = True
self.onnx_trace = False
def prepare_for_onnx_export_(self):
self.onnx_trace = True
def forward(self, input):
"""
Args:
input (Tuple):
input[0] (Tensor): input to the layer of shape `(seq_len, batch, embed_dim)`
input[1] (Tensor): encoder output of shape `(batch, src_len, embed_dim)`
input[2] (ByteTensor/FloatTensor): encoder padding mask -
binary ByteTensor of shape `(batch, src_len)` where padding elements
are indicated by ``1``.
Returns:
output (Tuple):
output[0] (Tensor): encoded output of shape `(batch, src_len, embed_dim)`
output[1] (ByteTensor/FloatTensor): encoder padding mask
output[2] (LongTensor): previous decoder outputs
"""
# Note: incremental state is not yet supported
mt_task = False
if isinstance(input, tuple):
x = input[0]
encoder_out = input[1]
encoder_padding_mask = input[2]
incremental_state = None
mt_task = True
else:
x = input
encoder_out = None
encoder_padding_mask = None
incremental_state = None
if incremental_state is None:
self_attn_mask = self.buffered_future_mask(x)
else:
self_attn_mask = None
# TODO: add back prev_self_attn_state, prev_attn_state,
# self_attn_padding_mask
prev_self_attn_state = None
prev_attn_state = None
self_attn_padding_mask = None
residual = x
x = self.maybe_layer_norm(self.self_attn_layer_norm, x, before=True)
if prev_self_attn_state is not None:
if incremental_state is None:
incremental_state = {}
prev_key, prev_value = prev_self_attn_state
saved_state = {"prev_key": prev_key, "prev_value": prev_value}
self.self_attn._set_input_buffer(incremental_state, saved_state)
x, attn = self.self_attn(
query=x,
key=x,
value=x,
key_padding_mask=self_attn_padding_mask,
incremental_state=incremental_state,
need_weights=False,
attn_mask=self_attn_mask,
)
x = F.dropout(x, p=self.dropout, training=self.training)
x = residual + x
x = self.maybe_layer_norm(self.self_attn_layer_norm, x, after=True)
if self.encoder_attn is not None:
residual = x
x = self.maybe_layer_norm(self.encoder_attn_layer_norm, x, before=True)
if prev_attn_state is not None:
if incremental_state is None:
incremental_state = {}
prev_key, prev_value = prev_attn_state
saved_state = {"prev_key": prev_key, "prev_value": prev_value}
self.encoder_attn._set_input_buffer(incremental_state, saved_state)
x, attn = self.encoder_attn(
query=x,
key=encoder_out,
value=encoder_out,
key_padding_mask=encoder_padding_mask,
incremental_state=incremental_state,
static_kv=True,
need_weights=(not self.training and self.need_attn),
)
x = F.dropout(x, p=self.dropout, training=self.training)
x = residual + x
x = self.maybe_layer_norm(self.encoder_attn_layer_norm, x, after=True)
residual = x
x = self.maybe_layer_norm(self.final_layer_norm, x, before=True)
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
x = self.maybe_layer_norm(self.final_layer_norm, x, after=True)
if mt_task:
return (x, encoder_out, encoder_padding_mask)
return x
def buffered_future_mask(self, tensor):
dim = tensor.size(0)
if (
not hasattr(self, "_future_mask")
or self._future_mask is None
or self._future_mask.device != tensor.device
):
self._future_mask = torch.triu(
utils.fill_with_neg_inf(tensor.new(dim, dim)), 1
)
if self._future_mask.size(0) < dim:
self._future_mask = torch.triu(
utils.fill_with_neg_inf(self._future_mask.resize_(dim, dim)), 1
)
return self._future_mask[:dim, :dim]
def maybe_layer_norm(self, layer_norm, x, before=False, after=False):
assert before ^ after
if after ^ self.normalize_before:
return layer_norm(x)
else:
return x
def make_generation_fast_(self, need_attn=False, **kwargs):
self.need_attn = need_attn
def Embedding(num_embeddings, embedding_dim, padding_idx):
m = nn.Embedding(num_embeddings, embedding_dim, padding_idx=padding_idx)
nn.init.normal_(m.weight, mean=0, std=embedding_dim ** -0.5)
nn.init.constant_(m.weight[padding_idx], 0)
return m
def Linear(in_features, out_features, bias=True):
m = nn.Linear(in_features, out_features, bias)
nn.init.xavier_uniform_(m.weight)
if bias:
nn.init.constant_(m.bias, 0.0)
return m
|