Source code for fairseq.models.transformer
# Copyright (c) 2017-present, Facebook, Inc.
# All rights reserved.
#
# This source code is licensed under the license found in the LICENSE file in
# the root directory of this source tree. An additional grant of patent rights
# can be found in the PATENTS file in the same directory.
import math
import torch
import torch.nn as nn
import torch.nn.functional as F
from fairseq import options, utils
from fairseq.models import (
FairseqEncoder,
FairseqIncrementalDecoder,
FairseqEncoderDecoderModel,
register_model,
register_model_architecture,
)
from fairseq.modules import (
AdaptiveSoftmax,
LayerNorm,
MultiheadAttention,
PositionalEmbedding,
SinusoidalPositionalEmbedding,
)
DEFAULT_MAX_SOURCE_POSITIONS = 1024
DEFAULT_MAX_TARGET_POSITIONS = 1024
[docs]@register_model('transformer')
class TransformerModel(FairseqEncoderDecoderModel):
"""
Transformer model from `"Attention Is All You Need" (Vaswani, et al, 2017)
<https://arxiv.org/abs/1706.03762>`_.
Args:
encoder (TransformerEncoder): the encoder
decoder (TransformerDecoder): the decoder
The Transformer model provides the following named architectures and
command-line arguments:
.. argparse::
:ref: fairseq.models.transformer_parser
:prog:
"""
@classmethod
def hub_models(cls):
return {
'transformer.wmt14.en-fr': 'https://dl.fbaipublicfiles.com/fairseq/models/wmt14.en-fr.joined-dict.transformer.tar.bz2',
'transformer.wmt16.en-de': 'https://dl.fbaipublicfiles.com/fairseq/models/wmt16.en-de.joined-dict.transformer.tar.bz2',
'transformer.wmt18.en-de': 'https://dl.fbaipublicfiles.com/fairseq/models/wmt18.en-de.ensemble.tar.gz',
}
def __init__(self, encoder, decoder):
super().__init__(encoder, decoder)
[docs] @staticmethod
def add_args(parser):
"""Add model-specific arguments to the parser."""
# fmt: off
parser.add_argument('--activation-fn',
choices=utils.get_available_activation_fns(),
help='activation function to use')
parser.add_argument('--dropout', type=float, metavar='D',
help='dropout probability')
parser.add_argument('--attention-dropout', type=float, metavar='D',
help='dropout probability for attention weights')
parser.add_argument('--activation-dropout', '--relu-dropout', type=float, metavar='D',
help='dropout probability after activation in FFN.')
parser.add_argument('--encoder-embed-path', type=str, metavar='STR',
help='path to pre-trained encoder embedding')
parser.add_argument('--encoder-embed-dim', type=int, metavar='N',
help='encoder embedding dimension')
parser.add_argument('--encoder-ffn-embed-dim', type=int, metavar='N',
help='encoder embedding dimension for FFN')
parser.add_argument('--encoder-layers', type=int, metavar='N',
help='num encoder layers')
parser.add_argument('--encoder-attention-heads', type=int, metavar='N',
help='num encoder attention heads')
parser.add_argument('--encoder-normalize-before', action='store_true',
help='apply layernorm before each encoder block')
parser.add_argument('--encoder-learned-pos', action='store_true',
help='use learned positional embeddings in the encoder')
parser.add_argument('--decoder-embed-path', type=str, metavar='STR',
help='path to pre-trained decoder embedding')
parser.add_argument('--decoder-embed-dim', type=int, metavar='N',
help='decoder embedding dimension')
parser.add_argument('--decoder-ffn-embed-dim', type=int, metavar='N',
help='decoder embedding dimension for FFN')
parser.add_argument('--decoder-layers', type=int, metavar='N',
help='num decoder layers')
parser.add_argument('--decoder-attention-heads', type=int, metavar='N',
help='num decoder attention heads')
parser.add_argument('--decoder-learned-pos', action='store_true',
help='use learned positional embeddings in the decoder')
parser.add_argument('--decoder-normalize-before', action='store_true',
help='apply layernorm before each decoder block')
parser.add_argument('--share-decoder-input-output-embed', action='store_true',
help='share decoder input and output embeddings')
parser.add_argument('--share-all-embeddings', action='store_true',
help='share encoder, decoder and output embeddings'
' (requires shared dictionary and embed dim)')
parser.add_argument('--no-token-positional-embeddings', default=False, action='store_true',
help='if set, disables positional embeddings (outside self attention)')
parser.add_argument('--adaptive-softmax-cutoff', metavar='EXPR',
help='comma separated list of adaptive softmax cutoff points. '
'Must be used with adaptive_loss criterion'),
parser.add_argument('--adaptive-softmax-dropout', type=float, metavar='D',
help='sets adaptive softmax dropout for the tail projections')
# fmt: on
[docs] @classmethod
def build_model(cls, args, task):
"""Build a new model instance."""
# make sure all arguments are present in older models
base_architecture(args)
if not hasattr(args, 'max_source_positions'):
args.max_source_positions = DEFAULT_MAX_SOURCE_POSITIONS
if not hasattr(args, 'max_target_positions'):
args.max_target_positions = DEFAULT_MAX_TARGET_POSITIONS
src_dict, tgt_dict = task.source_dictionary, task.target_dictionary
def build_embedding(dictionary, embed_dim, path=None):
num_embeddings = len(dictionary)
padding_idx = dictionary.pad()
emb = Embedding(num_embeddings, embed_dim, padding_idx)
# if provided, load from preloaded dictionaries
if path:
embed_dict = utils.parse_embedding(path)
utils.load_embedding(embed_dict, dictionary, emb)
return emb
if args.share_all_embeddings:
if src_dict != tgt_dict:
raise ValueError('--share-all-embeddings requires a joined dictionary')
if args.encoder_embed_dim != args.decoder_embed_dim:
raise ValueError(
'--share-all-embeddings requires --encoder-embed-dim to match --decoder-embed-dim')
if args.decoder_embed_path and (
args.decoder_embed_path != args.encoder_embed_path):
raise ValueError('--share-all-embeddings not compatible with --decoder-embed-path')
encoder_embed_tokens = build_embedding(
src_dict, args.encoder_embed_dim, args.encoder_embed_path
)
decoder_embed_tokens = encoder_embed_tokens
args.share_decoder_input_output_embed = True
else:
encoder_embed_tokens = build_embedding(
src_dict, args.encoder_embed_dim, args.encoder_embed_path
)
decoder_embed_tokens = build_embedding(
tgt_dict, args.decoder_embed_dim, args.decoder_embed_path
)
encoder = cls.build_encoder(args, src_dict, encoder_embed_tokens)
decoder = cls.build_decoder(args, tgt_dict, decoder_embed_tokens)
return TransformerModel(encoder, decoder)
@classmethod
def build_encoder(cls, args, src_dict, embed_tokens):
return TransformerEncoder(args, src_dict, embed_tokens)
@classmethod
def build_decoder(cls, args, tgt_dict, embed_tokens):
return TransformerDecoder(args, tgt_dict, embed_tokens)
[docs]class TransformerEncoder(FairseqEncoder):
"""
Transformer encoder consisting of *args.encoder_layers* layers. Each layer
is a :class:`TransformerEncoderLayer`.
Args:
args (argparse.Namespace): parsed command-line arguments
dictionary (~fairseq.data.Dictionary): encoding dictionary
embed_tokens (torch.nn.Embedding): input embedding
"""
def __init__(self, args, dictionary, embed_tokens):
super().__init__(dictionary)
self.register_buffer('version', torch.Tensor([3]))
self.dropout = args.dropout
embed_dim = embed_tokens.embedding_dim
self.padding_idx = embed_tokens.padding_idx
self.max_source_positions = args.max_source_positions
self.embed_tokens = embed_tokens
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
self.layers = nn.ModuleList([])
self.layers.extend([
TransformerEncoderLayer(args)
for i in range(args.encoder_layers)
])
if args.encoder_normalize_before:
self.layer_norm = LayerNorm(embed_dim)
else:
self.layer_norm = None
[docs] def forward(self, src_tokens, src_lengths):
"""
Args:
src_tokens (LongTensor): tokens in the source language of shape
`(batch, src_len)`
src_lengths (torch.LongTensor): lengths of each source sentence of
shape `(batch)`
Returns:
dict:
- **encoder_out** (Tensor): the last encoder layer's output of
shape `(src_len, batch, embed_dim)`
- **encoder_padding_mask** (ByteTensor): the positions of
padding elements of shape `(batch, src_len)`
"""
# embed tokens and positions
x = self.embed_scale * self.embed_tokens(src_tokens)
if self.embed_positions is not None:
x += self.embed_positions(src_tokens)
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)
if not encoder_padding_mask.any():
encoder_padding_mask = None
# encoder layers
for layer in self.layers:
x = layer(x, encoder_padding_mask)
if self.layer_norm:
x = self.layer_norm(x)
return {
'encoder_out': x, # T x B x C
'encoder_padding_mask': encoder_padding_mask, # B x T
}
[docs] def reorder_encoder_out(self, encoder_out, new_order):
"""
Reorder encoder output according to *new_order*.
Args:
encoder_out: output from the ``forward()`` method
new_order (LongTensor): desired order
Returns:
*encoder_out* rearranged according to *new_order*
"""
if encoder_out['encoder_out'] is not None:
encoder_out['encoder_out'] = \
encoder_out['encoder_out'].index_select(1, new_order)
if encoder_out['encoder_padding_mask'] is not None:
encoder_out['encoder_padding_mask'] = \
encoder_out['encoder_padding_mask'].index_select(0, new_order)
return encoder_out
[docs] def max_positions(self):
"""Maximum input length supported by the encoder."""
if self.embed_positions is None:
return self.max_source_positions
return min(self.max_source_positions, self.embed_positions.max_positions())
[docs] def upgrade_state_dict_named(self, state_dict, name):
"""Upgrade a (possibly old) state dict for new versions of fairseq."""
if isinstance(self.embed_positions, SinusoidalPositionalEmbedding):
weights_key = '{}.embed_positions.weights'.format(name)
if weights_key in state_dict:
del state_dict[weights_key]
state_dict['{}.embed_positions._float_tensor'.format(name)] = torch.FloatTensor(1)
for i in range(len(self.layers)):
# update layer norms
self.layers[i].upgrade_state_dict_named(state_dict, "{}.layers.{}".format(name, i))
version_key = '{}.version'.format(name)
if utils.item(state_dict.get(version_key, torch.Tensor([1]))[0]) < 2:
# earlier checkpoints did not normalize after the stack of layers
self.layer_norm = None
self.normalize = False
state_dict[version_key] = torch.Tensor([1])
return state_dict
[docs]class TransformerDecoder(FairseqIncrementalDecoder):
"""
Transformer decoder consisting of *args.decoder_layers* layers. Each layer
is a :class:`TransformerDecoderLayer`.
Args:
args (argparse.Namespace): parsed command-line arguments
dictionary (~fairseq.data.Dictionary): decoding dictionary
embed_tokens (torch.nn.Embedding): output embedding
no_encoder_attn (bool, optional): whether to attend to encoder outputs
(default: False).
"""
def __init__(self, args, dictionary, embed_tokens, no_encoder_attn=False):
super().__init__(dictionary)
self.register_buffer('version', torch.Tensor([3]))
self.dropout = args.dropout
self.share_input_output_embed = args.share_decoder_input_output_embed
input_embed_dim = embed_tokens.embedding_dim
embed_dim = args.decoder_embed_dim
self.output_embed_dim = args.decoder_output_dim
padding_idx = 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
self.layers = nn.ModuleList([])
self.layers.extend([
TransformerDecoderLayer(args, no_encoder_attn)
for _ in range(args.decoder_layers)
])
self.adaptive_softmax = None
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
if args.adaptive_softmax_cutoff is not None:
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_out = nn.Parameter(torch.Tensor(len(dictionary), self.output_embed_dim))
nn.init.normal_(self.embed_out, 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
[docs] def forward(self, prev_output_tokens, encoder_out=None, incremental_state=None, **unused):
"""
Args:
prev_output_tokens (LongTensor): previous decoder outputs of shape
`(batch, tgt_len)`, for input feeding/teacher forcing
encoder_out (Tensor, optional): output from the encoder, used for
encoder-side attention
incremental_state (dict): dictionary used for storing state during
:ref:`Incremental decoding`
Returns:
tuple:
- the decoder's output of shape `(batch, tgt_len, vocab)`
- a dictionary with any model-specific outputs
"""
x, extra = self.extract_features(prev_output_tokens, encoder_out, incremental_state)
x = self.output_layer(x)
return x, extra
[docs] def extract_features(self, prev_output_tokens, encoder_out=None, incremental_state=None, **unused):
"""
Similar to *forward* but only return features.
Returns:
tuple:
- the decoder's features of shape `(batch, tgt_len, embed_dim)`
- a dictionary with any model-specific outputs
"""
# embed positions
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
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)
attn = None
inner_states = [x]
# decoder layers
for layer in self.layers:
x, attn = layer(
x,
encoder_out['encoder_out'] if encoder_out is not None else None,
encoder_out['encoder_padding_mask'] if encoder_out is not None else None,
incremental_state,
self_attn_mask=self.buffered_future_mask(x) if incremental_state is None else None,
)
inner_states.append(x)
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)
return x, {'attn': attn, 'inner_states': inner_states}
[docs] 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:
return F.linear(features, self.embed_tokens.weight)
else:
return F.linear(features, self.embed_out)
else:
return features
[docs] def max_positions(self):
"""Maximum output length supported by the decoder."""
if self.embed_positions is None:
return self.max_target_positions
return min(self.max_target_positions, self.embed_positions.max_positions())
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 or self._future_mask.size(0) < dim:
self._future_mask = torch.triu(utils.fill_with_neg_inf(tensor.new(dim, dim)), 1)
return self._future_mask[:dim, :dim]
[docs] def upgrade_state_dict_named(self, state_dict, name):
"""Upgrade a (possibly old) state dict for new versions of fairseq."""
if isinstance(self.embed_positions, SinusoidalPositionalEmbedding):
weights_key = '{}.embed_positions.weights'.format(name)
if weights_key in state_dict:
del state_dict[weights_key]
state_dict['{}.embed_positions._float_tensor'.format(name)] = torch.FloatTensor(1)
for i in range(len(self.layers)):
# update layer norms
layer_norm_map = {
'0': 'self_attn_layer_norm',
'1': 'encoder_attn_layer_norm',
'2': 'final_layer_norm'
}
for old, new in layer_norm_map.items():
for m in ('weight', 'bias'):
k = '{}.layers.{}.layer_norms.{}.{}'.format(name, i, old, m)
if k in state_dict:
state_dict['{}.layers.{}.{}.{}'.format(name, i, new, m)] = state_dict[k]
del state_dict[k]
version_key = '{}.version'.format(name)
if utils.item(state_dict.get(version_key, torch.Tensor([1]))[0]) < 2:
# earlier checkpoints did not normalize after the stack of layers
self.layer_norm = None
self.normalize = False
state_dict[version_key] = torch.Tensor([1])
return state_dict
[docs]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)
[docs] 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]
[docs] def forward(self, x, encoder_padding_mask):
"""
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``.
Returns:
encoded output of shape `(seq_len, batch, embed_dim)`
"""
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
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
[docs]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
[docs] def forward(
self,
x,
encoder_out=None,
encoder_padding_mask=None,
incremental_state=None,
prev_self_attn_state=None,
prev_attn_state=None,
self_attn_mask=None,
self_attn_padding_mask=None,
):
"""
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``.
Returns:
encoded output of shape `(seq_len, batch, embed_dim)`
"""
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 self.onnx_trace and incremental_state is not None:
saved_state = self.self_attn._get_input_buffer(incremental_state)
self_attn_state = saved_state["prev_key"], saved_state["prev_value"]
return x, attn, self_attn_state
return x, attn
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.)
return m
@register_model_architecture('transformer', 'transformer')
def base_architecture(args):
args.encoder_embed_path = getattr(args, 'encoder_embed_path', None)
args.encoder_embed_dim = getattr(args, 'encoder_embed_dim', 512)
args.encoder_ffn_embed_dim = getattr(args, 'encoder_ffn_embed_dim', 2048)
args.encoder_layers = getattr(args, 'encoder_layers', 6)
args.encoder_attention_heads = getattr(args, 'encoder_attention_heads', 8)
args.encoder_normalize_before = getattr(args, 'encoder_normalize_before', False)
args.encoder_learned_pos = getattr(args, 'encoder_learned_pos', False)
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', 6)
args.decoder_attention_heads = getattr(args, 'decoder_attention_heads', 8)
args.decoder_normalize_before = getattr(args, 'decoder_normalize_before', False)
args.decoder_learned_pos = getattr(args, 'decoder_learned_pos', False)
args.attention_dropout = getattr(args, 'attention_dropout', 0.)
args.activation_dropout = getattr(args, 'activation_dropout', 0.)
args.activation_fn = getattr(args, 'activation_fn', 'relu')
args.dropout = getattr(args, 'dropout', 0.1)
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', False)
args.share_all_embeddings = getattr(args, 'share_all_embeddings', False)
args.no_token_positional_embeddings = getattr(args, 'no_token_positional_embeddings', False)
args.adaptive_input = getattr(args, 'adaptive_input', False)
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)
@register_model_architecture('transformer', 'transformer_iwslt_de_en')
def transformer_iwslt_de_en(args):
args.encoder_embed_dim = getattr(args, 'encoder_embed_dim', 512)
args.encoder_ffn_embed_dim = getattr(args, 'encoder_ffn_embed_dim', 1024)
args.encoder_attention_heads = getattr(args, 'encoder_attention_heads', 4)
args.encoder_layers = getattr(args, 'encoder_layers', 6)
args.decoder_embed_dim = getattr(args, 'decoder_embed_dim', 512)
args.decoder_ffn_embed_dim = getattr(args, 'decoder_ffn_embed_dim', 1024)
args.decoder_attention_heads = getattr(args, 'decoder_attention_heads', 4)
args.decoder_layers = getattr(args, 'decoder_layers', 6)
base_architecture(args)
@register_model_architecture('transformer', 'transformer_wmt_en_de')
def transformer_wmt_en_de(args):
base_architecture(args)
# parameters used in the "Attention Is All You Need" paper (Vaswani et al., 2017)
@register_model_architecture('transformer', 'transformer_vaswani_wmt_en_de_big')
def transformer_vaswani_wmt_en_de_big(args):
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)
args.encoder_normalize_before = getattr(args, 'encoder_normalize_before', False)
args.decoder_embed_dim = getattr(args, 'decoder_embed_dim', 1024)
args.decoder_ffn_embed_dim = getattr(args, 'decoder_ffn_embed_dim', 4096)
args.decoder_attention_heads = getattr(args, 'decoder_attention_heads', 16)
args.dropout = getattr(args, 'dropout', 0.3)
base_architecture(args)
@register_model_architecture('transformer', 'transformer_vaswani_wmt_en_fr_big')
def transformer_vaswani_wmt_en_fr_big(args):
args.dropout = getattr(args, 'dropout', 0.1)
transformer_vaswani_wmt_en_de_big(args)
@register_model_architecture('transformer', 'transformer_wmt_en_de_big')
def transformer_wmt_en_de_big(args):
args.attention_dropout = getattr(args, 'attention_dropout', 0.1)
transformer_vaswani_wmt_en_de_big(args)
# default parameters used in tensor2tensor implementation
@register_model_architecture('transformer', 'transformer_wmt_en_de_big_t2t')
def transformer_wmt_en_de_big_t2t(args):
args.encoder_normalize_before = getattr(args, 'encoder_normalize_before', True)
args.decoder_normalize_before = getattr(args, 'decoder_normalize_before', True)
args.attention_dropout = getattr(args, 'attention_dropout', 0.1)
args.activation_dropout = getattr(args, 'activation_dropout', 0.1)
transformer_vaswani_wmt_en_de_big(args)