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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.
from typing import Dict, List, NamedTuple, Optional
import torch
import torch.nn as nn
from examples.simultaneous_translation.modules.monotonic_transformer_layer import (
TransformerMonotonicDecoderLayer,
TransformerMonotonicEncoderLayer,
)
from fairseq.models import (
register_model,
register_model_architecture,
)
from fairseq.models.transformer import (
TransformerModel,
TransformerEncoder,
TransformerDecoder,
base_architecture,
transformer_iwslt_de_en,
transformer_vaswani_wmt_en_de_big,
tiny_architecture
)
from torch import Tensor
DEFAULT_MAX_SOURCE_POSITIONS = 1024
DEFAULT_MAX_TARGET_POSITIONS = 1024
READ_ACTION = 0
WRITE_ACTION = 1
TransformerMonotonicDecoderOut = NamedTuple(
"TransformerMonotonicDecoderOut",
[
("action", int),
("p_choose", Optional[Tensor]),
("attn_list", Optional[List[Optional[Dict[str, Tensor]]]]),
("encoder_out", Optional[Dict[str, List[Tensor]]]),
("encoder_padding_mask", Optional[Tensor]),
],
)
@register_model("transformer_unidirectional")
class TransformerUnidirectionalModel(TransformerModel):
@classmethod
def build_encoder(cls, args, src_dict, embed_tokens):
return TransformerMonotonicEncoder(args, src_dict, embed_tokens)
@register_model("transformer_monotonic")
class TransformerModelSimulTrans(TransformerModel):
@classmethod
def build_encoder(cls, args, src_dict, embed_tokens):
return TransformerMonotonicEncoder(args, src_dict, embed_tokens)
@classmethod
def build_decoder(cls, args, tgt_dict, embed_tokens):
return TransformerMonotonicDecoder(args, tgt_dict, embed_tokens)
class TransformerMonotonicEncoder(TransformerEncoder):
def __init__(self, args, dictionary, embed_tokens):
super().__init__(args, dictionary, embed_tokens)
self.dictionary = dictionary
self.layers = nn.ModuleList([])
self.layers.extend(
[
TransformerMonotonicEncoderLayer(args)
for i in range(args.encoder_layers)
]
)
class TransformerMonotonicDecoder(TransformerDecoder):
"""
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__(args, dictionary, embed_tokens, no_encoder_attn=False)
self.dictionary = dictionary
self.layers = nn.ModuleList([])
self.layers.extend(
[
TransformerMonotonicDecoderLayer(args)
for _ in range(args.decoder_layers)
]
)
self.policy_criterion = getattr(args, "policy_criterion", "any")
self.num_updates = None
def set_num_updates(self, num_updates):
self.num_updates = num_updates
def pre_attention(
self,
prev_output_tokens,
encoder_out_dict: Dict[str, List[Tensor]],
incremental_state: Optional[Dict[str, Dict[str, Optional[Tensor]]]] = 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
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 = self.dropout_module(x)
# B x T x C -> T x B x C
x = x.transpose(0, 1)
encoder_out = encoder_out_dict["encoder_out"][0]
if "encoder_padding_mask" in encoder_out_dict:
encoder_padding_mask = (
encoder_out_dict["encoder_padding_mask"][0]
if encoder_out_dict["encoder_padding_mask"]
and len(encoder_out_dict["encoder_padding_mask"]) > 0
else None
)
else:
encoder_padding_mask = None
return x, encoder_out, encoder_padding_mask
def post_attention(self, x):
if self.layer_norm is not None:
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
def clean_cache(
self,
incremental_state: Optional[Dict[str, Dict[str, Optional[Tensor]]]],
end_id: Optional[int] = None,
):
"""
Clean cache in the monotonic layers.
The cache is generated because of a forward pass of decoder has run but no prediction,
so that the self attention key value in decoder is written in the incremental state.
end_id is the last idx of the layers
"""
if end_id is None:
end_id = len(self.layers)
for index, layer in enumerate(self.layers):
if index < end_id:
layer.prune_incremental_state(incremental_state)
def extract_features(
self,
prev_output_tokens,
encoder_out: Optional[Dict[str, List[Tensor]]],
incremental_state: Optional[Dict[str, Dict[str, Optional[Tensor]]]] = None,
full_context_alignment: bool = False, # unused
alignment_layer: Optional[int] = None, # unused
alignment_heads: Optional[int] = None, # unsed
):
"""
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
"""
# incremental_state = None
assert encoder_out is not None
(x, encoder_outs, encoder_padding_mask) = self.pre_attention(
prev_output_tokens, encoder_out, incremental_state
)
attn = None
inner_states = [x]
attn_list: List[Optional[Dict[str, Tensor]]] = []
p_choose = torch.tensor([1.0])
for i, layer in enumerate(self.layers):
x, attn, _ = layer(
x=x,
encoder_out=encoder_outs,
encoder_padding_mask=encoder_padding_mask,
incremental_state=incremental_state,
self_attn_mask=self.buffered_future_mask(x)
if incremental_state is None
else None,
)
inner_states.append(x)
attn_list.append(attn)
if incremental_state is not None:
if_online = incremental_state["online"]["only"]
assert if_online is not None
if if_online.to(torch.bool):
# Online indicates that the encoder states are still changing
assert attn is not None
if self.policy_criterion == "any":
# Any head decide to read than read
head_read = layer.encoder_attn._get_monotonic_buffer(incremental_state)["head_read"]
assert head_read is not None
if head_read.any():
# We need to prune the last self_attn saved_state
# if model decide not to read
# otherwise there will be duplicated saved_state
self.clean_cache(incremental_state, i + 1)
return x, TransformerMonotonicDecoderOut(
action=0,
p_choose=p_choose,
attn_list=None,
encoder_out=None,
encoder_padding_mask=None,
)
x = self.post_attention(x)
return x, TransformerMonotonicDecoderOut(
action=1,
p_choose=p_choose,
attn_list=attn_list,
encoder_out=encoder_out,
encoder_padding_mask=encoder_padding_mask,
)
@register_model_architecture("transformer_monotonic", "transformer_monotonic")
def base_monotonic_architecture(args):
base_architecture(args)
args.encoder_unidirectional = getattr(args, "encoder_unidirectional", False)
@register_model_architecture(
"transformer_monotonic", "transformer_monotonic_iwslt_de_en"
)
def transformer_monotonic_iwslt_de_en(args):
transformer_iwslt_de_en(args)
base_monotonic_architecture(args)
# parameters used in the "Attention Is All You Need" paper (Vaswani et al., 2017)
@register_model_architecture(
"transformer_monotonic", "transformer_monotonic_vaswani_wmt_en_de_big"
)
def transformer_monotonic_vaswani_wmt_en_de_big(args):
transformer_vaswani_wmt_en_de_big(args)
@register_model_architecture(
"transformer_monotonic", "transformer_monotonic_vaswani_wmt_en_fr_big"
)
def transformer_monotonic_vaswani_wmt_en_fr_big(args):
transformer_monotonic_vaswani_wmt_en_fr_big(args)
@register_model_architecture(
"transformer_unidirectional", "transformer_unidirectional_iwslt_de_en"
)
def transformer_unidirectional_iwslt_de_en(args):
transformer_iwslt_de_en(args)
@register_model_architecture("transformer_monotonic", "transformer_monotonic_tiny")
def monotonic_tiny_architecture(args):
tiny_architecture(args)
base_monotonic_architecture(args)
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