File size: 7,111 Bytes
85ba398 |
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 |
# 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, Optional, Tuple
import torch
import torch.nn as nn
from torch import Tensor
import logging
from fairseq import utils
from fairseq.dataclass.utils import gen_parser_from_dataclass
from fairseq.distributed import fsdp_wrap
from fairseq.models import FairseqEncoderDecoderModel
from fairseq.models.transformer import (
TransformerConfig,
TransformerDecoderBase,
TransformerEncoderBase,
)
logger = logging.getLogger(__name__)
class TransformerModelBase(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:
"""
def __init__(self, cfg, encoder, decoder):
super().__init__(encoder, decoder)
self.cfg = cfg
self.supports_align_args = True
@classmethod
def add_args(cls, parser):
"""Add model-specific arguments to the parser."""
# we want to build the args recursively in this case.
gen_parser_from_dataclass(
parser, TransformerConfig(), delete_default=False, with_prefix=""
)
@classmethod
def build_model(cls, cfg, task):
"""Build a new model instance."""
# -- TODO T96535332
# bug caused by interaction between OmegaConf II and argparsing
cfg.decoder.input_dim = int(cfg.decoder.input_dim)
cfg.decoder.output_dim = int(cfg.decoder.output_dim)
# --
if cfg.encoder.layers_to_keep:
cfg.encoder.layers = len(cfg.encoder.layers_to_keep.split(","))
if cfg.decoder.layers_to_keep:
cfg.decoder.layers = len(cfg.decoder.layers_to_keep.split(","))
src_dict, tgt_dict = task.source_dictionary, task.target_dictionary
if cfg.share_all_embeddings:
if src_dict != tgt_dict:
raise ValueError("--share-all-embeddings requires a joined dictionary")
if cfg.encoder.embed_dim != cfg.decoder.embed_dim:
raise ValueError(
"--share-all-embeddings requires --encoder-embed-dim to match --decoder-embed-dim"
)
if cfg.decoder.embed_path and (
cfg.decoder.embed_path != cfg.encoder.embed_path
):
raise ValueError(
"--share-all-embeddings not compatible with --decoder-embed-path"
)
encoder_embed_tokens = cls.build_embedding(
cfg, src_dict, cfg.encoder.embed_dim, cfg.encoder.embed_path
)
decoder_embed_tokens = encoder_embed_tokens
cfg.share_decoder_input_output_embed = True
elif cfg.merge_src_tgt_embed:
logger.info(f"source dict size: {len(src_dict)}")
logger.info(f"target dict size: {len(tgt_dict)}")
src_dict.update(tgt_dict)
task.src_dict = src_dict
task.tgt_dict = src_dict
logger.info(f"merged dict size: {len(src_dict)}")
encoder_embed_tokens = cls.build_embedding(
cfg, src_dict, cfg.encoder.embed_dim
)
decoder_embed_tokens = encoder_embed_tokens
cfg.share_decoder_input_output_embed = True
else:
encoder_embed_tokens = cls.build_embedding(
cfg, src_dict, cfg.encoder.embed_dim, cfg.encoder.embed_path
)
decoder_embed_tokens = cls.build_embedding(
cfg, tgt_dict, cfg.decoder.embed_dim, cfg.decoder.embed_path
)
if cfg.offload_activations:
cfg.checkpoint_activations = True # offloading implies checkpointing
encoder = cls.build_encoder(cfg, src_dict, encoder_embed_tokens)
decoder = cls.build_decoder(cfg, tgt_dict, decoder_embed_tokens)
return cls(cfg, encoder, decoder)
@classmethod
def build_embedding(cls, cfg, 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
@classmethod
def build_encoder(cls, cfg, src_dict, embed_tokens):
return TransformerEncoderBase(cfg, src_dict, embed_tokens)
@classmethod
def build_decoder(cls, cfg, tgt_dict, embed_tokens):
return TransformerDecoderBase(
cfg,
tgt_dict,
embed_tokens,
no_encoder_attn=cfg.no_cross_attention,
)
# TorchScript doesn't support optional arguments with variable length (**kwargs).
# Current workaround is to add union of all arguments in child classes.
def forward(
self,
src_tokens,
src_lengths,
prev_output_tokens,
return_all_hiddens: bool = True,
features_only: bool = False,
alignment_layer: Optional[int] = None,
alignment_heads: Optional[int] = None,
):
"""
Run the forward pass for an encoder-decoder model.
Copied from the base class, but without ``**kwargs``,
which are not supported by TorchScript.
"""
encoder_out = self.encoder(
src_tokens, src_lengths=src_lengths, return_all_hiddens=return_all_hiddens
)
decoder_out = 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,
)
return decoder_out
# Since get_normalized_probs is in the Fairseq Model which is not scriptable,
# I rewrite the get_normalized_probs from Base Class to call the
# helper function in the Base Class.
@torch.jit.export
def get_normalized_probs(
self,
net_output: Tuple[Tensor, Optional[Dict[str, List[Optional[Tensor]]]]],
log_probs: bool,
sample: Optional[Dict[str, Tensor]] = None,
):
"""Get normalized probabilities (or log probs) from a net's output."""
return self.get_normalized_probs_scriptable(net_output, log_probs, sample)
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
|