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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.
import logging
from dataclasses import dataclass
from typing import Dict, List, Optional
import torch
from fairseq.dataclass import FairseqDataclass
from fairseq.models import (
FairseqIncrementalDecoder,
FairseqLanguageModel,
register_model,
)
from .adaptive_span_model import TransformerSeq as AdaptiveSpanTransformerModel
logger = logging.getLogger(__name__)
@dataclass
class AdaptiveSpanSmallConfig(FairseqDataclass):
# defaults come from https://github.com/facebookresearch/adaptive-span/blob/master/experiments/enwik8_small.sh
vocab_size: int = 50
d_model: int = 256
n_head: int = 4
d_inner: int = 1024
n_layer: int = 8
attn_span: int = 1024
dropout: float = 0.0
emb_dropout: float = 0.0
adapt_span_ramp: int = 32
adapt_span_init: float = 0.0
aux_loss_scaler: float = 0.000002
adapt_span_layer: bool = False
@register_model("adaptive_span", dataclass=AdaptiveSpanSmallConfig)
class AdaptiveSpanTransformer(FairseqLanguageModel):
@classmethod
def build_model(cls, cfg: AdaptiveSpanSmallConfig, task):
return cls(AdaptiveSpanDecoder(cfg, task))
def get_aux_loss(self):
return self.decoder.get_aux_loss()
def get_current_max_span(self):
return self.decoder.get_current_max_span()
def get_current_avg_span(self):
return self.decoder.get_current_avg_span()
class AdaptiveSpanDecoder(FairseqIncrementalDecoder):
def __init__(self, cfg, task):
super().__init__(task.target_dictionary)
self.config = cfg
config = AdaptiveSpanSmallConfig(
vocab_size=len(task.target_dictionary),
d_model=cfg.d_model,
n_head=cfg.n_head,
d_inner=cfg.d_inner,
n_layer=cfg.n_layer,
attn_span=cfg.attn_span,
dropout=cfg.dropout,
emb_dropout=cfg.emb_dropout,
adapt_span_ramp=cfg.adapt_span_ramp,
adapt_span_init=cfg.adapt_span_init,
aux_loss_scaler=cfg.aux_loss_scaler,
adapt_span_layer=cfg.adapt_span_layer,
)
logger.info(config)
self.model = AdaptiveSpanTransformerModel(**config.__dict__)
self._mems = None
def forward(
self,
src_tokens,
incremental_state: Optional[Dict[str, List[torch.Tensor]]] = None,
encoder_out=None,
):
bsz = src_tokens.size(0)
if incremental_state is not None: # used during inference
mems = self.get_incremental_state("mems")
src_tokens = src_tokens[:, -1:] # only keep the most recent token
else:
mems = self._mems
if mems is None:
# first time init
mems = self.init_hid_cache(bsz)
output = self.model(x=src_tokens, h_cache=mems,)
if incremental_state is not None:
self.set_incremental_state(incremental_state, "mems", output[1])
else:
self._mems = output[1]
return (output[0],)
def max_positions(self):
return self.config.attn_span
def init_hid_cache(self, batch_sz):
hid = []
for layer in self.model.layers:
param = next(self.model.parameters())
h = torch.zeros(
batch_sz,
layer.get_cache_size(),
self.config.d_model,
dtype=param.dtype,
device=param.device,
)
hid.append(h)
return hid
def get_aux_loss(self):
return self.model.get_aux_loss()
def get_current_max_span(self):
return self.model.get_current_max_span()
def get_current_avg_span(self):
return self.model.get_current_avg_span()
def reorder_incremental_state(
self,
incremental_state: Dict[str, Dict[str, Optional[torch.Tensor]]],
new_order: torch.Tensor,
):
"""Reorder incremental state.
This will be called when the order of the input has changed from the
previous time step. A typical use case is beam search, where the input
order changes between time steps based on the selection of beams.
"""
raise NotImplementedError("This is required for generation/beam search")
# mems = self.get_incremental_state(incremental_state, "mems")
# if mems is not None:
# new_mems = [mems_i.index_select(1, new_order) for mems_i in mems]
# self.set_incremental_state(incremental_state, "mems", new_mems)
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