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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 argparse
import torch
from fairseq import utils
from fairseq.data import Dictionary
from fairseq.data.language_pair_dataset import collate
from fairseq.models import (
FairseqEncoder,
FairseqEncoderDecoderModel,
FairseqIncrementalDecoder,
)
from fairseq.tasks import FairseqTask
def dummy_dictionary(vocab_size, prefix='token_'):
d = Dictionary()
for i in range(vocab_size):
token = prefix + str(i)
d.add_symbol(token)
d.finalize(padding_factor=1) # don't add extra padding symbols
return d
def dummy_dataloader(
samples,
padding_idx=1,
eos_idx=2,
batch_size=None,
):
if batch_size is None:
batch_size = len(samples)
# add any missing data to samples
for i, sample in enumerate(samples):
if 'id' not in sample:
sample['id'] = i
# create dataloader
dataset = TestDataset(samples)
dataloader = torch.utils.data.DataLoader(
dataset,
batch_size=batch_size,
collate_fn=(lambda samples: collate(samples, padding_idx, eos_idx)),
)
return iter(dataloader)
def sequence_generator_setup():
# construct dummy dictionary
d = dummy_dictionary(vocab_size=2)
eos = d.eos()
w1 = 4
w2 = 5
# construct source data
src_tokens = torch.LongTensor([[w1, w2, eos], [w1, w2, eos]])
src_lengths = torch.LongTensor([2, 2])
args = argparse.Namespace()
unk = 0.
args.beam_probs = [
# step 0:
torch.FloatTensor([
# eos w1 w2
# sentence 1:
[0.0, unk, 0.9, 0.1], # beam 1
[0.0, unk, 0.9, 0.1], # beam 2
# sentence 2:
[0.0, unk, 0.7, 0.3],
[0.0, unk, 0.7, 0.3],
]),
# step 1:
torch.FloatTensor([
# eos w1 w2 prefix
# sentence 1:
[1.0, unk, 0.0, 0.0], # w1: 0.9 (emit: w1 <eos>: 0.9*1.0)
[0.0, unk, 0.9, 0.1], # w2: 0.1
# sentence 2:
[0.25, unk, 0.35, 0.4], # w1: 0.7 (don't emit: w1 <eos>: 0.7*0.25)
[0.00, unk, 0.10, 0.9], # w2: 0.3
]),
# step 2:
torch.FloatTensor([
# eos w1 w2 prefix
# sentence 1:
[0.0, unk, 0.1, 0.9], # w2 w1: 0.1*0.9
[0.6, unk, 0.2, 0.2], # w2 w2: 0.1*0.1 (emit: w2 w2 <eos>: 0.1*0.1*0.6)
# sentence 2:
[0.60, unk, 0.4, 0.00], # w1 w2: 0.7*0.4 (emit: w1 w2 <eos>: 0.7*0.4*0.6)
[0.01, unk, 0.0, 0.99], # w2 w2: 0.3*0.9
]),
# step 3:
torch.FloatTensor([
# eos w1 w2 prefix
# sentence 1:
[1.0, unk, 0.0, 0.0], # w2 w1 w2: 0.1*0.9*0.9 (emit: w2 w1 w2 <eos>: 0.1*0.9*0.9*1.0)
[1.0, unk, 0.0, 0.0], # w2 w1 w1: 0.1*0.9*0.1 (emit: w2 w1 w1 <eos>: 0.1*0.9*0.1*1.0)
# sentence 2:
[0.1, unk, 0.5, 0.4], # w2 w2 w2: 0.3*0.9*0.99 (emit: w2 w2 w2 <eos>: 0.3*0.9*0.99*0.1)
[1.0, unk, 0.0, 0.0], # w1 w2 w1: 0.7*0.4*0.4 (emit: w1 w2 w1 <eos>: 0.7*0.4*0.4*1.0)
]),
]
task = TestTranslationTask.setup_task(args, d, d)
model = task.build_model(args)
tgt_dict = task.target_dictionary
return tgt_dict, w1, w2, src_tokens, src_lengths, model
class TestDataset(torch.utils.data.Dataset):
def __init__(self, data):
super().__init__()
self.data = data
self.sizes = None
def __getitem__(self, index):
return self.data[index]
def __len__(self):
return len(self.data)
class TestTranslationTask(FairseqTask):
def __init__(self, args, src_dict, tgt_dict, model):
super().__init__(args)
self.src_dict = src_dict
self.tgt_dict = tgt_dict
self.model = model
@classmethod
def setup_task(cls, args, src_dict=None, tgt_dict=None, model=None):
return cls(args, src_dict, tgt_dict, model)
def build_model(self, args):
return TestModel.build_model(args, self)
@property
def source_dictionary(self):
return self.src_dict
@property
def target_dictionary(self):
return self.tgt_dict
class TestModel(FairseqEncoderDecoderModel):
def __init__(self, encoder, decoder):
super().__init__(encoder, decoder)
@classmethod
def build_model(cls, args, task):
encoder = TestEncoder(args, task.source_dictionary)
decoder = TestIncrementalDecoder(args, task.target_dictionary)
return cls(encoder, decoder)
class TestEncoder(FairseqEncoder):
def __init__(self, args, dictionary):
super().__init__(dictionary)
self.args = args
def forward(self, src_tokens, src_lengths=None, **kwargs):
return src_tokens
def reorder_encoder_out(self, encoder_out, new_order):
return encoder_out.index_select(0, new_order)
class TestIncrementalDecoder(FairseqIncrementalDecoder):
def __init__(self, args, dictionary):
super().__init__(dictionary)
assert hasattr(args, 'beam_probs') or hasattr(args, 'probs')
args.max_decoder_positions = getattr(args, 'max_decoder_positions', 100)
self.args = args
def forward(self, prev_output_tokens, encoder_out=None, incremental_state=None):
if incremental_state is not None:
prev_output_tokens = prev_output_tokens[:, -1:]
bbsz = prev_output_tokens.size(0)
vocab = len(self.dictionary)
src_len = encoder_out.size(1)
tgt_len = prev_output_tokens.size(1)
# determine number of steps
if incremental_state is not None:
# cache step number
step = utils.get_incremental_state(self, incremental_state, 'step')
if step is None:
step = 0
utils.set_incremental_state(self, incremental_state, 'step', step + 1)
steps = [step]
else:
steps = list(range(tgt_len))
# define output in terms of raw probs
if hasattr(self.args, 'probs'):
assert self.args.probs.dim() == 3, \
'expected probs to have size bsz*steps*vocab'
probs = self.args.probs.index_select(1, torch.LongTensor(steps))
else:
probs = torch.FloatTensor(bbsz, len(steps), vocab).zero_()
for i, step in enumerate(steps):
# args.beam_probs gives the probability for every vocab element,
# starting with eos, then unknown, and then the rest of the vocab
if step < len(self.args.beam_probs):
probs[:, i, self.dictionary.eos():] = self.args.beam_probs[step]
else:
probs[:, i, self.dictionary.eos()] = 1.0
# random attention
attn = torch.rand(bbsz, tgt_len, src_len)
dev = prev_output_tokens.device
return probs.to(dev), attn.to(dev)
def get_normalized_probs(self, net_output, log_probs, _):
# the decoder returns probabilities directly
probs = net_output[0]
if log_probs:
return probs.log()
else:
return probs
def max_positions(self):
return self.args.max_decoder_positions
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