chore: import upstream snapshot with attribution
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# Copyright (c) Facebook, Inc. and its affiliates.
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#
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# This source code is licensed under the MIT license found in the
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# LICENSE file in the root directory of this source tree.
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import logging
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import os
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from dataclasses import dataclass, field
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from typing import Optional
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import numpy as np
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import torch
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from fairseq import utils
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from fairseq.data import (
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AppendTokenDataset,
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Dictionary,
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IdDataset,
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LMContextWindowDataset,
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MonolingualDataset,
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NestedDictionaryDataset,
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NumelDataset,
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PadDataset,
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PrependTokenDataset,
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StripTokenDataset,
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TokenBlockDataset,
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TruncatedDictionary,
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data_utils,
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)
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from fairseq.data.indexed_dataset import get_available_dataset_impl
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from fairseq.data.shorten_dataset import maybe_shorten_dataset
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from fairseq.dataclass import ChoiceEnum, FairseqDataclass
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from fairseq.tasks import LegacyFairseqTask, register_task
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from omegaconf import II
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SAMPLE_BREAK_MODE_CHOICES = ChoiceEnum(["none", "complete", "complete_doc", "eos"])
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SHORTEN_METHOD_CHOICES = ChoiceEnum(["none", "truncate", "random_crop"])
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logger = logging.getLogger(__name__)
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@dataclass
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class LanguageModelingConfig(FairseqDataclass):
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data: Optional[str] = field(
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default=None, metadata={"help": "path to data directory"}
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)
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sample_break_mode: SAMPLE_BREAK_MODE_CHOICES = field(
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default="none",
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metadata={
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"help": 'If omitted or "none", fills each sample with tokens-per-sample '
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'tokens. If set to "complete", splits samples only at the end '
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"of sentence, but may include multiple sentences per sample. "
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'"complete_doc" is similar but respects doc boundaries. '
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'If set to "eos", includes only one sentence per sample.'
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},
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)
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tokens_per_sample: int = field(
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default=1024,
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metadata={"help": "max number of tokens per sample for LM dataset"},
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)
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output_dictionary_size: int = field(
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default=-1, metadata={"help": "limit the size of output dictionary"}
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)
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self_target: bool = field(default=False, metadata={"help": "include self target"})
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future_target: bool = field(
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default=False, metadata={"help": "include future target"}
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)
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past_target: bool = field(default=False, metadata={"help": "include past target"})
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add_bos_token: bool = field(
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default=False, metadata={"help": "prepend beginning of sentence token (<s>)"}
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)
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max_target_positions: Optional[int] = field(
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default=None, metadata={"help": "max number of tokens in the target sequence"}
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)
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shorten_method: SHORTEN_METHOD_CHOICES = field(
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default="none",
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metadata={
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"help": "if not none, shorten sequences that exceed --tokens-per-sample"
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},
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)
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shorten_data_split_list: str = field(
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default="",
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metadata={
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"help": "comma-separated list of dataset splits to apply shortening to, "
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'e.g., "train,valid" (default: all dataset splits)'
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},
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)
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# TODO common vars below add to parent
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seed: int = II("common.seed")
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dataset_impl: Optional[ChoiceEnum(get_available_dataset_impl())] = II(
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"dataset.dataset_impl"
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)
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data_buffer_size: int = II("dataset.data_buffer_size")
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tpu: bool = II("common.tpu")
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@register_task("language_modeling", dataclass=LanguageModelingConfig)
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class LanguageModelingTask(LegacyFairseqTask):
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"""
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Train a language model.
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Args:
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dictionary (~fairseq.data.Dictionary): the dictionary for the input of
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the language model
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output_dictionary (~fairseq.data.Dictionary): the dictionary for the
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output of the language model. In most cases it will be the same as
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*dictionary*, but could possibly be a more limited version of the
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dictionary (if ``--output-dictionary-size`` is used).
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targets (List[str]): list of the target types that the language model
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should predict. Can be one of "self", "future", and "past".
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Defaults to "future".
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.. note::
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The language modeling task is compatible with :mod:`fairseq-train`,
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:mod:`fairseq-generate`, :mod:`fairseq-interactive` and
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:mod:`fairseq-eval-lm`.
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The language modeling task provides the following additional command-line
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arguments:
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.. argparse::
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:ref: fairseq.tasks.language_modeling_parser
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:prog:
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"""
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def __init__(self, args, dictionary, output_dictionary=None, targets=None):
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super().__init__(args)
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self.dictionary = dictionary
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self.output_dictionary = output_dictionary or dictionary
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if targets is None:
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targets = ["future"]
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self.targets = targets
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@classmethod
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def setup_dictionary(cls, args, **kwargs):
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dictionary = None
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output_dictionary = None
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if args.data:
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paths = utils.split_paths(args.data)
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assert len(paths) > 0
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dictionary = Dictionary.load(os.path.join(paths[0], "dict.txt"))
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logger.info("dictionary: {} types".format(len(dictionary)))
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output_dictionary = dictionary
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if args.output_dictionary_size >= 0:
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output_dictionary = TruncatedDictionary(
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dictionary, args.output_dictionary_size
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)
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return (dictionary, output_dictionary)
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@classmethod
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def setup_task(cls, args, **kwargs):
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"""Setup the task (e.g., load dictionaries).
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Args:
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args (argparse.Namespace): parsed command-line arguments
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"""
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dictionary, output_dictionary = cls.setup_dictionary(args, **kwargs)
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# upgrade old checkpoints
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if getattr(args, "exclude_self_target", False):
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args.self_target = False
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targets = []
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if getattr(args, "self_target", False):
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targets.append("self")
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if getattr(args, "future_target", False):
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targets.append("future")
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if getattr(args, "past_target", False):
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targets.append("past")
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if len(targets) == 0:
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# standard language modeling
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targets = ["future"]
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return cls(args, dictionary, output_dictionary, targets=targets)
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def build_model(self, args):
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model = super().build_model(args)
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for target in self.targets:
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if target not in model.supported_targets:
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raise ValueError(
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"Unsupported language modeling target: {}".format(target)
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)
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return model
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def load_dataset(
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self, split: str, epoch=1, combine=False, **kwargs
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) -> MonolingualDataset:
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"""Load a given dataset split.
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Args:
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split (str): name of the split (e.g., train, valid, test)
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"""
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paths = utils.split_paths(self.args.data)
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assert len(paths) > 0
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data_path = paths[(epoch - 1) % len(paths)]
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split_path = os.path.join(data_path, split)
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dataset = data_utils.load_indexed_dataset(
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split_path, self.dictionary, self.args.dataset_impl, combine=combine
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)
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if dataset is None:
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raise FileNotFoundError(
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"Dataset not found: {} ({})".format(split, split_path)
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)
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dataset = maybe_shorten_dataset(
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dataset,
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split,
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self.args.shorten_data_split_list,
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self.args.shorten_method,
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self.args.tokens_per_sample,
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self.args.seed,
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)
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dataset = TokenBlockDataset(
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dataset,
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dataset.sizes,
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self.args.tokens_per_sample,
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pad=self.dictionary.pad(),
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eos=self.dictionary.eos(),
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break_mode=self.args.sample_break_mode,
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include_targets=True,
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)
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add_eos_for_other_targets = (
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self.args.sample_break_mode is not None
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and self.args.sample_break_mode != "none"
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)
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self.datasets[split] = MonolingualDataset(
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dataset=dataset,
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sizes=dataset.sizes,
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src_vocab=self.dictionary,
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tgt_vocab=self.output_dictionary,
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add_eos_for_other_targets=add_eos_for_other_targets,
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shuffle=True,
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targets=self.targets,
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add_bos_token=self.args.add_bos_token,
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)
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def build_dataset_for_inference(self, src_tokens, src_lengths, **kwargs):
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"""
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Generate batches for inference. We prepend an eos token to src_tokens
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(or bos if `--add-bos-token` is set) and we append a <pad> to target.
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This is convenient both for generation with a prefix and LM scoring.
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"""
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dataset = StripTokenDataset(
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TokenBlockDataset(
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src_tokens,
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src_lengths,
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block_size=None, # ignored for "eos" break mode
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pad=self.source_dictionary.pad(),
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eos=self.source_dictionary.eos(),
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break_mode="eos",
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),
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# remove eos from (end of) target sequence
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self.source_dictionary.eos(),
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)
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src_dataset = PrependTokenDataset(
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dataset,
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token=(
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self.source_dictionary.bos()
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if getattr(self.args, "add_bos_token", False)
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else self.source_dictionary.eos()
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),
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)
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tgt_dataset = AppendTokenDataset(dataset, token=self.source_dictionary.pad())
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return NestedDictionaryDataset(
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{
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"id": IdDataset(),
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"net_input": {
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"src_tokens": PadDataset(
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src_dataset,
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pad_idx=self.source_dictionary.pad(),
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left_pad=False,
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),
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"src_lengths": NumelDataset(src_dataset, reduce=False),
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},
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"target": PadDataset(
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tgt_dataset, pad_idx=self.source_dictionary.pad(), left_pad=False
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),
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},
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sizes=[np.array(src_lengths)],
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)
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def inference_step(
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self, generator, models, sample, prefix_tokens=None, constraints=None
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):
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with torch.no_grad():
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# Generation will always be conditioned on bos_token
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if getattr(self.args, "add_bos_token", False):
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bos_token = self.source_dictionary.bos()
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else:
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bos_token = self.source_dictionary.eos()
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if constraints is not None:
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raise NotImplementedError(
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"Constrained decoding with the language_modeling task is not supported"
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)
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# SequenceGenerator doesn't use src_tokens directly, we need to
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# pass the `prefix_tokens` argument instead
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if prefix_tokens is None and sample["net_input"]["src_tokens"].nelement():
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prefix_tokens = sample["net_input"]["src_tokens"]
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if prefix_tokens[:, 0].eq(bos_token).all():
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prefix_tokens = prefix_tokens[:, 1:]
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return generator.generate(
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models, sample, prefix_tokens=prefix_tokens, bos_token=bos_token
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)
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def eval_lm_dataloader(
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self,
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dataset,
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max_tokens: Optional[int] = 36000,
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batch_size: Optional[int] = None,
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max_positions: Optional[int] = None,
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num_shards: int = 1,
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shard_id: int = 0,
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num_workers: int = 1,
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data_buffer_size: int = 10,
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# ensures that every evaluated token has access to a context of at least
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# this size, if possible
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context_window: int = 0,
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):
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if context_window > 0:
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dataset = LMContextWindowDataset(
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dataset=dataset,
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tokens_per_sample=self.args.tokens_per_sample,
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context_window=context_window,
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pad_idx=self.source_dictionary.pad(),
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)
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return self.get_batch_iterator(
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dataset=dataset,
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max_tokens=max_tokens,
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max_sentences=batch_size,
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max_positions=max_positions,
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ignore_invalid_inputs=True,
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num_shards=num_shards,
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shard_id=shard_id,
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num_workers=num_workers,
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data_buffer_size=data_buffer_size,
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).next_epoch_itr(shuffle=False)
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@property
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def source_dictionary(self):
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"""Return the :class:`~fairseq.data.Dictionary` for the language
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model."""
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return self.dictionary
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@property
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def target_dictionary(self):
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"""Return the :class:`~fairseq.data.Dictionary` for the language
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model."""
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return self.output_dictionary
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