Source code for fairseq.tasks.fairseq_task

# 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
import os
import warnings
from argparse import Namespace

import torch
from fairseq import metrics, search, tokenizer, utils
from import Dictionary, FairseqDataset, data_utils, encoders, iterators
from fairseq.dataclass import FairseqDataclass
from fairseq.dataclass.utils import gen_parser_from_dataclass
from omegaconf import DictConfig

logger = logging.getLogger(__name__)

[docs]class FairseqTask(object): """ Tasks store dictionaries and provide helpers for loading/iterating over Datasets, initializing the Model/Criterion and calculating the loss. """
[docs] @classmethod def add_args(cls, parser): """Add task-specific arguments to the parser.""" dc = getattr(cls, "__dataclass", None) if dc is not None: gen_parser_from_dataclass(parser, dc())
[docs] @staticmethod def logging_outputs_can_be_summed(criterion) -> bool: """ Whether the logging outputs returned by `train_step` and `valid_step` can be summed across workers prior to calling `aggregate_logging_outputs`. Setting this to True will improves distributed training speed. """ return criterion.logging_outputs_can_be_summed()
def __init__(self, cfg: FairseqDataclass, **kwargs): self.cfg = cfg self.datasets = {} self.dataset_to_epoch_iter = {}
[docs] @classmethod def load_dictionary(cls, filename): """Load the dictionary from the filename Args: filename (str): the filename """ return Dictionary.load(filename)
[docs] @classmethod def build_dictionary( cls, filenames, workers=1, threshold=-1, nwords=-1, padding_factor=8 ): """Build the dictionary Args: filenames (list): list of filenames workers (int): number of concurrent workers threshold (int): defines the minimum word count nwords (int): defines the total number of words in the final dictionary, including special symbols padding_factor (int): can be used to pad the dictionary size to be a multiple of 8, which is important on some hardware (e.g., Nvidia Tensor Cores). """ d = Dictionary() for filename in filenames: Dictionary.add_file_to_dictionary( filename, d, tokenizer.tokenize_line, workers ) d.finalize(threshold=threshold, nwords=nwords, padding_factor=padding_factor) return d
[docs] @classmethod def setup_task(cls, cfg: DictConfig, **kwargs): """Setup the task (e.g., load dictionaries). Args: cfg (omegaconf.DictConfig): parsed command-line arguments """ return cls(cfg, **kwargs)
[docs] def has_sharded_data(self, split): return os.pathsep in getattr(self.cfg, "data", "")
[docs] def load_dataset( self, split: str, combine: bool = False, task_cfg: FairseqDataclass = None, **kwargs ): """Load a given dataset split. Args: split (str): name of the split (e.g., train, valid, test) combine (bool): combines a split segmented into pieces into one dataset task_cfg (FairseqDataclass): optional task configuration stored in the checkpoint that can be used to load datasets """ raise NotImplementedError
[docs] def dataset(self, split): """ Return a loaded dataset split. Args: split (str): name of the split (e.g., train, valid, test) Returns: a :class:`` corresponding to *split* """ from import FairseqDataset if split not in self.datasets: raise KeyError("Dataset not loaded: " + split) if not isinstance(self.datasets[split], FairseqDataset): raise TypeError("Datasets are expected to be of type FairseqDataset") return self.datasets[split]
[docs] def filter_indices_by_size( self, indices, dataset, max_positions=None, ignore_invalid_inputs=False ): """ Filter examples that are too large Args: indices (np.array): original array of sample indices dataset ( dataset to batch max_positions (optional): max sentence length supported by the model (default: None). ignore_invalid_inputs (bool, optional): don't raise Exception for sentences that are too long (default: False). Returns: np.array: array of filtered sample indices """ indices, ignored = dataset.filter_indices_by_size(indices, max_positions) if len(ignored) > 0: if not ignore_invalid_inputs: raise Exception( ( "Size of sample #{} is invalid (={}) since max_positions={}, " "skip this example with --skip-invalid-size-inputs-valid-test" ).format(ignored[0], dataset.size(ignored[0]), max_positions) ) logger.warning( ( "{} samples have invalid sizes and will be skipped, " "max_positions={}, first few sample ids={}" ).format(len(ignored), max_positions, ignored[:10]) ) return indices
[docs] def can_reuse_epoch_itr(self, dataset): # We can reuse the epoch iterator across epochs as long as the dataset # hasn't disabled it. We default to ``False`` here, although in practice # this will be ``True`` for most datasets that inherit from # ``FairseqDataset`` due to the base implementation there. return getattr(dataset, "can_reuse_epoch_itr_across_epochs", False)
[docs] def get_batch_iterator( self, dataset, max_tokens=None, max_sentences=None, max_positions=None, ignore_invalid_inputs=False, required_batch_size_multiple=1, seed=1, num_shards=1, shard_id=0, num_workers=0, epoch=1, data_buffer_size=0, disable_iterator_cache=False, ): """ Get an iterator that yields batches of data from the given dataset. Args: dataset ( dataset to batch max_tokens (int, optional): max number of tokens in each batch (default: None). max_sentences (int, optional): max number of sentences in each batch (default: None). max_positions (optional): max sentence length supported by the model (default: None). ignore_invalid_inputs (bool, optional): don't raise Exception for sentences that are too long (default: False). required_batch_size_multiple (int, optional): require batch size to be a multiple of N (default: 1). seed (int, optional): seed for random number generator for reproducibility (default: 1). num_shards (int, optional): shard the data iterator into N shards (default: 1). shard_id (int, optional): which shard of the data iterator to return (default: 0). num_workers (int, optional): how many subprocesses to use for data loading. 0 means the data will be loaded in the main process (default: 0). epoch (int, optional): the epoch to start the iterator from (default: 1). data_buffer_size (int, optional): number of batches to preload (default: 0). disable_iterator_cache (bool, optional): don't cache the EpochBatchIterator (ignores `FairseqTask::can_reuse_epoch_itr`) (default: False). Returns: ~fairseq.iterators.EpochBatchIterator: a batched iterator over the given dataset split """ can_reuse_epoch_itr = not disable_iterator_cache and self.can_reuse_epoch_itr( dataset ) if can_reuse_epoch_itr and dataset in self.dataset_to_epoch_iter: logger.debug("reusing EpochBatchIterator for epoch {}".format(epoch)) return self.dataset_to_epoch_iter[dataset] assert isinstance(dataset, FairseqDataset) # initialize the dataset with the correct starting epoch dataset.set_epoch(epoch) # get indices ordered by example size with data_utils.numpy_seed(seed): indices = dataset.ordered_indices() # filter examples that are too large if max_positions is not None: indices = self.filter_indices_by_size( indices, dataset, max_positions, ignore_invalid_inputs ) # create mini-batches with given size constraints batch_sampler = dataset.batch_by_size( indices, max_tokens=max_tokens, max_sentences=max_sentences, required_batch_size_multiple=required_batch_size_multiple, ) # return a reusable, sharded iterator epoch_iter = iterators.EpochBatchIterator( dataset=dataset, collate_fn=dataset.collater, batch_sampler=batch_sampler, seed=seed, num_shards=num_shards, shard_id=shard_id, num_workers=num_workers, epoch=epoch, buffer_size=data_buffer_size, ) if can_reuse_epoch_itr: self.dataset_to_epoch_iter[dataset] = epoch_iter return epoch_iter
[docs] def build_model(self, cfg: FairseqDataclass): """ Build the :class:`~fairseq.models.BaseFairseqModel` instance for this task. Args: cfg (FairseqDataclass): configuration object Returns: a :class:`~fairseq.models.BaseFairseqModel` instance """ from fairseq import models, quantization_utils model = models.build_model(cfg, self) if getattr(cfg, "tpu", False): model.prepare_for_tpu_() model = quantization_utils.quantize_model_scalar(model, cfg) return model
[docs] def build_criterion(self, cfg: DictConfig): """ Build the :class:`~fairseq.criterions.FairseqCriterion` instance for this task. Args: cfg (omegaconf.DictConfig): configration object Returns: a :class:`~fairseq.criterions.FairseqCriterion` instance """ from fairseq import criterions return criterions.build_criterion(cfg, self)
[docs] def build_generator( self, models, args, seq_gen_cls=None, extra_gen_cls_kwargs=None ): if getattr(args, "score_reference", False): from fairseq.sequence_scorer import SequenceScorer return SequenceScorer( self.target_dictionary, compute_alignment=getattr(args, "print_alignment", False), ) from fairseq.sequence_generator import ( SequenceGenerator, SequenceGeneratorWithAlignment, ) # Choose search strategy. Defaults to Beam Search. sampling = getattr(args, "sampling", False) sampling_topk = getattr(args, "sampling_topk", -1) sampling_topp = getattr(args, "sampling_topp", -1.0) diverse_beam_groups = getattr(args, "diverse_beam_groups", -1) diverse_beam_strength = getattr(args, "diverse_beam_strength", 0.5) match_source_len = getattr(args, "match_source_len", False) diversity_rate = getattr(args, "diversity_rate", -1) constrained = getattr(args, "constraints", False) prefix_allowed_tokens_fn = getattr(args, "prefix_allowed_tokens_fn", None) if ( sum( int(cond) for cond in [ sampling, diverse_beam_groups > 0, match_source_len, diversity_rate > 0, ] ) > 1 ): raise ValueError("Provided Search parameters are mutually exclusive.") assert sampling_topk < 0 or sampling, "--sampling-topk requires --sampling" assert sampling_topp < 0 or sampling, "--sampling-topp requires --sampling" if sampling: search_strategy = search.Sampling( self.target_dictionary, sampling_topk, sampling_topp ) elif diverse_beam_groups > 0: search_strategy = search.DiverseBeamSearch( self.target_dictionary, diverse_beam_groups, diverse_beam_strength ) elif match_source_len: # this is useful for tagging applications where the output # length should match the input length, so we hardcode the # length constraints for simplicity search_strategy = search.LengthConstrainedBeamSearch( self.target_dictionary, min_len_a=1, min_len_b=0, max_len_a=1, max_len_b=0, ) elif diversity_rate > -1: search_strategy = search.DiverseSiblingsSearch( self.target_dictionary, diversity_rate ) elif constrained: search_strategy = search.LexicallyConstrainedBeamSearch( self.target_dictionary, args.constraints ) elif prefix_allowed_tokens_fn: search_strategy = search.PrefixConstrainedBeamSearch( self.target_dictionary, prefix_allowed_tokens_fn ) else: search_strategy = search.BeamSearch(self.target_dictionary) if seq_gen_cls is None: if getattr(args, "print_alignment", False): seq_gen_cls = SequenceGeneratorWithAlignment else: seq_gen_cls = SequenceGenerator extra_gen_cls_kwargs = extra_gen_cls_kwargs or {} return seq_gen_cls( models, self.target_dictionary, beam_size=getattr(args, "beam", 5), max_len_a=getattr(args, "max_len_a", 0), max_len_b=getattr(args, "max_len_b", 200), min_len=getattr(args, "min_len", 1), normalize_scores=(not getattr(args, "unnormalized", False)), len_penalty=getattr(args, "lenpen", 1), unk_penalty=getattr(args, "unkpen", 0), temperature=getattr(args, "temperature", 1.0), match_source_len=getattr(args, "match_source_len", False), no_repeat_ngram_size=getattr(args, "no_repeat_ngram_size", 0), search_strategy=search_strategy, **extra_gen_cls_kwargs, )
[docs] def train_step( self, sample, model, criterion, optimizer, update_num, ignore_grad=False ): """ Do forward and backward, and return the loss as computed by *criterion* for the given *model* and *sample*. Args: sample (dict): the mini-batch. The format is defined by the :class:``. model (~fairseq.models.BaseFairseqModel): the model criterion (~fairseq.criterions.FairseqCriterion): the criterion optimizer (~fairseq.optim.FairseqOptimizer): the optimizer update_num (int): the current update ignore_grad (bool): multiply loss by 0 if this is set to True Returns: tuple: - the loss - the sample size, which is used as the denominator for the gradient - logging outputs to display while training """ model.train() model.set_num_updates(update_num) with torch.autograd.profiler.record_function("forward"): loss, sample_size, logging_output = criterion(model, sample) if ignore_grad: loss *= 0 with torch.autograd.profiler.record_function("backward"): optimizer.backward(loss) return loss, sample_size, logging_output
[docs] def valid_step(self, sample, model, criterion): model.eval() with torch.no_grad(): loss, sample_size, logging_output = criterion(model, sample) return loss, sample_size, logging_output
[docs] def inference_step( self, generator, models, sample, prefix_tokens=None, constraints=None ): with torch.no_grad(): return generator.generate( models, sample, prefix_tokens=prefix_tokens, constraints=constraints )
[docs] def begin_epoch(self, epoch, model): """Hook function called before the start of each epoch.""" pass
[docs] def begin_valid_epoch(self, epoch, model): """Hook function called before the start of each validation epoch.""" pass
[docs] def aggregate_logging_outputs(self, logging_outputs, criterion): """[deprecated] Aggregate logging outputs from data parallel training.""" utils.deprecation_warning( "The aggregate_logging_outputs API is deprecated. " "Please use the reduce_metrics API instead." ) with metrics.aggregate() as agg: self.reduce_metrics(logging_outputs, criterion) return agg.get_smoothed_values()
[docs] def reduce_metrics(self, logging_outputs, criterion): """Aggregate logging outputs from data parallel training.""" # backward compatibility for tasks that override aggregate_logging_outputs base_func = FairseqTask.aggregate_logging_outputs self_func = getattr(self, "aggregate_logging_outputs").__func__ if self_func is not base_func: utils.deprecation_warning( "Tasks should implement the reduce_metrics API. " "Falling back to deprecated aggregate_logging_outputs API." ) agg_logging_outputs = self.aggregate_logging_outputs( logging_outputs, criterion ) for k, v in agg_logging_outputs.items(): metrics.log_scalar(k, v) return if not any("ntokens" in log for log in logging_outputs): warnings.warn( "ntokens not found in Criterion logging outputs, cannot log wpb or wps" ) else: ntokens = sum(log.get("ntokens", 0) for log in logging_outputs) metrics.log_scalar("wpb", ntokens, priority=180, round=1) metrics.log_speed("wps", ntokens, priority=90, round=1) if not any("nsentences" in log for log in logging_outputs): warnings.warn( "nsentences not found in Criterion logging outputs, cannot log bsz" ) else: nsentences = sum(log.get("nsentences", 0) for log in logging_outputs) metrics.log_scalar("bsz", nsentences, priority=190, round=1) criterion.__class__.reduce_metrics(logging_outputs)
[docs] def max_positions(self): """Return the max input length allowed by the task.""" return None
@property def source_dictionary(self): """Return the source :class:`` (if applicable for this task).""" raise NotImplementedError @property def target_dictionary(self): """Return the target :class:`` (if applicable for this task).""" raise NotImplementedError
[docs] def build_tokenizer(self, args): """Build the pre-tokenizer for this task.""" return encoders.build_tokenizer(args)
[docs] def build_bpe(self, args): """Build the tokenizer for this task.""" return encoders.build_bpe(args)
class LegacyFairseqTask(FairseqTask): def __init__(self, args: Namespace): self.args = args self.datasets = {} self.dataset_to_epoch_iter = {} @classmethod def setup_task(cls, args: Namespace, **kwargs): """Setup the task (e.g., load dictionaries). Args: args (argparse.Namespace): parsed command-line arguments """ return cls(args, **kwargs) def has_sharded_data(self, split): return os.pathsep in getattr(self.args, "data", "") def build_model(self, args: Namespace): """ Build the :class:`~fairseq.models.BaseFairseqModel` instance for this task. Args: args (argparse.Namespace): parsed command-line arguments Returns: a :class:`~fairseq.models.BaseFairseqModel` instance """ from fairseq import models, quantization_utils model = models.build_model(args, self) if getattr(args, "tpu", False): model.prepare_for_tpu_() model = quantization_utils.quantize_model_scalar(model, args) return model def build_criterion(self, args: Namespace): """ Build the :class:`~fairseq.criterions.FairseqCriterion` instance for this task. Args: args (argparse.Namespace): parsed command-line arguments Returns: a :class:`~fairseq.criterions.FairseqCriterion` instance """ from fairseq import criterions return criterions.build_criterion(args, self)