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# ------------------------------------------------------------------------------
# Reference: https://github.com/facebookresearch/detectron2/blob/main/detectron2/data/build.py
# Modified by Jitesh Jain (https://github.com/praeclarumjj3)
# ------------------------------------------------------------------------------
from typing import Any, Callable, Dict, List, Optional, Union
import torch.utils.data as torchdata
from detectron2.config import configurable
from detectron2.data.common import DatasetFromList, MapDataset
from detectron2.data.dataset_mapper import DatasetMapper
from detectron2.data.samplers import (
InferenceSampler,
)
from detectron2.data.build import (
get_detection_dataset_dicts,
trivial_batch_collator
)
"""
This file contains the default logic to build a dataloader for training or testing.
"""
__all__ = [
"build_detection_test_loader",
]
def _test_loader_from_config(cfg, dataset_name, mapper=None):
"""
Uses the given `dataset_name` argument (instead of the names in cfg), because the
standard practice is to evaluate each test set individually (not combining them).
"""
if isinstance(dataset_name, str):
dataset_name = [dataset_name]
dataset = get_detection_dataset_dicts(
dataset_name,
filter_empty=False,
proposal_files=[
cfg.DATASETS.PROPOSAL_FILES_TEST[list(cfg.DATASETS.TEST).index(x)] for x in dataset_name
]
if cfg.MODEL.LOAD_PROPOSALS
else None,
)
if mapper is None:
mapper = DatasetMapper(cfg, False)
return {
"dataset": dataset,
"mapper": mapper,
"num_workers": cfg.DATALOADER.NUM_WORKERS,
"sampler": InferenceSampler(len(dataset))
if not isinstance(dataset, torchdata.IterableDataset)
else None,
}
@configurable(from_config=_test_loader_from_config)
def build_detection_test_loader(
dataset: Union[List[Any], torchdata.Dataset],
*,
mapper: Callable[[Dict[str, Any]], Any],
sampler: Optional[torchdata.Sampler] = None,
batch_size: int = 1,
num_workers: int = 0,
collate_fn: Optional[Callable[[List[Any]], Any]] = None,
) -> torchdata.DataLoader:
"""
Similar to `build_detection_train_loader`, with default batch size = 1,
and sampler = :class:`InferenceSampler`. This sampler coordinates all workers
to produce the exact set of all samples.
Args:
dataset: a list of dataset dicts,
or a pytorch dataset (either map-style or iterable). They can be obtained
by using :func:`DatasetCatalog.get` or :func:`get_detection_dataset_dicts`.
mapper: a callable which takes a sample (dict) from dataset
and returns the format to be consumed by the model.
When using cfg, the default choice is ``DatasetMapper(cfg, is_train=False)``.
sampler: a sampler that produces
indices to be applied on ``dataset``. Default to :class:`InferenceSampler`,
which splits the dataset across all workers. Sampler must be None
if `dataset` is iterable.
batch_size: the batch size of the data loader to be created.
Default to 1 image per worker since this is the standard when reporting
inference time in papers.
num_workers: number of parallel data loading workers
collate_fn: same as the argument of `torch.utils.data.DataLoader`.
Defaults to do no collation and return a list of data.
Returns:
DataLoader: a torch DataLoader, that loads the given detection
dataset, with test-time transformation and batching.
Examples:
::
data_loader = build_detection_test_loader(
DatasetRegistry.get("my_test"),
mapper=DatasetMapper(...))
# or, instantiate with a CfgNode:
data_loader = build_detection_test_loader(cfg, "my_test")
"""
if isinstance(dataset, list):
dataset = DatasetFromList(dataset, copy=False)
if mapper is not None:
dataset = MapDataset(dataset, mapper)
if isinstance(dataset, torchdata.IterableDataset):
assert sampler is None, "sampler must be None if dataset is IterableDataset"
else:
if sampler is None:
sampler = InferenceSampler(len(dataset))
return torchdata.DataLoader(
dataset,
batch_size=batch_size,
sampler=sampler,
drop_last=False,
num_workers=num_workers,
collate_fn=trivial_batch_collator if collate_fn is None else collate_fn,
)