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# Copyright (c) Facebook, Inc. and its affiliates.
import logging
import os
import pickle
import torch
from fvcore.common.checkpoint import Checkpointer
from torch.nn.parallel import DistributedDataParallel
import detectron2.utils.comm as comm
from detectron2.utils.file_io import PathManager
from .c2_model_loading import align_and_update_state_dicts
class DetectionCheckpointer(Checkpointer):
"""
Same as :class:`Checkpointer`, but is able to:
1. handle models in detectron & detectron2 model zoo, and apply conversions for legacy models.
2. correctly load checkpoints that are only available on the master worker
"""
def __init__(self, model, save_dir="", *, save_to_disk=None, **checkpointables):
is_main_process = comm.is_main_process()
super().__init__(
model,
save_dir,
save_to_disk=is_main_process if save_to_disk is None else save_to_disk,
**checkpointables,
)
self.path_manager = PathManager
def load(self, path, *args, **kwargs):
need_sync = False
if path and isinstance(self.model, DistributedDataParallel):
logger = logging.getLogger(__name__)
path = self.path_manager.get_local_path(path)
has_file = os.path.isfile(path)
all_has_file = comm.all_gather(has_file)
if not all_has_file[0]:
raise OSError(f"File {path} not found on main worker.")
if not all(all_has_file):
logger.warning(
f"Not all workers can read checkpoint {path}. "
"Training may fail to fully resume."
)
# TODO: broadcast the checkpoint file contents from main
# worker, and load from it instead.
need_sync = True
if not has_file:
path = None # don't load if not readable
ret = super().load(path, *args, **kwargs)
if need_sync:
logger.info("Broadcasting model states from main worker ...")
self.model._sync_params_and_buffers()
return ret
def _load_file(self, filename):
if filename.endswith(".pkl"):
with PathManager.open(filename, "rb") as f:
data = pickle.load(f, encoding="latin1")
if "model" in data and "__author__" in data:
# file is in Detectron2 model zoo format
self.logger.info("Reading a file from '{}'".format(data["__author__"]))
return data
else:
# assume file is from Caffe2 / Detectron1 model zoo
if "blobs" in data:
# Detection models have "blobs", but ImageNet models don't
data = data["blobs"]
data = {k: v for k, v in data.items() if not k.endswith("_momentum")}
return {"model": data, "__author__": "Caffe2", "matching_heuristics": True}
elif filename.endswith(".pyth"):
# assume file is from pycls; no one else seems to use the ".pyth" extension
with PathManager.open(filename, "rb") as f:
data = torch.load(f)
assert (
"model_state" in data
), f"Cannot load .pyth file {filename}; pycls checkpoints must contain 'model_state'."
model_state = {
k: v
for k, v in data["model_state"].items()
if not k.endswith("num_batches_tracked")
}
return {"model": model_state, "__author__": "pycls", "matching_heuristics": True}
loaded = super()._load_file(filename) # load native pth checkpoint
if "model" not in loaded:
loaded = {"model": loaded}
return loaded
def _load_model(self, checkpoint):
if checkpoint.get("matching_heuristics", False):
self._convert_ndarray_to_tensor(checkpoint["model"])
# convert weights by name-matching heuristics
checkpoint["model"] = align_and_update_state_dicts(
self.model.state_dict(),
checkpoint["model"],
c2_conversion=checkpoint.get("__author__", None) == "Caffe2",
)
# for non-caffe2 models, use standard ways to load it
incompatible = super()._load_model(checkpoint)
model_buffers = dict(self.model.named_buffers(recurse=False))
for k in ["pixel_mean", "pixel_std"]:
# Ignore missing key message about pixel_mean/std.
# Though they may be missing in old checkpoints, they will be correctly
# initialized from config anyway.
if k in model_buffers:
try:
incompatible.missing_keys.remove(k)
except ValueError:
pass
for k in incompatible.unexpected_keys[:]:
# Ignore unexpected keys about cell anchors. They exist in old checkpoints
# but now they are non-persistent buffers and will not be in new checkpoints.
if "anchor_generator.cell_anchors" in k:
incompatible.unexpected_keys.remove(k)
return incompatible
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