def load(self, checkpoint_path: str):
r"""
Load a serialized checkpoint from a path. This method will try to find
each of :attr:`checkpointables` in the file and load its state dict.
Since our checkpointables are held as references, this method does not
return them.
Parameters
----------
checkpoint_path: str
Path to a checkpoint serialized by :meth:`step`.
Returns
-------
int
Iteration corresponding to the loaded checkpoint. Useful for
resuming training. This will be -1 in case of best checkpoint,
or if info does not exist.
"""
# Each process will log a message after loading checkpoint.
rank = dist.get_rank()
logger.info(f"Rank {rank}: Loading checkpoint from {checkpoint_path}")
checkpoint = torch.load(checkpoint_path, map_location="cpu")
iteration = checkpoint.pop("iteration", -1)
# Keep flags of all checkpointables to lo which ones were not loaded.
is_loaded = {key: False for key in self.checkpointables}
# Load each checkpointable from checkpoint.
for key in checkpoint:
if key in self.checkpointables:
logger.info(
f"Rank {rank}: Loading {key} from {checkpoint_path}")
if isinstance(self.checkpointables[key],
nn.parallel.DistributedDataParallel):
self.checkpointables[key].module.load_state_dict(
checkpoint[key])
else:
self.checkpointables[key].load_state_dict(checkpoint[key])
is_loaded[key] = True
else:
logger.info(
f"Rank {rank}: {key} not found in `checkpointables`.")
not_loaded: List[str] = [
key for key in is_loaded if not is_loaded[key]
]
if len(not_loaded) > 0:
logger.info(
f"Rank {rank}: Checkpointables not found in file: {not_loaded}"
)
return iteration
def __init__(self, cfg, weights: Union[str, Dict[str, Any]]):
self.start_iter = 0
self.max_iter = cfg.SOLVER.MAX_ITER
self.cfg = cfg
# We do not make any super call here and implement `__init__` from
# `DefaultTrainer`: we need to initialize mixed precision model before
# wrapping to DDP, so we need to do it this way.
model = self.build_model(cfg)
optimizer = self.build_optimizer(cfg, model)
data_loader = self.build_train_loader(cfg)
scheduler = self.build_lr_scheduler(cfg, optimizer)
# Load pre-trained weights before wrapping to DDP because `ApexDDP` has
# some weird issue with `DetectionCheckpointer`.
# fmt: off
if isinstance(weights, str):
# weights are ``str`` means ImageNet init or resume training.
self.start_iter = (DetectionCheckpointer(
model, optimizer=optimizer,
scheduler=scheduler).resume_or_load(weights, resume=True).get(
"iteration", -1) + 1)
elif isinstance(weights, dict):
# weights are a state dict means our pretrain init.
DetectionCheckpointer(model)._load_model(weights)
# fmt: on
# Enable distributed training if we have multiple GPUs. Use Apex DDP for
# non-FPN backbones because its `delay_allreduce` functionality helps with
# gradient checkpointing.
if dist.get_world_size() > 1:
if global_cfg.get("GRADIENT_CHECKPOINT", False):
model = ApexDDP(model, delay_allreduce=True)
else:
model = nn.parallel.DistributedDataParallel(
model,
device_ids=[dist.get_rank()],
broadcast_buffers=False)
# Call `__init__` from grandparent class: `SimpleTrainer`.
SimpleTrainer.__init__(self, model, data_loader, optimizer)
self.scheduler = scheduler
self.checkpointer = DetectionCheckpointer(model,
cfg.OUTPUT_DIR,
optimizer=optimizer,
scheduler=self.scheduler)
self.register_hooks(self.build_hooks())
def common_setup(_C: Config,
_A: argparse.Namespace,
job_type: str = "pretrain"):
r"""
Setup common stuff at the start of every pretraining or downstream
evaluation job, all listed here to avoid code duplication. Basic steps:
1. Fix random seeds and other PyTorch flags.
2. Set up a serialization directory and loggers.
3. Log important stuff such as config, process info (useful during
distributed training).
4. Save a copy of config to serialization directory.
.. note::
It is assumed that multiple processes for distributed training have
already been launched from outside. Functions from
:mod:`virtex.utils.distributed` module ae used to get process info.
Args:
_C: Config object with all the parameters.
_A: Argparse command line arguments.
job_type: Type of job for which setup is to be done; one of
``{"pretrain", "downstream"}``.
"""
# Get process rank and world size (assuming distributed is initialized).
RANK = dist.get_rank()
WORLD_SIZE = dist.get_world_size()
# For reproducibility - refer https://pytorch.org/docs/stable/notes/randomness.html
torch.manual_seed(_C.RANDOM_SEED)
torch.backends.cudnn.deterministic = _C.CUDNN_DETERMINISTIC
torch.backends.cudnn.benchmark = _C.CUDNN_BENCHMARK
random.seed(_C.RANDOM_SEED)
np.random.seed(_C.RANDOM_SEED)
# Create serialization directory and save config in it.
os.makedirs(_A.serialization_dir, exist_ok=True)
_C.dump(os.path.join(_A.serialization_dir, f"{job_type}_config.yaml"))
# Remove default logger, create a logger for each process which writes to a
# separate log-file. This makes changes in global scope.
logger.remove(0)
if dist.get_world_size() > 1:
logger.add(
os.path.join(_A.serialization_dir, f"log-rank{RANK}.txt"),
format="{time} {level} {message}",
)
# Add a logger for stdout only for the master process.
if dist.is_master_process():
logger.add(sys.stdout,
format="<g>{time}</g>: <lvl>{message}</lvl>",
colorize=True)
# Print process info, config and args.
logger.info(f"Rank of current process: {RANK}. World size: {WORLD_SIZE}")
logger.info(str(_C))
logger.info("Command line args:")
for arg in vars(_A):
logger.info("{:<20}: {}".format(arg, getattr(_A, arg)))
def main(_A: argparse.Namespace):
if _A.num_gpus_per_machine == 0:
# Set device as CPU if num_gpus_per_machine = 0.
device = torch.device("cpu")
else:
# Get the current device as set for current distributed process.
# Check `launch` function in `virtex.utils.distributed` module.
device = torch.cuda.current_device()
# Create a downstream config object (this will be immutable) and perform
# common setup such as logging and setting up serialization directory.
_DOWNC = Config(_A.down_config, _A.down_config_override)
common_setup(_DOWNC, _A, job_type="downstream")
# Create a (pretraining) config object and backup in serializaion directory.
_C = Config(_A.config, _A.config_override)
_C.dump(os.path.join(_A.serialization_dir, "pretrain_config.yaml"))
# Get dataset name for tensorboard logging.
DATASET = _DOWNC.DATA.ROOT.split("/")[-1]
# Set number of output classes according to dataset:
NUM_CLASSES_MAPPING = {"imagenet": 1000, "inaturalist": 8142}
NUM_CLASSES = NUM_CLASSES_MAPPING[DATASET]
# -------------------------------------------------------------------------
# INSTANTIATE DATALOADER, MODEL, OPTIMIZER, SCHEDULER
# -------------------------------------------------------------------------
train_dataset = DownstreamDatasetFactory.from_config(_DOWNC, split="train")
train_dataloader = DataLoader(
train_dataset,
batch_size=_DOWNC.OPTIM.BATCH_SIZE // dist.get_world_size(),
num_workers=_A.cpu_workers,
sampler=DistributedSampler(
train_dataset,
num_replicas=dist.get_world_size(),
rank=dist.get_rank(),
shuffle=True,
),
drop_last=False,
pin_memory=True,
collate_fn=train_dataset.collate_fn,
)
val_dataset = DownstreamDatasetFactory.from_config(_DOWNC, split="val")
val_dataloader = DataLoader(
val_dataset,
batch_size=_DOWNC.OPTIM.BATCH_SIZE // dist.get_world_size(),
num_workers=_A.cpu_workers,
sampler=DistributedSampler(
val_dataset,
num_replicas=dist.get_world_size(),
rank=dist.get_rank(),
shuffle=False,
),
pin_memory=True,
drop_last=False,
collate_fn=val_dataset.collate_fn,
)
# Initialize model using pretraining config.
pretrained_model = PretrainingModelFactory.from_config(_C)
# Load weights according to the init method, do nothing for `random`, and
# `imagenet` is already taken care of.
if _A.weight_init == "virtex":
CheckpointManager(model=pretrained_model).load(_A.checkpoint_path)
elif _A.weight_init == "torchvision":
# Keep strict=False because this state dict may have weights for
# last fc layer.
pretrained_model.visual.cnn.load_state_dict(
torch.load(_A.checkpoint_path, map_location="cpu")["state_dict"],
strict=False,
)
# Pull out the CNN (torchvision-like) from our pretrained model and add
# back the FC layer - this is exists in torchvision models, and is set to
# `nn.Identity()` during pretraining.
model = pretrained_model.visual.cnn # type: ignore
model.fc = nn.Linear(_DOWNC.MODEL.VISUAL.FEATURE_SIZE,
NUM_CLASSES).to(device)
model = model.to(device)
# Re-initialize the FC layer.
torch.nn.init.normal_(model.fc.weight.data, mean=0.0, std=0.01)
torch.nn.init.constant_(model.fc.bias.data, 0.0)
# Freeze all layers except FC as per config param.
if _DOWNC.MODEL.VISUAL.FROZEN:
for name, param in model.named_parameters():
if "fc" not in name:
param.requires_grad = False
# Cross entropy loss and accuracy meter.
criterion = nn.CrossEntropyLoss()
top1 = TopkAccuracy(top_k=1)
optimizer = OptimizerFactory.from_config(_DOWNC, model.named_parameters())
scheduler = LRSchedulerFactory.from_config(_DOWNC, optimizer)
del pretrained_model
# -------------------------------------------------------------------------
# BEFORE TRAINING STARTS
# -------------------------------------------------------------------------
# Create an iterator from dataloader to sample batches perpetually.
train_dataloader_iter = cycle(train_dataloader, device)
# Wrap model and optimizer using NVIDIA Apex for mixed precision training.
# NOTE: Always do this before wrapping model with DistributedDataParallel.
if _DOWNC.FP16_OPT > 0:
from apex import amp
model, optimizer = amp.initialize(model,
optimizer,
opt_level=f"O{_DOWNC.FP16_OPT}")
if dist.get_world_size() > 1:
dist.synchronize()
model = nn.parallel.DistributedDataParallel(
model, device_ids=[device], find_unused_parameters=True)
if dist.is_master_process():
checkpoint_manager = CheckpointManager(
_A.serialization_dir,
model=model,
optimizer=optimizer,
scheduler=scheduler,
)
tensorboard_writer = SummaryWriter(log_dir=_A.serialization_dir)
# Keep track of time per iteration and ETA.
timer = Timer(start_from=1, total_iterations=_DOWNC.OPTIM.NUM_ITERATIONS)
# -------------------------------------------------------------------------
# TRAINING LOOP
# -------------------------------------------------------------------------
for iteration in range(1, _DOWNC.OPTIM.NUM_ITERATIONS + 1):
timer.tic()
optimizer.zero_grad()
batch = next(train_dataloader_iter)
logits = model(batch["image"])
loss = criterion(logits, batch["label"])
# Perform dynamic scaling of loss to adjust for mixed precision.
if _DOWNC.FP16_OPT > 0:
with amp.scale_loss(loss, optimizer) as scaled_loss:
scaled_loss.backward()
else:
loss.backward()
optimizer.step()
scheduler.step(iteration)
timer.toc()
if iteration % _A.log_every == 0 and dist.is_master_process():
logger.info(
f"{timer.stats} | Loss: {loss:.3f} | GPU: {dist.gpu_mem_usage()} MB"
)
tensorboard_writer.add_scalar(f"{DATASET}/train_loss", loss,
iteration)
tensorboard_writer.add_scalar(
f"{DATASET}/learning_rate",
optimizer.param_groups[0]["lr"],
iteration,
)
# ---------------------------------------------------------------------
# VALIDATION
# ---------------------------------------------------------------------
if iteration % _A.checkpoint_every == 0:
torch.set_grad_enabled(False)
model.eval()
total_val_loss = torch.tensor(0.0).to(device)
for val_iteration, batch in enumerate(val_dataloader, start=1):
for key in batch:
batch[key] = batch[key].to(device)
logits = model(batch["image"])
loss = criterion(logits, batch["label"])
top1(logits, batch["label"])
total_val_loss += loss
# Divide each loss component by number of val batches per GPU.
total_val_loss = total_val_loss / val_iteration
dist.average_across_processes(total_val_loss)
# Get accumulated Top-1 accuracy for logging across GPUs.
acc = top1.get_metric(reset=True)
dist.average_across_processes(acc)
torch.set_grad_enabled(True)
model.train()
# Save recent checkpoint and best checkpoint based on accuracy.
if dist.is_master_process():
checkpoint_manager.step(iteration)
if iteration % _A.checkpoint_every == 0 and dist.is_master_process():
logger.info(f"Iter: {iteration} | Top-1 accuracy: {acc})")
tensorboard_writer.add_scalar(f"{DATASET}/val_loss",
total_val_loss, iteration)
# This name scoping will result in Tensorboard displaying all metrics
# (VOC07, caption, etc.) together.
tensorboard_writer.add_scalars(f"metrics/{DATASET}", {"top1": acc},
iteration)
# All processes will wait till master process is done logging.
dist.synchronize()