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fix(training): lr scheduler doesn't work properly in distributed scenarios #8312

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merged 1 commit into from
May 30, 2024
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fix(training): lr scheduler doesn't work properly in distributed scenarios #8312

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25 changes: 18 additions & 7 deletions examples/text_to_image/train_text_to_image_lora.py
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Original file line number Diff line number Diff line change
Expand Up @@ -697,17 +697,22 @@ def collate_fn(examples):
)

# Scheduler and math around the number of training steps.
overrode_max_train_steps = False
num_update_steps_per_epoch = math.ceil(len(train_dataloader) / args.gradient_accumulation_steps)
# Check the PR https://github.com/huggingface/diffusers/pull/8312 for detailed explanation.
num_warmup_steps_for_scheduler = args.lr_warmup_steps * accelerator.num_processes
if args.max_train_steps is None:
args.max_train_steps = args.num_train_epochs * num_update_steps_per_epoch
overrode_max_train_steps = True
len_train_dataloader_after_sharding = math.ceil(len(train_dataloader) / accelerator.num_processes)
num_update_steps_per_epoch = math.ceil(len_train_dataloader_after_sharding / args.gradient_accumulation_steps)
num_training_steps_for_scheduler = (
args.num_train_epochs * num_update_steps_per_epoch * accelerator.num_processes
)
else:
num_training_steps_for_scheduler = args.max_train_steps * accelerator.num_processes

lr_scheduler = get_scheduler(
args.lr_scheduler,
optimizer=optimizer,
num_warmup_steps=args.lr_warmup_steps * accelerator.num_processes,
num_training_steps=args.max_train_steps * accelerator.num_processes,
num_warmup_steps=num_warmup_steps_for_scheduler,
num_training_steps=num_training_steps_for_scheduler,
)

# Prepare everything with our `accelerator`.
Expand All @@ -717,8 +722,14 @@ def collate_fn(examples):

# We need to recalculate our total training steps as the size of the training dataloader may have changed.
num_update_steps_per_epoch = math.ceil(len(train_dataloader) / args.gradient_accumulation_steps)
if overrode_max_train_steps:
if args.max_train_steps is None:
args.max_train_steps = args.num_train_epochs * num_update_steps_per_epoch
if num_training_steps_for_scheduler != args.max_train_steps * accelerator.num_processes:
logger.warning(
f"The length of the 'train_dataloader' after 'accelerator.prepare' ({len(train_dataloader)}) does not match "
f"the expected length ({len_train_dataloader_after_sharding}) when the learning rate scheduler was created. "
f"This inconsistency may result in the learning rate scheduler not functioning properly."
)
# Afterwards we recalculate our number of training epochs
args.num_train_epochs = math.ceil(args.max_train_steps / num_update_steps_per_epoch)

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