From f2051af4432f57d13626cea8e2d76809d5b6b438 Mon Sep 17 00:00:00 2001 From: Zhiqi Zhang Date: Thu, 20 Aug 2026 04:19:42 +0000 Subject: [PATCH] [train_text_to_image_decoder.py] Fix the LR scheduler when num_train_epochs is passed in a distributed training env --- .../train_text_to_image_decoder.py | 25 +++++++++++++------ 1 file changed, 18 insertions(+), 7 deletions(-) diff --git a/examples/kandinsky2_2/text_to_image/train_text_to_image_decoder.py b/examples/kandinsky2_2/text_to_image/train_text_to_image_decoder.py index 69934c0625f3..1b2354fc7fe3 100644 --- a/examples/kandinsky2_2/text_to_image/train_text_to_image_decoder.py +++ b/examples/kandinsky2_2/text_to_image/train_text_to_image_decoder.py @@ -684,17 +684,22 @@ 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 * accelerator.num_processes * num_update_steps_per_epoch + ) + 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 * args.gradient_accumulation_steps, - num_training_steps=args.max_train_steps * args.gradient_accumulation_steps, + num_warmup_steps=num_warmup_steps_for_scheduler, + num_training_steps=num_training_steps_for_scheduler, ) unet, optimizer, train_dataloader, lr_scheduler = accelerator.prepare( unet, optimizer, train_dataloader, lr_scheduler @@ -704,8 +709,14 @@ def collate_fn(examples): vae.to(accelerator.device, dtype=weight_dtype) # 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)