Refactor LoRA (huggingface#3778)

* refactor to support patching LoRA into T5

instantiate the lora linear layer on the same device as the regular linear layer

get lora rank from state dict

tests

fmt

can create lora layer in float32 even when rest of model is float16

fix loading model hook

remove load_lora_weights_ and T5 dispatching

remove Unet#attn_processors_state_dict

docstrings

* text encoder monkeypatch class method

* fix test

---------

Co-authored-by: Patrick von Platen <[email protected]>

Author: 2 people

examples/dreambooth/train_dreambooth_lora.py

@@ -23,6 +23,7 @@
 import shutil
 import warnings
 from pathlib import Path
+from typing import Dict
 
 import numpy as np
 import torch
@@ -50,7 +51,10 @@
     StableDiffusionPipeline,
     UNet2DConditionModel,
 )
-from diffusers.loaders import AttnProcsLayers, LoraLoaderMixin
+from diffusers.loaders import (
+    LoraLoaderMixin,
+    text_encoder_lora_state_dict,
+)
 from diffusers.models.attention_processor import (
     AttnAddedKVProcessor,
     AttnAddedKVProcessor2_0,
@@ -60,7 +64,7 @@
     SlicedAttnAddedKVProcessor,
 )
 from diffusers.optimization import get_scheduler
-from diffusers.utils import TEXT_ENCODER_ATTN_MODULE, check_min_version, is_wandb_available
+from diffusers.utils import check_min_version, is_wandb_available
 from diffusers.utils.import_utils import is_xformers_available
 
 
@@ -653,6 +657,22 @@ def encode_prompt(text_encoder, input_ids, attention_mask, text_encoder_use_atte
     return prompt_embeds
 
 
+def unet_attn_processors_state_dict(unet) -> Dict[str, torch.tensor]:
+    r"""
+    Returns:
+        a state dict containing just the attention processor parameters.
+    """
+    attn_processors = unet.attn_processors
+
+    attn_processors_state_dict = {}
+
+    for attn_processor_key, attn_processor in attn_processors.items():
+        for parameter_key, parameter in attn_processor.state_dict().items():
+            attn_processors_state_dict[f"{attn_processor_key}.{parameter_key}"] = parameter
+
+    return attn_processors_state_dict
+
+
 def main(args):
     logging_dir = Path(args.output_dir, args.logging_dir)
 
@@ -833,6 +853,7 @@ def main(args):
 
     # Set correct lora layers
     unet_lora_attn_procs = {}
+    unet_lora_parameters = []
     for name, attn_processor in unet.attn_processors.items():
         cross_attention_dim = None if name.endswith("attn1.processor") else unet.config.cross_attention_dim
         if name.startswith("mid_block"):
@@ -850,35 +871,18 @@ def main(args):
             lora_attn_processor_class = (
                 LoRAAttnProcessor2_0 if hasattr(F, "scaled_dot_product_attention") else LoRAAttnProcessor
             )
-        unet_lora_attn_procs[name] = lora_attn_processor_class(
-            hidden_size=hidden_size,
-            cross_attention_dim=cross_attention_dim,
-            rank=args.rank,
-        )
+            
+        module = lora_attn_processor_class(hidden_size=hidden_size, cross_attention_dim=cross_attention_dim)
+        unet_lora_attn_procs[name] = module
+        unet_lora_parameters.extend(module.parameters())
 
     unet.set_attn_processor(unet_lora_attn_procs)
-    unet_lora_layers = AttnProcsLayers(unet.attn_processors)
 
     # The text encoder comes from 🤗 transformers, so we cannot directly modify it.
-    # So, instead, we monkey-patch the forward calls of its attention-blocks. For this,
-    # we first load a dummy pipeline with the text encoder and then do the monkey-patching.
-    text_encoder_lora_layers = None
+    # So, instead, we monkey-patch the forward calls of its attention-blocks.
     if args.train_text_encoder:
-        text_lora_attn_procs = {}
-        for name, module in text_encoder.named_modules():
-            if name.endswith(TEXT_ENCODER_ATTN_MODULE):
-                text_lora_attn_procs[name] = LoRAAttnProcessor(
-                    hidden_size=module.out_proj.out_features,
-                    cross_attention_dim=None,
-                    rank=args.rank,
-                )
-        text_encoder_lora_layers = AttnProcsLayers(text_lora_attn_procs)
-        temp_pipeline = DiffusionPipeline.from_pretrained(
-            args.pretrained_model_name_or_path, text_encoder=text_encoder
-        )
-        temp_pipeline._modify_text_encoder(text_lora_attn_procs)
-        text_encoder = temp_pipeline.text_encoder
-        del temp_pipeline
+        # ensure that dtype is float32, even if rest of the model that isn't trained is loaded in fp16
+        text_lora_parameters = LoraLoaderMixin._modify_text_encoder(text_encoder, dtype=torch.float32)
 
     # create custom saving & loading hooks so that `accelerator.save_state(...)` serializes in a nice format
     def save_model_hook(models, weights, output_dir):
@@ -887,23 +891,13 @@ def save_model_hook(models, weights, output_dir):
         unet_lora_layers_to_save = None
         text_encoder_lora_layers_to_save = None
 
-        if args.train_text_encoder:
-            text_encoder_keys = accelerator.unwrap_model(text_encoder_lora_layers).state_dict().keys()
-        unet_keys = accelerator.unwrap_model(unet_lora_layers).state_dict().keys()
-
         for model in models:
-            state_dict = model.state_dict()
-
-            if (
-                text_encoder_lora_layers is not None
-                and text_encoder_keys is not None
-                and state_dict.keys() == text_encoder_keys
-            ):
-                # text encoder
-                text_encoder_lora_layers_to_save = state_dict
-            elif state_dict.keys() == unet_keys:
-                # unet
-                unet_lora_layers_to_save = state_dict
+            if isinstance(model, type(accelerator.unwrap_model(unet))):
+                unet_lora_layers_to_save = unet_attn_processors_state_dict(model)
+            elif isinstance(model, type(accelerator.unwrap_model(text_encoder))):
+                text_encoder_lora_layers_to_save = text_encoder_lora_state_dict(model)
+            else:
+                raise ValueError(f"unexpected save model: {model.__class__}")
 
             # make sure to pop weight so that corresponding model is not saved again
             weights.pop()
@@ -915,27 +909,24 @@ def save_model_hook(models, weights, output_dir):
         )
 
     def load_model_hook(models, input_dir):
-        # Note we DON'T pass the unet and text encoder here an purpose
-        # so that the we don't accidentally override the LoRA layers of
-        # unet_lora_layers and text_encoder_lora_layers which are stored in `models`
-        # with new torch.nn.Modules / weights. We simply use the pipeline class as
-        # an easy way to load the lora checkpoints
-        temp_pipeline = DiffusionPipeline.from_pretrained(
-            args.pretrained_model_name_or_path,
-            revision=args.revision,
-            torch_dtype=weight_dtype,
-        )
-        temp_pipeline.load_lora_weights(input_dir)
+        unet_ = None
+        text_encoder_ = None
 
-        # load lora weights into models
-        models[0].load_state_dict(AttnProcsLayers(temp_pipeline.unet.attn_processors).state_dict())
-        if len(models) > 1:
-            models[1].load_state_dict(AttnProcsLayers(temp_pipeline.text_encoder_lora_attn_procs).state_dict())
+        while len(models) > 0:
+            model = models.pop()
 
-        # delete temporary pipeline and pop models
-        del temp_pipeline
-        for _ in range(len(models)):
-            models.pop()
+            if isinstance(model, type(accelerator.unwrap_model(unet))):
+                unet_ = model
+            elif isinstance(model, type(accelerator.unwrap_model(text_encoder))):
+                text_encoder_ = model
+            else:
+                raise ValueError(f"unexpected save model: {model.__class__}")
+
+        lora_state_dict, network_alpha = LoraLoaderMixin.lora_state_dict(input_dir)
+        LoraLoaderMixin.load_lora_into_unet(lora_state_dict, network_alpha=network_alpha, unet=unet_)
+        LoraLoaderMixin.load_lora_into_text_encoder(
+            lora_state_dict, network_alpha=network_alpha, text_encoder=text_encoder_
+        )
 
     accelerator.register_save_state_pre_hook(save_model_hook)
     accelerator.register_load_state_pre_hook(load_model_hook)
@@ -965,9 +956,9 @@ def load_model_hook(models, input_dir):
 
     # Optimizer creation
     params_to_optimize = (
-        itertools.chain(unet_lora_layers.parameters(), text_encoder_lora_layers.parameters())
+        itertools.chain(unet_lora_parameters, text_lora_parameters)
         if args.train_text_encoder
-        else unet_lora_layers.parameters()
+        else unet_lora_parameters
     )
     optimizer = optimizer_class(
         params_to_optimize,
@@ -1056,12 +1047,12 @@ def compute_text_embeddings(prompt):
 
     # Prepare everything with our `accelerator`.
     if args.train_text_encoder:
-        unet_lora_layers, text_encoder_lora_layers, optimizer, train_dataloader, lr_scheduler = accelerator.prepare(
-            unet_lora_layers, text_encoder_lora_layers, optimizer, train_dataloader, lr_scheduler
+        unet, text_encoder, optimizer, train_dataloader, lr_scheduler = accelerator.prepare(
+            unet, text_encoder, optimizer, train_dataloader, lr_scheduler
         )
     else:
-        unet_lora_layers, optimizer, train_dataloader, lr_scheduler = accelerator.prepare(
-            unet_lora_layers, optimizer, train_dataloader, lr_scheduler
+        unet, optimizer, train_dataloader, lr_scheduler = accelerator.prepare(
+            unet, optimizer, train_dataloader, lr_scheduler
         )
 
     # We need to recalculate our total training steps as the size of the training dataloader may have changed.
@@ -1210,9 +1201,9 @@ def compute_text_embeddings(prompt):
                 accelerator.backward(loss)
                 if accelerator.sync_gradients:
                     params_to_clip = (
-                        itertools.chain(unet_lora_layers.parameters(), text_encoder_lora_layers.parameters())
+                        itertools.chain(unet_lora_parameters, text_lora_parameters)
                         if args.train_text_encoder
-                        else unet_lora_layers.parameters()
+                        else unet_lora_parameters
                     )
                     accelerator.clip_grad_norm_(params_to_clip, args.max_grad_norm)
                 optimizer.step()
@@ -1301,15 +1292,17 @@ def compute_text_embeddings(prompt):
                     pipeline_args = {"prompt": args.validation_prompt}
 
                 if args.validation_images is None:
-                    images = [
-                        pipeline(**pipeline_args, generator=generator).images[0]
-                        for _ in range(args.num_validation_images)
-                    ]
+                    images = []
+                    for _ in range(args.num_validation_images):
+                        with torch.cuda.amp.autocast():
+                            image = pipeline(**pipeline_args, generator=generator).images[0]
+                            images.append(image)
                 else:
                     images = []
                     for image in args.validation_images:
                         image = Image.open(image)
-                        image = pipeline(**pipeline_args, image=image, generator=generator).images[0]
+                        with torch.cuda.amp.autocast():
+                            image = pipeline(**pipeline_args, image=image, generator=generator).images[0]
                         images.append(image)
 
                 for tracker in accelerator.trackers:
@@ -1332,12 +1325,16 @@ def compute_text_embeddings(prompt):
     # Save the lora layers
     accelerator.wait_for_everyone()
     if accelerator.is_main_process:
+        unet = accelerator.unwrap_model(unet)
         unet = unet.to(torch.float32)
-        unet_lora_layers = accelerator.unwrap_model(unet_lora_layers)
+        unet_lora_layers = unet_attn_processors_state_dict(unet)
 
-        if text_encoder is not None:
+        if text_encoder is not None and args.train_text_encoder:
+            text_encoder = accelerator.unwrap_model(text_encoder)
             text_encoder = text_encoder.to(torch.float32)
-            text_encoder_lora_layers = accelerator.unwrap_model(text_encoder_lora_layers)
+            text_encoder_lora_layers = text_encoder_lora_state_dict(text_encoder)
+        else:
+            text_encoder_lora_layers = None
 
         LoraLoaderMixin.save_lora_weights(
             save_directory=args.output_dir,