[Feat] add: utility for unloading lora. (#4034)

* add: test for testing unloading lora.

* add :reason to skipif.

* initial implementation of lora unload().

* apply styling.

* add: doc.

* change checkpoints.

* reinit generator

* finalize slow test.

* add fast test for unloading lora.

docs/source/en/training/lora.mdx

@@ -280,6 +280,10 @@ Note that the use of [`~diffusers.loaders.LoraLoaderMixin.load_lora_weights`] is
 **Note** that it is possible to provide a local directory path to [`~diffusers.loaders.LoraLoaderMixin.load_lora_weights`] as well as [`~diffusers.loaders.UNet2DConditionLoadersMixin.load_attn_procs`]. To know about the supported inputs,
 refer to the respective docstrings.
 
+## Unloading LoRA parameters
+
+You can call [`~diffusers.loaders.LoraLoaderMixin.unload_lora_weights`] on a pipeline to unload the LoRA parameters.
+
 ## Supporting A1111 themed LoRA checkpoints from Diffusers
 
 To provide seamless interoperability with A1111 to our users, we support loading A1111 formatted

src/diffusers/loaders.py

@@ -25,6 +25,8 @@ from torch import nn
 from .models.attention_processor import (
     AttnAddedKVProcessor,
     AttnAddedKVProcessor2_0,
+    AttnProcessor,
+    AttnProcessor2_0,
     CustomDiffusionAttnProcessor,
     CustomDiffusionXFormersAttnProcessor,
     LoRAAttnAddedKVProcessor,
@@ -1270,6 +1272,38 @@ class LoraLoaderMixin:
         new_state_dict = {**unet_state_dict, **te_state_dict}
         return new_state_dict, network_alpha
 
+    def unload_lora_weights(self):
+        """
+        Unloads the LoRA parameters.
+
+        Examples:
+
+        ```python
+        >>> # Assuming `pipeline` is already loaded with the LoRA parameters.
+        >>> pipeline.unload_lora_weights()
+        >>> ...
+        ```
+        """
+        is_unet_lora = all(
+            isinstance(processor, (LoRAAttnProcessor2_0, LoRAAttnProcessor, LoRAAttnAddedKVProcessor))
+            for _, processor in self.unet.attn_processors.items()
+        )
+        # Handle attention processors that are a mix of regular attention and AddedKV
+        # attention.
+        if is_unet_lora:
+            is_attn_procs_mixed = all(
+                isinstance(processor, (LoRAAttnProcessor2_0, LoRAAttnProcessor))
+                for _, processor in self.unet.attn_processors.items()
+            )
+            if not is_attn_procs_mixed:
+                unet_attn_proc_cls = AttnProcessor2_0 if hasattr(F, "scaled_dot_product_attention") else AttnProcessor
+                self.unet.set_attn_processor(unet_attn_proc_cls())
+            else:
+                self.unet.set_default_attn_processor()
+
+        # Safe to call the following regardless of LoRA.
+        self._remove_text_encoder_monkey_patch()
+
 
 class FromSingleFileMixin:
     """

tests/models/test_lora_layers.py

@@ -83,9 +83,9 @@ def create_text_encoder_lora_layers(text_encoder: nn.Module):
     return text_encoder_lora_layers
 
 
-def set_lora_weights(text_lora_attn_parameters, randn_weight=False):
+def set_lora_weights(lora_attn_parameters, randn_weight=False):
     with torch.no_grad():
-        for parameter in text_lora_attn_parameters:
+        for parameter in lora_attn_parameters:
             if randn_weight:
                 parameter[:] = torch.randn_like(parameter)
             else:
@@ -155,7 +155,7 @@ class LoraLoaderMixinTests(unittest.TestCase):
         }
         return pipeline_components, lora_components
 
-    def get_dummy_inputs(self):
+    def get_dummy_inputs(self, with_generator=True):
         batch_size = 1
         sequence_length = 10
         num_channels = 4
@@ -167,16 +167,16 @@ class LoraLoaderMixinTests(unittest.TestCase):
 
         pipeline_inputs = {
             "prompt": "A painting of a squirrel eating a burger",
-            "generator": generator,
             "num_inference_steps": 2,
             "guidance_scale": 6.0,
-            "output_type": "numpy",
+            "output_type": "np",
         }
+        if with_generator:
+            pipeline_inputs.update({"generator": generator})
 
         return noise, input_ids, pipeline_inputs
 
-        # copied from: https://colab.research.google.com/gist/sayakpaul/df2ef6e1ae6d8c10a49d859883b10860/scratchpad.ipynb
-
+    # copied from: https://colab.research.google.com/gist/sayakpaul/df2ef6e1ae6d8c10a49d859883b10860/scratchpad.ipynb
     def get_dummy_tokens(self):
         max_seq_length = 77
 
@@ -399,6 +399,45 @@ class LoraLoaderMixinTests(unittest.TestCase):
                     )
                     self.assertIsInstance(module.processor, attn_proc_class)
 
+    def test_unload_lora(self):
+        pipeline_components, lora_components = self.get_dummy_components()
+        _, _, pipeline_inputs = self.get_dummy_inputs(with_generator=False)
+        sd_pipe = StableDiffusionPipeline(**pipeline_components)
+
+        original_images = sd_pipe(**pipeline_inputs, generator=torch.manual_seed(0)).images
+        orig_image_slice = original_images[0, -3:, -3:, -1]
+
+        # Emulate training.
+        set_lora_weights(lora_components["unet_lora_layers"].parameters(), randn_weight=True)
+        set_lora_weights(lora_components["text_encoder_lora_layers"].parameters(), randn_weight=True)
+
+        with tempfile.TemporaryDirectory() as tmpdirname:
+            LoraLoaderMixin.save_lora_weights(
+                save_directory=tmpdirname,
+                unet_lora_layers=lora_components["unet_lora_layers"],
+                text_encoder_lora_layers=lora_components["text_encoder_lora_layers"],
+            )
+            self.assertTrue(os.path.isfile(os.path.join(tmpdirname, "pytorch_lora_weights.bin")))
+            sd_pipe.load_lora_weights(tmpdirname)
+
+        lora_images = sd_pipe(**pipeline_inputs, generator=torch.manual_seed(0)).images
+        lora_image_slice = lora_images[0, -3:, -3:, -1]
+
+        # Unload LoRA parameters.
+        sd_pipe.unload_lora_weights()
+        original_images_two = sd_pipe(**pipeline_inputs, generator=torch.manual_seed(0)).images
+        orig_image_slice_two = original_images_two[0, -3:, -3:, -1]
+
+        assert not np.allclose(
+            orig_image_slice, lora_image_slice
+        ), "LoRA parameters should lead to a different image slice."
+        assert not np.allclose(
+            orig_image_slice_two, lora_image_slice
+        ), "LoRA parameters should lead to a different image slice."
+        assert np.allclose(
+            orig_image_slice, orig_image_slice_two, atol=1e-3
+        ), "Unloading LoRA parameters should lead to results similar to what was obtained with the pipeline without any LoRA parameters."
+
     @unittest.skipIf(torch_device != "cuda", "This test is supposed to run on GPU")
     def test_lora_unet_attn_processors_with_xformers(self):
         with tempfile.TemporaryDirectory() as tmpdirname:
@@ -537,3 +576,35 @@ class LoraIntegrationTests(unittest.TestCase):
         expected = np.array([0.7406, 0.699, 0.5963, 0.7493, 0.7045, 0.6096, 0.6886, 0.6388, 0.583])
 
         self.assertTrue(np.allclose(images, expected, atol=1e-4))
+
+    def test_unload_lora(self):
+        generator = torch.manual_seed(0)
+        prompt = "masterpiece, best quality, mountain"
+        num_inference_steps = 2
+
+        pipe = StableDiffusionPipeline.from_pretrained("runwayml/stable-diffusion-v1-5", safety_checker=None).to(
+            torch_device
+        )
+        initial_images = pipe(
+            prompt, output_type="np", generator=generator, num_inference_steps=num_inference_steps
+        ).images
+        initial_images = initial_images[0, -3:, -3:, -1].flatten()
+
+        lora_model_id = "hf-internal-testing/civitai-colored-icons-lora"
+        lora_filename = "Colored_Icons_by_vizsumit.safetensors"
+
+        pipe.load_lora_weights(lora_model_id, weight_name=lora_filename)
+        lora_images = pipe(
+            prompt, output_type="np", generator=generator, num_inference_steps=num_inference_steps
+        ).images
+        lora_images = lora_images[0, -3:, -3:, -1].flatten()
+
+        pipe.unload_lora_weights()
+        generator = torch.manual_seed(0)
+        unloaded_lora_images = pipe(
+            prompt, output_type="np", generator=generator, num_inference_steps=num_inference_steps
+        ).images
+        unloaded_lora_images = unloaded_lora_images[0, -3:, -3:, -1].flatten()
+
+        self.assertFalse(np.allclose(initial_images, lora_images))
+        self.assertTrue(np.allclose(initial_images, unloaded_lora_images, atol=1e-3))