[From single file] Make accelerate optional (#4132)

* Make accelerate optional

* make accelerate optional

src/diffusers/pipelines/stable_diffusion/convert_from_ckpt.py

@@ -15,6 +15,7 @@
 """ Conversion script for the Stable Diffusion checkpoints."""
 
 import re
+from contextlib import nullcontext
 from io import BytesIO
 from typing import Optional
 
@@ -779,7 +780,8 @@ def convert_ldm_clip_checkpoint(checkpoint, local_files_only=False, text_encoder
         config_name = "openai/clip-vit-large-patch14"
         config = CLIPTextConfig.from_pretrained(config_name)
 
-        with init_empty_weights():
+        ctx = init_empty_weights if is_accelerate_available() else nullcontext
+        with ctx():
             text_model = CLIPTextModel(config)
 
     keys = list(checkpoint.keys())
@@ -793,8 +795,11 @@ def convert_ldm_clip_checkpoint(checkpoint, local_files_only=False, text_encoder
             if key.startswith(prefix):
                 text_model_dict[key[len(prefix + ".") :]] = checkpoint[key]
 
+    if is_accelerate_available():
         for param_name, param in text_model_dict.items():
             set_module_tensor_to_device(text_model, param_name, "cpu", value=param)
+    else:
+        text_model.load_state_dict(text_model_dict)
 
     return text_model
 
@@ -900,7 +905,8 @@ def convert_open_clip_checkpoint(
     # )
     config = CLIPTextConfig.from_pretrained(config_name, **config_kwargs)
 
-    with init_empty_weights():
+    ctx = init_empty_weights if is_accelerate_available() else nullcontext
+    with ctx():
         text_model = CLIPTextModelWithProjection(config) if has_projection else CLIPTextModel(config)
 
     keys = list(checkpoint.keys())
@@ -950,8 +956,11 @@ def convert_open_clip_checkpoint(
 
                 text_model_dict[new_key] = checkpoint[key]
 
+    if is_accelerate_available():
         for param_name, param in text_model_dict.items():
             set_module_tensor_to_device(text_model, param_name, "cpu", value=param)
+    else:
+        text_model.load_state_dict(text_model_dict)
 
     return text_model
 
@@ -1172,11 +1181,6 @@ def download_from_original_stable_diffusion_ckpt(
         StableUnCLIPPipeline,
     )
 
-    if not is_accelerate_available():
-        raise ImportError(
-            "To correctly use `from_single_file`, please make sure that `accelerate` is installed. You can install it with `pip install accelerate`."
-        )
-
     if pipeline_class is None:
         pipeline_class = StableDiffusionPipeline
 
@@ -1346,15 +1350,19 @@ def download_from_original_stable_diffusion_ckpt(
     # Convert the UNet2DConditionModel model.
     unet_config = create_unet_diffusers_config(original_config, image_size=image_size)
     unet_config["upcast_attention"] = upcast_attention
-    with init_empty_weights():
-        unet = UNet2DConditionModel(**unet_config)
-
     converted_unet_checkpoint = convert_ldm_unet_checkpoint(
         checkpoint, unet_config, path=checkpoint_path, extract_ema=extract_ema
     )
 
+    ctx = init_empty_weights if is_accelerate_available() else nullcontext
+    with ctx():
+        unet = UNet2DConditionModel(**unet_config)
+
+    if is_accelerate_available():
         for param_name, param in converted_unet_checkpoint.items():
             set_module_tensor_to_device(unet, param_name, "cpu", value=param)
+    else:
+        unet.load_state_dict(converted_unet_checkpoint)
 
     # Convert the VAE model.
     if vae_path is None:
@@ -1372,11 +1380,15 @@ def download_from_original_stable_diffusion_ckpt(
 
         vae_config["scaling_factor"] = vae_scaling_factor
 
-        with init_empty_weights():
+        ctx = init_empty_weights if is_accelerate_available() else nullcontext
+        with ctx():
             vae = AutoencoderKL(**vae_config)
 
+        if is_accelerate_available():
             for param_name, param in converted_vae_checkpoint.items():
                 set_module_tensor_to_device(vae, param_name, "cpu", value=param)
+        else:
+            vae.load_state_dict(converted_vae_checkpoint)
     else:
         vae = AutoencoderKL.from_pretrained(vae_path)