add fp16 support to controlnet models

Author: Lincoln Stein

invokeai/backend/model_management/models/controlnet.py

@@ -1,8 +1,7 @@
 import os
 import torch
 from enum import Enum
-from pathlib import Path
-from typing import Optional, Union, Literal
+from typing import Optional
 from .base import (
     ModelBase,
     ModelConfigBase,
@@ -14,6 +13,7 @@
     calc_model_size_by_data,
     classproperty,
     InvalidModelException,
+    ModelNotFoundException,
 )
 
 class ControlNetModelFormat(str, Enum):
@@ -60,10 +60,20 @@ def get_model(
         if child_type is not None:
             raise Exception("There is no child models in controlnet model")
 
-        model = self.model_class.from_pretrained(
-            self.model_path,
-            torch_dtype=torch_dtype,
-        )
+        model = None
+        for variant in ['fp16',None]:
+            try:
+                model = self.model_class.from_pretrained(
+                    self.model_path,
+                    torch_dtype=torch_dtype,
+                    variant=variant,
+                )
+                break
+            except:
+                pass
+        if not model:
+            raise ModelNotFoundException()
+        
         # calc more accurate size
         self.model_size = calc_model_size_by_data(model)
         return model