interrogate: Fix CLIP-interrogation on CPU

Currently, trying to perform CLIP interrogation on a CPU fails, saying:

```
RuntimeError: "slow_conv2d_cpu" not implemented for 'Half'
```

This merge request fixes this issue by detecting whether the target
device is CPU and, if so, force-enabling `--no-half` and passing
`device="cpu"` to `clip.load()` (which then does some extra tricks to
ensure it works correctly on CPU).

modules/interrogate.py

@@ -28,9 +28,11 @@ class InterrogateModels:
     clip_preprocess = None
     categories = None
     dtype = None
+    running_on_cpu = None
 
     def __init__(self, content_dir):
         self.categories = []
+        self.running_on_cpu = devices.device_interrogate == torch.device("cpu")
 
         if os.path.exists(content_dir):
             for filename in os.listdir(content_dir):
@@ -53,7 +55,11 @@ class InterrogateModels:
     def load_clip_model(self):
         import clip
 
-        model, preprocess = clip.load(clip_model_name)
+        if self.running_on_cpu:
+            model, preprocess = clip.load(clip_model_name, device="cpu")
+        else:
+            model, preprocess = clip.load(clip_model_name)
+
         model.eval()
         model = model.to(devices.device_interrogate)
 
@@ -62,14 +68,14 @@ class InterrogateModels:
     def load(self):
         if self.blip_model is None:
             self.blip_model = self.load_blip_model()
-            if not shared.cmd_opts.no_half:
+            if not shared.cmd_opts.no_half and not self.running_on_cpu:
                 self.blip_model = self.blip_model.half()
 
         self.blip_model = self.blip_model.to(devices.device_interrogate)
 
         if self.clip_model is None:
             self.clip_model, self.clip_preprocess = self.load_clip_model()
-            if not shared.cmd_opts.no_half:
+            if not shared.cmd_opts.no_half and not self.running_on_cpu:
                 self.clip_model = self.clip_model.half()
 
         self.clip_model = self.clip_model.to(devices.device_interrogate)