feat: GPU detection + PHOTO_JUDGERS_DEVICE override + diagnostics

src/scorers/laion.py

@@ -68,7 +68,26 @@ class LaionScorer:
         self.head = None  # type: ignore[assignment]
         self._version = "v2"
         self._cache_dir = cache_dir
-        self._device = "cuda" if torch.cuda.is_available() else "cpu"
+        self._device = self._pick_device()
+
+    @staticmethod
+    def _pick_device() -> str:
+        """Select CUDA GPU when available; allow override via env var.
+
+        Priority: PHOTO_JUDGERS_DEVICE env var -> cuda (if available) -> cpu.
+        """
+        override = os.environ.get("PHOTO_JUDGERS_DEVICE", "").strip().lower()
+        if override:
+            print(f"  Device overridden by PHOTO_JUDGERS_DEVICE: {override}")
+            return override
+
+        cuda_ok = torch.cuda.is_available()
+        print(f"  torch.cuda.is_available(): {cuda_ok}")
+        if cuda_ok:
+            print(f"  Using GPU: {torch.cuda.get_device_name(0)}")
+            return "cuda"
+        print("  Using CPU (CUDA not available to torch).")
+        return "cpu"
 
     def _head_path(self) -> str:
         return os.path.join(self._cache_dir, self.HEAD_FILENAME)