fix

Author: tastelikefeet

swift/cli/utils.py

@@ -4,6 +4,9 @@
 def try_use_single_device_mode():
     if os.environ.get('SWIFT_SINGLE_DEVICE_MODE', '0') == '1':
         visible_devices = os.environ['CUDA_VISIBLE_DEVICES'].split(',')
-        visible_device = visible_devices[int(os.environ['LOCAL_RANK'])]
+        local_rank = os.environ.get('LOCAL_RANK')
+        if local_rank is None or not visible_devices:
+            return
+        visible_device = visible_devices[int(local_rank)]
         os.environ['CUDA_VISIBLE_DEVICES'] = str(visible_device)
         os.environ['LOCAL_RANK'] = '0'