Fix: prepare works even if nothing except tp specified (rare) (#3707)

src/accelerate/accelerator.py

@@ -1584,9 +1584,17 @@ class Accelerator:
         return result if len(result) > 1 else result[0]
 
     def _prepare_tp(self, *args):
+        # First pass: prepare everything except schedulers (and model, which is prepared separately below)
+        result = [
+            self._prepare_one(obj, first_pass=True) if not isinstance(obj, torch.nn.Module) else obj for obj in args
+        ]
+
+        # Second pass: prepare schedulers
+        result = [self._prepare_one(obj) if not isinstance(obj, torch.nn.Module) else obj for obj in result]
+
         device_mesh = self.torch_device_mesh
 
-        for arg in args:
+        for arg in result:
             if not isinstance(arg, torch.nn.Module):
                 continue