Print fqn in the warning message (#94313)

zhaojuanmao · pytorchmergebot · commit e0c24ec2a5db · 2023-02-08T06:45:53.000Z
Print fqn in the warning message, also make "else" match with the "if" in _apply_to_modules() Pull Request resolved: #94313 Approved by: https://github.com/fegin
diff --git a/torch/distributed/fsdp/_common_utils.py b/torch/distributed/fsdp/_common_utils.py
@@ -280,10 +280,12 @@ def f(module: torch.nn.Module, prefix: str, *args, **kwargs):
                             break
                     else:
                         # TODO: Remove this hack once DMP + FSDP is not supported.
+                        first_fqn = next(iter(filter_fqns), "")
                         warnings.warn(
                             "An unexpected prefix is detected. "
                             "This case should only happen when using "
                             "DistributedModelParallel with FullyShardedDataParallel."
+                            f"one fqn: {first_fqn}"
                         )
                         new_prefix = prefix
                 f(submodule, new_prefix, *args, **kwargs)
