mesh_dim_names
Two changes: 1. Require `mesh_dim_names` if using HSDP 2. Pass only the shard mesh to `fsdp_pre_all_gather` Change 1 is technically BC breaking, but it should not be hard to fix on the user side. Pull Request resolved: https://github.com/pytorch/pytorch/pull/137436 Approved by: https://github.com/weifengpy, https://github.com/wz337
shard_placement_fn