Return type:
      Future[Tensor]
torch.distributed.algorithms.ddp_comm_hooks.default_hooks.fp16_compress_hook(process_group, bucket)
This DDP communication hook implements a simple gradient
   compression approach that casts "GradBucket" tensor to half-
   precision floating-point format ("torch.float16") and then divides
   it by the process group size. It allreduces those "float16"
   gradient tensors. Once compressed gradient tensors are allreduced,
   the chained callback "decompress" casts it back to the input data
   type (such as "float32").
Example::
      >>> ddp_model.register_comm_hook(process_group, fp16_compress_hook)
Return type:
      Future[Tensor]
torch.distributed.algorithms.ddp_comm_hooks.default_hooks.bf16_compress_hook(process_group, bucket)
Warning: This API is experimental, and it requires NCCL version
   later than 2.9.6.
This DDP communication hook implements a simple gradient
   compression approach that casts "GradBucket" tensor to half-