import torch import torch.distributed as dist def solution(local_hidden_states: torch.Tensor, local_weight: torch.Tensor, variance_epsilon: float) -> torch.Tensor: input_dtype = local_hidden_states.dtype # Upcast to float32 for stable variance calculation local_hidden_states = local_hidden_states.to(torch.float32) local_sum_squares = local_hidden_states.pow(2).sum(dim=-1, keepdim=True) dist.all_reduce(local_sum_squares, op=dist.ReduceOp.SUM) world_size = dist.get_world_size() global_hidden_size = local_hidden_states.shape[-1] * world_size variance = local_sum_squares / global_hidden_size local_hidden_states = local_hidden_states * torch.rsqrt(variance + variance_epsilon) return local_weight * local_hidden_states.to(input_dtype)