def METHOD_NAME(self):
    """
    Move gradients from GPU to CPU.
    """
    self.cpu_grad = torch.empty(self.param_num, dtype=torch.half, pin_memory=True)
    self.cpu_grad.copy_(self.fp16_data[:self.param_num], non_blocking=True)
    self.fp16_data.record_stream(torch.cuda.current_stream())
    if not self.in_mem_pool_flag:
        self.free_cuda_data()
    self.grad_num = 0