if there's no "if shared_param.grad is not None: return" what will happen?

[yinqinghai]

        if shared_param.grad is not None:
            return
        shared_param._grad = param.grad

in this code, if there's no if shared_param.grad is not None: return shared_param._grad will be assigned each time? maybe just some performance loss?
maybe a stupid question, but i'm curious, thanks in advance.

[zhuzhu18]

我也感觉这个if语句没啥作用，每个子进程中的shared_model的梯度在zero_grad后都被置为None了，而且在进程之间还不共享