How to install pytorch with RTX 3080

Dear Sir/Madam,

I first install cuda 11.1 and then install the torch by running the script “pip3 install --pre torch==1.4 torchvision -f”. After that, I import cuda and try to run “a=torch.randn(1,4).cuda()” but it hangs.

By the way, my system is Ubuntu 18.04 and python version is 3.7.5.