# FAQ¶

Frequently Asked Questions about pyhf and its use.

## Questions¶

### Is it possible to set the backend from the CLI?¶

Yes. Use the --backend option for pyhf cls to specify a tensor backend. The default backend is NumPy. For more information see pyhf cls --help.

## Troubleshooting¶

• import torch or import pyhf causes a Segmentation fault (core dumped)

This is may be the result of a conflict with the NVIDIA drivers that you have installed on your machine. Try uninstalling and completely removing all of them from your machine

# On Ubuntu/Debian
sudo apt-get purge nvidia*


and then installing the latest versions.