ensure torch always up-to-date in CI

[epwalsh]

This adds a step in CI that will ensure the current installed version of PyTorch is the most recent allowed version PyTorch according to our dependency specification in setup.py.

This is needed because we have to hard-code the torch installation steps in some places, so dependabot updates don't necessarily change the version of PyTorch used in CI.

[dirkgr]

Is there no pip incantation that can do this? It seems brittle to parse the torch version string like that.

[epwalsh]

Is there no pip incantation that can do this? It seems brittle to parse the torch version string like that.

Another option would be to parse the output of pip show torch or pip freeze | grep torch. But that seems even more brittle.

[dirkgr]

What I mean is, isn't there a pip incantation that can install the highest allowed version of torch? Does pip install torch --upgrade do it?

[epwalsh]

That works with any other dependency but not with torch since the exact version we need depends on the CUDA version available, and pip is not aware of that.

[dirkgr]

Well, I'm not excited about the brittleness, but I don't have a better idea either.

[dirkgr]

Well what do you know, it broke.