Added --partition argument and adjusted node & GPU name parsing to work on our cluster

[talesa]

By default 30 chars were too short to print some of our node names, increased the limit.

Some of our GPUs had weird names, changed the way it's parsed to a regexp, added examples of some weird outputs I got on some nodes to the following website where people contributing can keep iterating on the regexp used to cover other weird strings they encounter.
https://regex101.com/r/RHYM8Z/3

[frankier]

This PR makes it almost work for me in ARC, but I had another problem afterwards. Sometimes we get tokens as:

tokens ['gpu', 'arcus-htc-***, ***, ***]

In which case we can't get num_gpus. I'm not sure what the solution is here. Should num_gpus be assumed to be 1?

[talesa]

I've never used ARC so I don't know how the output is formatted there or how many GPUs per node are there.

[albanie]

@talesa - thanks a lot for this!
@frankier, would you be able to paste input/output samples (so I can check that the PR doesn't break stuff for you) when merging?

[frankier]

So the situation is that I'm +1 merging this PR because it makes this script go from not working -> almost working for me. What makes it work for me is adding also the following, which just throws away rows without a number of GPU specified. However, this isn't going to produce an accurate result probably, since it throws away data. If you merge the PR, then I can go ahead an put this in a more detailed new issue if/when I can replicate it.

*** slurm_gpustat.py.1	2020-12-14 06:40:58.643007000 +0000
--- slurm_gpustat.py	2020-11-30 14:03:42.053292000 +0000
***************
*** 527,536 ****
--- 527,538 ----
          # ignore pending jobs
          if len(tokens) < 4 or not tokens[0].startswith("gpu"):
              continue
          gpu_count_str, node_str, user, jobid = tokens
          gpu_count_tokens = gpu_count_str.split(":")
+         if len(gpu_count_tokens) == 1:
+             continue
          num_gpus = int(gpu_count_tokens[-1])
          if len(gpu_count_tokens) == 2:
              gpu_type = None
          elif len(gpu_count_tokens) == 3:
              gpu_type = gpu_count_tokens[1]