[Distutils] PyPI is a sick sick hoarder

[Robert Collins]

On 16 May 2015 at 06:57, Robert Collins <robertc at robertcollins.net> wrote:
> So, I am working on pip issue 988: pip doesn't resolve packages at all.
>
> This is O(packages^alternatives_per_package): if you are resolving 10
...
> Scaling the number of packages is relatively easy; scaling the number
> of alternatives is harder. Even 300 packages (the dependency tree for
> openstack) is ~2.4T combinations to probe.

I added a check for the exact number (when the current step limit is hit):
Hit step limit during resolving,
22493640689038530013767184665222125808455708963348534886974974630893524036813561125576881299950281714638872640331745747555743820280235291929928862660035516365300612827387994788286647556890876840654454905860390366740480.000000
from 4038 versions in 205 packages after 100000 steps

Which indicates a alternatives factor of ~20. And AIUI PyPI has a long
tail itself, so its more common that folk will see > 5.7 factors,
rather than less common.

-Rob

-- 
Robert Collins <rbtcollins at hp.com>
Distinguished Technologist
HP Converged Cloud