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 packages with 10 versions each, there are approximately 10^10 or 10G combinations. 10 packages with 100 versions each - 10^100.
So - its going to depend pretty heavily on some good heuristics in whatever final algorithm makes its way in, but the problem is exacerbated by PyPI's nature. Most Linux (all that i'm aware of) distributions have at most 5 versions of a package to consider at any time - installed(might be None), current release, current release security updates, new release being upgraded to, new release being upgraded to's security updates. And their common worst case is actually 2 versions: installed==current release and one new release present. They map alternatives out into separate packages (e.g. when an older soname is deliberately kept across an ABI incompatibility, you end up with 2 packages, not 2 versions of one package). To when comparing pip's challenge to apt's: apt has ~20-30K packages, with altnernatives ~= 2, or pip has ~60K packages, with alternatives ~= 5.7 (I asked dstufft) 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 wonder if it makes sense to give some back-pressure to people, or at the very least encourage them to remove distributions that: - they don't support anymore - have security holes If folk consider PyPI a sort of historical archive then perhaps we could have a feature to select 'supported' versions by the author, and allow a query parameter to ask for all the versions. -Rob -- Robert Collins <rbtcoll...@hp.com> Distinguished Technologist HP Converged Cloud _______________________________________________ Distutils-SIG maillist - Distutils-SIG@python.org https://mail.python.org/mailman/listinfo/distutils-sig
