Just one data point that may be relevant -- blame shows the comment as dating from 2012.
The code for multiset partitions has changed since then. Before pull request 1658, by Chris Smith, multiset_partitions gave bad results. 1658 is from about the same time as the comment. Later, (pr 1848) I replaced Chris' implementation with a faster algorithm. The current ordering is deterministic, but I would be surprised if it were the same as the old algorithm. I don't claim any knowledge of Meijer integration, but I don't remember breaking any tests there. On Monday, March 23, 2015 at 11:21:04 AM UTC-7, Joachim Durchholz wrote: > > Hi all, > > this probably mostly goes to Tom Bachmann and Chris Smith, but maybe > others know a bit about Meijer integration. > > I'm working on something that changes the internal ordering of terms a > bit, and Meijer seems to rely on the current ordering for some > vaguely-explained benefits; I need to find out whether it's relevant or > not. > > Specifically, during > sympy/integrals/tests/test_integrals.py:test_issue_8368 , > I see a call to _rewrite2(f, x) with > f = Mul: exp(_x)*exp(-_x*s)/2 and > x = Dummy: _x > (it seems only f is relevant here). > > The docstring for _rewrite2 talks about multiset_partitions returning > stuff in a canonical (but not always optimal) order. Frustratingly, it > does not really explain what the problem is, nor what will fail if the > order is changed. > > It might be ultimately irrelevant though, as further processing filters > the result through ordered() in _rewrite2. If that's the case, then > maybe the docstring of _rewrite2 is wrong about test cases breaking, so > I'm unsure whether my current understanding of what's going on is > missing something important. > > Any tips, pointers and explanations appreciated. > > Regards, > Jo > -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/9ec0767e-b98c-44aa-a5e8-9ba03a63e3bd%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
