On Tue, Jul 3, 2012 at 6:32 PM, Sergiu Ivanov <unlimitedscol...@gmail.com> wrote: > On Tue, Jul 3, 2012 at 4:03 PM, Matthew Rocklin <mrock...@gmail.com> wrote: >> I've found that sorting the args at creation time solves lots of problems. I >> have not found that this sorting causes any performance issues in SymPy. >> Sorting is fairly efficient and no one uses FiniteSets for huge sets. > > I will make the confession that it's not the first time that I think > that dropping initial element sorting in FiniteSet wasn't probably > that very cool an idea performance-wise.
I guess the time has come to bump this thread :-) I will remind the essence of the matter. Some time ago the constructor of FiniteSet has been modified to _not_ sort .args. This has created the necessity to explicitly sort FiniteSet's on many occasions. Currently, however, I have run in yet another occasion where arbitrary ordering of FiniteSet's comes in the way. FiniteSet relies on Basic.sort_key to construct the sort key. Basic.sort_key, in its turn, traverses .args and creates a sort key which _depends_ on the ordering of .args. I have stumbled over a situation where this actually influences how collections containing FiniteSet's are ordered. I really don't like the idea of sorting .args every time a sort key is required, and I have not managed to come up with a better way to approach the sort key problem. Therefore, there are basically two ways out: 1. Restore the old behaviour of FiniteSet, when it used to sort .args at creation, but rely on default_sort_key to sort the items instead of a custom function. 2. Invent a good way to create a compliant sort key independently of the ordering of .args. In support of (1) I would like to point out once again that the fact that a set is an unordered collection should normally be interpreted as an absence of guarantee of a certain ordering, rather then an prohibition to have any ordering. Sergiu -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to sympy@googlegroups.com. To unsubscribe from this group, send email to sympy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.
