Le jeudi 05 mai 2011 à 10:27 -0400, Haz a écrit : > Well as far as I understand the problems wrt caching and > assumptions in the current model are: > > 1) Assumptions are tied in at the lowest level of the core > (which apparently is a problem; I am just accepting that as a > fact of life for now). > 2) If we remove assumptions from objects entirely the cache > breaks down. (Apart from there not being a viable transition > strategy, as far as I see.) > 3) There are certain hacks to fix this like flushing the cache > aggressively, but they remain hacks. > 4) At any rate the cache causes lots of headaches and there > are calls for disabling it in general. > 5) But that won't work either because our performance depends > crucially on it for some computations. > > Having assumptions at a mix-in lower down in the algebra > hierarchy solves (1) [I think], avoids the trouble with (2) > and (3). Similarly having caching as a "mixin algebra" solves > (4) without the hacks of (5).
If you mean something like https://github.com/rlamy/sympy/tree/refactor-assumptions , it can be done, but doesn't buy us much. > So what is the issue with this solution: > - https://github.com/haz/sympy/commit/fb750ea49b963fa12d3a3e2dc833e53931050160 > > > I don`t see it as too hackish, since it simply shifts the use of the > cache from being always on to being used for a single calculation. The > solution in the branch from last year was indeed more of a hack > (flushed the cache whenever an assumption was added or removed from > the global assumption context). If the above solution is adopted, this > deals with 2-5 (as far as I can see). That's very much a hack. It makes top-level calls behave differently from inner calls, in a way that's hard to control. It's still wrong if assumptions change within a top-level call. And, since it uses global state, it'll break down completely in presence of threading (the rest of sympy isn't likely to be thread-safe either, though) or if an exception is raised. > The big questions that remain are those involving (1): it is > generally accepted that the old assumption system should give way to > the new one, but to what extent we remove the old ones from the core? > How the new ones replace the old ones? What is the syntax that we will > use for them? What "assumptions" will we make about the assumption > system? (i.e., local -vs- global context by default) > For the syntax, see http://code.google.com/p/sympy/issues/detail?id=2338 > I'm sorry I derailed the conversation into discussion on the cache > (I do feel that the above approach is appropriate). I think that the cache is a critical roadblock, so it's a good thing that we discuss it. -- 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.
