On Thu, May 5, 2011 at 9:29 AM, Aaron Meurer <asmeu...@gmail.com> wrote: > On Thu, May 5, 2011 at 8:27 AM, Haz <christian.mu...@gmail.com> wrote: >>> 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). >> >> 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). >> 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) > > Well, one of the biggest problems with having the assumptions in the > core is that any time you want to edit the assumptions you have to > edit the core. Having them separate should make them much more > extensible. > > Also, maybe I am wrong, but I think it would be easier to have > something like Ask(expr, Q.whatever, Assume(x>y)) with the new system. > At any rate, this sort of things cannot be done with our current > is_assumption system (how do you assume x>y using that?).
I think that the biggest problem is that the assumptions are standing in the way to optimize the speed of the core. Ginac doesn't use any assumptions, neither does csympy (http://github.com/certik/csympy). Since Sage shows that it is not needed, we should follow the same route. And figure out some way to use assumptions in addition to the core somehow. Ondrej -- 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.
