On Thu, Aug 20, 2009 at 4:11 AM, Golam Mortuza
Hossain<gmhoss...@gmail.com> wrote:
>
> Hi,
>
> It takes too long to check whether x is in a list in new symbolics
>
> ---------
> sage: var('x,x1,x2,x3,x4')
> (x, x1, x2, x3, x4)
> sage: f = function('f')
> sage: mylist = [x1,x2,x3,x4,f(x1),f(x2),f(x3),f(x4)]
>
> sage: timeit('x in mylist')
> 5 loops, best of 3: 461 ms per loop
> --------
>
> If your program needs to check it couple of more times
> ----------
> sage: timeit('x in mylist')
> 5 loops, best of 3: 1.26 s per loop
> sage: timeit('x in mylist')
> 5 loops, best of 3: 3.4 s per loop
> ----------
>
> For a comparison
> ---------
> sage: timeit('x1 in mylist')
> 625 loops, best of 3: 473 ns per loop
> ---------
>
> Reason for this huge discrepancy stems from the fact that
> except for last example, in all previous cases maxima is called
> to check the equality.
>
> Thus it seems, new symbolics depends on maxima for basic
> operations even now.
>
> I don't know the rationale behind this design given pynac has
> a method to compare two symbolic expression (ex1.is_equal(ex2)).
>
> In any case, this design ensures writing a program in new symbolics
> where some basic tests like "if x in list" needs to done, is no better than
> old symbolics.
>
That's not for any list, but it is for the one you constructed. I
think to get the new symbolics out at some point we finally gave in
and made the compare method fall back to Maxima (in case several
pynac-based methods failed) so that massive amounts of user code and
doctests wouldn't break. Fixing this is obviously something that
needs to be done. Hopefully you will do it! :-)
William
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