On Mon, Nov 23, 2015 at 12:17 PM, Dima Pasechnik <dimp...@gmail.com> wrote:
>
>
> On Monday, 23 November 2015 19:38:39 UTC, Ondrej Certik wrote:
>>
>> On Mon, Nov 23, 2015 at 12:20 PM, Dima Pasechnik <dim...@gmail.com> wrote:
>> >
>> >
>> > On Monday, 23 November 2015 00:43:02 UTC, William wrote:
>> >>
>> >> This definitely looks like a bug. In the meantime, a workaround is to
>> >> use sympy:
>> >>
>> >> sage: var('m a0')
>> >> (m, a0)
>> >> sage: x=2/5*((3/4)^m - 1)*(a0 - 1000000) + 1/5*(3*(3/4)^m + 2)*a0;x
>> >> 2/5*((3/4)^m - 1)*(a0 - 1000000) + 1/5*(3*(3/4)^m + 2)*a0
>> >> sage: limit(x, m=oo)
>> >> [BAD]
>> >> sage: limit(x, m=oo, algorithm='sympy')
>> >> 4000000
>> >>
>> >> I wonder -- to what extent should we be using maxima by default still
>> >> for limits, instead of sympy...? At some point, presumably sympy will
>> >> be uniformly better than maxima?
>> >
>> >
>> > the bug is not really in maxima, it's in Sage's interface to maxima:
>> >
>> > (%i7) limit(2/5*((3/4)^m - 1)*(a0 - 1000000) + 1/5*(3*(3/4)^m +
>> > 2)*a0,m,inf);
>> > (%o7) 400000
>>
>> Note that William's result has one more zero in the answer... Which
>> one is correct?
>
>
> one doesn't need a computer here :)
> lim_{m->oo} 2/5*((3/4)^m - 1)*(a0 - 1000000) + 1/5*(3*(3/4)^m + 2)*a0 =
> 2/5*(0 - 1)*(a0 - 10^6) + 1/5*(0 + 2)*a0=2*10^6/5 = 400000
>
> I don't know where extra 0 came from, I get the same answer as maxima or my
> pen:
Copy/paste error. I gave a link to the actual session where everything is fine.
William
>
> sage: x=2/5*((3/4)^m - 1)*(a0 - 1000000) + 1/5*(3*(3/4)^m + 2)*a0;x
> 2/5*((3/4)^m - 1)*(a0 - 1000000) + 1/5*(3*(3/4)^m + 2)*a0
> sage: limit(x, m=oo, algorithm="sympy")
> 400000
>
> Dima
>>
>>
>> Ondrej
>>
>> >
>> > (this is with 'sage --maxima')
>> > probably extra maxima packages loaded along with maxima cause this OOM
>> > in
>> > Sage.
>> >
>> >
>> >>
>> >>
>> >> Public worksheet:
>> >>
>> >>
>> >>
>> >> https://cloud.sagemath.com/projects/4a5f0542-5873-4eed-a85c-a18c706e8bcd/files/support/2015-11-22-163829-limit.sagews
>> >>
>> >> On Sun, Nov 22, 2015 at 2:00 PM, David Joyner <wdjo...@gmail.com>
>> >> wrote:
>> >> > Forwarded to the correct list
>> >> >
>> >> > ---------- Forwarded message ----------
>> >> > From: G. M.-S. <list...@gmail.com>
>> >> > Date: Sun, Nov 22, 2015 at 4:34 PM
>> >> > Subject: [sage-release] Bug in limit?
>> >> > To: sage-r...@googlegroups.com
>> >> >
>> >> >
>> >> >
>> >> > Hello.
>> >> >
>> >> > This is my first post, please be indulgent.
>> >> >
>> >> > Is the following a bug?
>> >> >
>> >> > Thanks in advance.
>> >> >
>> >> > Guillermo Moreno-Socías
>> >> >
>> >> >
>> >> > ┌────────────────────────────────────────────────────────────────────┐
>> >> > │ SageMath Version 6.9, Release Date: 2015-10-10
>> >> > │
>> >> > │ Type "notebook()" for the browser-based notebook interface.
>> >> > │
>> >> > │ Type "help()" for help.
>> >> > │
>> >> >
>> >> > └────────────────────────────────────────────────────────────────────┘
>> >> > sage: var('m a0')
>> >> > (m, a0)
>> >> > sage: x=2/5*((3/4)^m - 1)*(a0 - 1000000) + 1/5*(3*(3/4)^m + 2)*a0;x
>> >> > 2/5*((3/4)^m - 1)*(a0 - 1000000) + 1/5*(3*(3/4)^m + 2)*a0
>> >> > sage: limit(x,m=oo)
>> >> >
>> >> > ;;;
>> >> > ;;; Detected access to protected memory, also kwown as 'bus or
>> >> > segmentation fault'.
>> >> > ;;; Jumping to the outermost toplevel prompt
>> >> > ;;;
>> >> >
>> >> > (Note that if x is expanded then the limit is correctly calculated.)
>> >> >
>> >> > --
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>> >>
>> >>
>> >>
>> >> --
>> >> William (http://wstein.org)
>> >
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