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
(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
> <javascript:>> wrote:
> > Forwarded to the correct list
> >
> > ---------- Forwarded message ----------
> > From: G. M.-S. <list...@gmail.com <javascript:>>
> > Date: Sun, Nov 22, 2015 at 4:34 PM
> > Subject: [sage-release] Bug in limit?
> > To: sage-r...@googlegroups.com <javascript:>
> >
> >
> >
> > 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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