#11990: infinite sums that are infinite produce errors
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Reporter: dkrenn | Owner: burcin
Type: defect | Status: new
Priority: major | Milestone: sage-5.4
Component: calculus | Resolution:
Keywords: infinite sums, infinite, maxima | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by kcrisman):
> If we know that a sum diverge monotonically to infinity, then the output
should say that, i.e. should be {{{oo}}}.
Well, that is the question.
> The reason I open the ticket is, that all sums above have the same
behavior, but the output is always different, which should not be.
Well, `maxima.sum` is not really applicable, because that is a Maxima
element. That's sort of like complaining that mpmath returns `mpf`
numbers - you aren't asking for a Sage element. So it still sort of
reverts to the big question.
> And, I don't see (from a user point of view) any reason, that in
> {{{
> sum(m, m, 0, oo)
> }}}
> Sage asks "Is m positive or zero?" and in
I'll note that now Sage (via Maxima) asks "Is m positive, negative, or
zero?"
> {{{
> sum(2^m, m, 0, oo)
> }}}
> not.
Right, as I said in comment:1, there are lots of things like this in
Maxima (extra interactions). We can report it upstream, but it may be
that the algorithm they use just has to ask this.
It sounds like you're motivated on this one, and certainly it would be
great to get the right error and not the question.
{{{
(%i6) load(simplify_sum);
(%o6) /Users/.../sage-5.2/local/share/maxima/5.26.0/share/c\
ontrib/solve_rec/simplify_sum.mac
(%i7) simplify_sum(sum(m,m,0,inf));
Is m positive, negative, or zero?
(%i3) assume(m>0);
(%o3) [m > 0]
(%i4) simplify_sum(sum(m,m,0,inf));
sum: sum is divergent.
#0: simplify_sum(expr='sum(m,m,0,inf))
-- an error. To debug this try: debugmode(true);
}}}
You could ask about this on the Maxima list or report it on their tracker!
Incidentally,
{{{
sage: var('m')
m
sage: assume(m>0)
sage: sum(m,m,0,oo)
ValueError: Sum is divergent.
}}}
so something must have changed in the meantime.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11990#comment:6>
Sage <http://www.sagemath.org>
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