Re: [Maxima-discuss] simplify_sum leads to a wrong value

[philippe <rou...@gm...>]

Thanks for your reply Robert.

Le 11/04/2020 à 22:57, Robert Dodier a écrit :
> 
> Hmm, I don't know where simplify_sum went off the tracks. I didn't look
> carefully at what simplify_sum is doing, but if I understand correctly
> one of the major algorithms it employs is the Zeilberger/Gosper
> algorithm which works, from what I understand, on summands which are
> rational functions. I speculate that it's the sin(k*%pi/3) which causes
> trouble, but that's just a guess.

this problems looks for me equivalent to problems arising when combining
taylor series of functions involving (-1)^n terms or only even/odd
terms.  Could we  build a mecanism that converts a series :

sum(an,n,0,inf)-> sum(sum(a[q*n+k],n,1,inf,k,0,q-1)

so that a[q*n+k] will be a rational in q,n,k  ?

> [...]
> 
> It's still a bug that simplify_sum (or maybe some other simplification
> step, I dunno) handled the original summation incorrectly. Maybe someone
> will create a bug report about it.

do you want me to report it on https://sourceforge.net/p/maxima/bugs/

Best regards
Philippe