[GiNaC-devel] multivariate factorization (ginac/ginsh)

[Alexei Sheplyakov]

Hello,

On Sun, Feb 21, 2010 at 10:29:40AM +0100, Jens Vollinga wrote:

> ># The following seems to take forever:
> >
> >>t;
> >-E20^16*E4^8*E5^8*E1^16*q^4-(E10^24-E20^8*E5^16)*E4^16*E1^8+E2^24*E20^16*E5^8*q^4
> >>factor(t);
> >
> ># ctrl-C
> >  ginsh  815.46s user 3.39s system 94% cpu 14:26.22 total
> >
> >
> >Is the latter a huge-ish task or does ginac have a performance issue here?

> I ran the example and I get an exception! So, it seems there is a bug somewhere.

It looks like a bug in gcd routines.  Proof: try computing

gcd(expand(t), expand(diff(t, q)))

I'll try to find out what's going on here.


Best regards,
	Alexei