[CLN-list] multivariate factorization (ginac/ginsh)

[Joerg Arndt]

[could someone please forward to ginac-devel, I am
 not subscribed there]


Within ginsh:

> ?factor
factor(expression) - factorizes an expression (univariate)

# but it appears to do multivariate factorization as well:

> t=(E20^16*E5^8*q^4*E2^24 + (-E20^16*E5^8*q^4*E4^8*E1^16));
-E1^16*q^4*E20^16*E4^8*E5^8+q^4*E2^24*E20^16*E5^8
> factor(t);
-(E1^2*E4-E2^3)*q^4*(E2^12+E1^8*E4^4)*E20^16*E5^8*(E1^2*E4+E2^3)*(E2^6+E1^4*E4^2)


# 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 stepped on this one because sage had the very same issue.
I suggested to use ginac for multivariate factorization,
then found ginac itself takes quite long (so they may already
be using ginac).