[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).