On Tue, Nov 6, 2018 at 8:35 AM Waldek Hebisch <hebi...@math.uni.wroc.pl> wrote: > > > earlier patch. Here is a revised patch that corrects this problem. > > (Only one additional change at the beginning.) > > I have tried: > > h3 := x*y*z - x*z*y + z*x*y - z*y*x + y*z*x - y*x*z > factor(h3*h3) > > and after about hour I did not get answer. >
Yes. This is a good example where the heuristic fails. > Since nobody seems to be interested in coding Davenport method > I did that. At > > http://www.math.uni.wroc.pl/~hebisch/fricas/dcfact.input > http://www.math.uni.wroc.pl/~hebisch/fricas/nc_ini04b.input > > dcfact.input is actual routine. nc_ini04b.input defines needed > types. With that things like > > h2 := x*y - y*x > homo_fact(h2*h3*h2*h3*h2) > > work. > Thanks, that is very nice. And it is impressively fast on all the examples I tried. However it did find this example where homo_fact fails to find a factorization: (110) -> factor((x^2-1)^2) (110) [1 - x, 1 - x, 1 + x, 1 + x] Type: List(XDistributedPolynomial(OrderedVariableList([x,y,z,w,x1,x2,x3,x4,x5]),Integer)) Time: 0.44 (EV) + 0.01 (OT) = 0.45 sec (111) -> homo_fact((x^2-1)^2) 2 4 (111) [1 - 2 x + x ] Type: List(XDistributedPolynomial(OrderedVariableList([x,y,z,w,x1,x2,x3,x4,x5]),Integer)) Time: 0.00 (IN) + 0.00 (OT) = 0.00 sec -- It is also interesting to compare the results obtained by Konrad Schrempf's algorithm. (Start with 'nc_ini14.input' from the ncpoly repository.) -- You received this message because you are subscribed to the Google Groups "FriCAS - computer algebra system" group. To unsubscribe from this group and stop receiving emails from it, send an email to fricas-devel+unsubscr...@googlegroups.com. To post to this group, send email to fricas-devel@googlegroups.com. Visit this group at https://groups.google.com/group/fricas-devel. For more options, visit https://groups.google.com/d/optout.
