> kernelopts(opaquemodules=false):
> RD := Algebraic:-RecursiveDensePolynomials:
> p := 2^25-855:  # p := 2^62-923;
> m1 := z^2+z+1:
> m2 := y^4-y*z-2:
> m3 := x^2-x*y-4:
> m4 := w^2-3*w*x-y:
> R := ( [u,w,x,y,z], [m4,m3,m2,m1], p ):
> g := RD:-rpoly( u+2*w*z+5*x+4*y*z+3, R ):
> aa := RD:-rpoly( u+w*y+6*x+7*y*z+8, R ):
> bb := RD:-rpoly( u+w*x+9*w*z+2*y+2, R ):
> n := 3:  # 3, 4, 7, 15, 31, 61, 127
> a := RD:-mulrpoly(g,RD:-powrpoly(aa,n)):
> b := RD:-mulrpoly(g,RD:-powrpoly(bb,n)):
> CodeTools[Usage]( to 100 do h := RD:-gcdrpoly(a,b) od ):
memory used=2.12MiB, alloc change=0 bytes, cpu time=40.00ms, real time=41.00ms, gc time=0ns
> RD:-rpoly(h); # check
                          2 w z + 4 y z + u + 5 x + 3