Yes, using the coercion, everything works fine. Thanks a lot for your help.
Nevertheless the commands are much slower than using just the polynomial ring and modding out afterwards. For a bigger example, I get 340 seconds for iterating with the quotient_ring methods whereas it takes less than 10 seconds for the mod-version (and this still is to slow for the really big examples I am interested in). Shouldn't the quotient_ring methods be faster, as SAGE is supposed to cut early on using the ideal relations to reduce higher powers? Seems the standard arithmetic is much more efficient and then modding out does not take too much time... Any ideas how to get faster code for the iterations? Best M. # a moderate example F.<a>=FiniteField(5) R.<t>=PolynomialRing(F) K.<z>=PolynomialRing(R) K2.<t,z>=PolynomialRing(F,2) Q2.<r,s>=K2.quotient_ring(K2.ideal([z^627,t^3126])) Q=(2*t^5-1)*z-z^6 QQ=Q2(Q) # the following loop takes about 340 seconds for i in range(6): QQ=Q(r,QQ) print i # the following only takes 8 seconds q=Q for i in range(6): q=q(t,Q).mod((z^627,t^3126)) print i -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org