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
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