When composing a ``RingHomomorphism`` and an instance of ``RingHomomorphism_im_gens`` then the images of the generators are again checked for their validity, see rings/morphism.pyx:
def _composition_(self, right, homset): from sage.all import Rings if homset.homset_category().is_subcategory(Rings()): if isinstance(right, RingHomomorphism_im_gens): try: return homset([self(g) for g in right.im_gens()] .... I don't see any reason for performing this test again and it may take a lot of time depending on the implementation of _is_valid_homomorphism_. Is there anything I missed? Otherwise, I would just add ''check=False'' to the call. - Thomas -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-devel@googlegroups.com. Visit this group at http://groups.google.com/group/sage-devel?hl=en. For more options, visit https://groups.google.com/groups/opt_out.