Barinder, I'll look into this (tomorrow) -- it's my code. Please open
a ticket and CC me. It's happening in the code to reduce a model with
respect to scaling by units.
John
On Tue, 12 Jul 2022 at 16:19, Barinder Banwait <b.s.banwai...@gmail.com> wrote:
>
> Dear sage-devel,
>
> I am running into an issue with computing isogeny classes of elliptic curves
> over number fields.
>
> Here is what I entered:
>
> K.<a> = QuadraticField(4569)
> myJ = 46969655/32768
> E = EllipticCurve(j=K(myJ))
> C = E.isogeny_class()
>
> This raises a KeyError in the first instance, which seems to be handled via a
> direct call to IsogenyClass_EC_NumberField, but this then raises a
> ValueError: Cannot convert infinity or NaN to Sage Integer. The full stack
> trace is in the PS.
>
> This error has occurred on sage-9.4 on a system whose `uname -a` is `Linux
> LEGENDRE 5.4.0-91-generic #102-Ubuntu SMP Fri Nov 5 16:31:28 UTC 2021 x86_64
> x86_64 x86_64 GNU/Linux`, as well as on sage-9.7-beta5 on `Linux Barinder
> 5.4.0-121-generic #137-Ubuntu SMP Wed Jun 15 13:33:07 UTC 2022 x86_64 x86_64
> x86_64 GNU/Linux`.
>
> Changing the field K to many other quadratic fields does not yield any error.
> However I did also notice this error with many j-invariants in
> QuadraticField(6537), so it somehow seems to be base-field dependent.
>
> Best wishes,
> Barinder
>
> PS. Full traceback:
>
> ---------------------------------------------------------------------------
> KeyError Traceback (most recent call last)
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/structure/category_object.pyx
> in sage.structure.category_object.CategoryObject.getattr_from_category
> (build/cythonized/sage/structure/category_object.c:7074)()
> 838 try:
> --> 839 return self.__cached_methods[name]
> 840 except KeyError:
>
> KeyError: '_isoclass'
>
> During handling of the above exception, another exception occurred:
>
> AttributeError Traceback (most recent call last)
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/schemes/elliptic_curves/ell_number_field.py
> in isogeny_class(self, reducible_primes, algorithm, minimal_models)
> 3007 try:
> -> 3008 return self._isoclass
> 3009 except AttributeError:
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/structure/category_object.pyx
> in sage.structure.category_object.CategoryObject.__getattr__
> (build/cythonized/sage/structure/category_object.c:6993)()
> 832 """
> --> 833 return self.getattr_from_category(name)
> 834
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/structure/category_object.pyx
> in sage.structure.category_object.CategoryObject.getattr_from_category
> (build/cythonized/sage/structure/category_object.c:7159)()
> 847
> --> 848 attr = getattr_from_other_class(self, cls, name)
> 849 self.__cached_methods[name] = attr
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/cpython/getattr.pyx
> in sage.cpython.getattr.getattr_from_other_class
> (build/cythonized/sage/cpython/getattr.c:2552)()
> 366 dummy_error_message.name = name
> --> 367 raise AttributeError(dummy_error_message)
> 368 cdef PyObject* attr = instance_getattr(cls, name)
>
> AttributeError: 'sage.sets.pythonclass.Set_PythonType_class' object has no
> attribute '_Hom_'
>
> During handling of the above exception, another exception occurred:
>
> ValueError Traceback (most recent call last)
> <ipython-input-1-a9c20a51d066> in <module>
> 2 myJ = Integer(46969655)/Integer(32768)
> 3 E = EllipticCurve(j=K(myJ))
> ----> 4 C = E.isogeny_class()
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/schemes/elliptic_curves/ell_number_field.py
> in isogeny_class(self, reducible_primes, algorithm, minimal_models)
> 3009 except AttributeError:
> 3010 from sage.schemes.elliptic_curves.isogeny_class import
> IsogenyClass_EC_NumberField
> -> 3011 self._isoclass = IsogenyClass_EC_NumberField(self,
> reducible_primes=reducible_primes, algorithm=algorithm,
> minimal_models=minimal_models)
> 3012 return self._isoclass
> 3013
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/schemes/elliptic_curves/isogeny_class.py
> in __init__(self, E, reducible_primes, algorithm, minimal_models)
> 705 self._algorithm = algorithm
> 706 self._minimal_models = minimal_models
> --> 707 IsogenyClass_EC.__init__(self, E, label=None, empty=False)
> 708
> 709 def copy(self):
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/schemes/elliptic_curves/isogeny_class.py
> in __init__(self, E, label, empty)
> 68 self._label = label
> 69 if not empty:
> ---> 70 self._compute()
> 71
> 72 def __len__(self):
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/schemes/elliptic_curves/isogeny_class.py
> in _compute(self, verbose)
> 789 sys.stdout.write(" possible isogeny degrees: %s" % degs)
> 790 sys.stdout.flush()
> --> 791 isogenies = E.isogenies_prime_degree(degs,
> minimal_models=self._minimal_models)
> 792 if verbose:
> 793 sys.stdout.write(" -actual isogeny degrees: %s" %
> Set(phi.degree() for phi in isogenies))
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/schemes/elliptic_curves/ell_number_field.py
> in isogenies_prime_degree(self, l, algorithm, minimal_models)
> 3108 return self.isogenies_prime_degree(L,
> minimal_models=minimal_models)
> 3109
> -> 3110 isogs = sum([self.isogenies_prime_degree(p,
> minimal_models=minimal_models) for p in l],
> 3111 [])
> 3112
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/schemes/elliptic_curves/ell_number_field.py
> in <listcomp>(.0)
> 3108 return self.isogenies_prime_degree(L,
> minimal_models=minimal_models)
> 3109
> -> 3110 isogs = sum([self.isogenies_prime_degree(p,
> minimal_models=minimal_models) for p in l],
> 3111 [])
> 3112
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/schemes/elliptic_curves/ell_number_field.py
> in isogenies_prime_degree(self, l, algorithm, minimal_models)
> 3097 try:
> 3098 if l.is_prime(proof=False):
> -> 3099 return isogenies_prime_degree(self, l,
> minimal_models=minimal_models)
> 3100 else:
> 3101 raise ValueError("%s is not prime." % l)
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/schemes/elliptic_curves/isogeny_small_degree.py
> in isogenies_prime_degree(E, l, minimal_models)
> 2340 return isogenies_2(E, minimal_models=minimal_models)
> 2341 if l==3:
> -> 2342 return isogenies_3(E, minimal_models=minimal_models)
> 2343
> 2344 p = E.base_ring().characteristic()
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/schemes/elliptic_curves/isogeny_small_degree.py
> in isogenies_3(E, minimal_models)
> 754 from sage.rings.number_field.number_field_base import
> is_NumberField
> 755 model = "minimal" if minimal_models and
> is_NumberField(E.base_field()) else None
> --> 756 isogs = [E.isogeny(f, model=model) for f in ff]
> 757 return isogs
> 758
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/schemes/elliptic_curves/isogeny_small_degree.py
> in <listcomp>(.0)
> 754 from sage.rings.number_field.number_field_base import
> is_NumberField
> 755 model = "minimal" if minimal_models and
> is_NumberField(E.base_field()) else None
> --> 756 isogs = [E.isogeny(f, model=model) for f in ff]
> 757 return isogs
> 758
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/schemes/elliptic_curves/ell_field.py
> in isogeny(self, kernel, codomain, degree, model, check)
> 876 """
> 877 try:
> --> 878 return EllipticCurveIsogeny(self, kernel, codomain,
> degree, model, check=check)
> 879 except AttributeError as e:
> 880 raise RuntimeError("Unable to construct isogeny: %s" % e)
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/schemes/elliptic_curves/ell_curve_isogeny.py
> in __init__(self, E, kernel, codomain, degree, model, check)
> 1015 self.__compute_E2()
> 1016
> -> 1017 self.__setup_post_isomorphism(codomain, model)
> 1018
> 1019 if (pre_isom is not None):
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/schemes/elliptic_curves/ell_curve_isogeny.py
> in __setup_post_isomorphism(self, codomain, model)
> 1800 raise ValueError("specifying minimal for model
> flag only valid with curves over number fields.")
> 1801
> -> 1802 newE2 = oldE2.global_minimal_model(semi_global=True)
> 1803 post_isom = oldE2.isomorphism_to(newE2)
> 1804
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/schemes/elliptic_curves/ell_number_field.py
> in global_minimal_model(self, proof, semi_global)
> 2042 from .kraus import semi_global_minimal_model
> 2043 E, P = semi_global_minimal_model(self)
> -> 2044 return E._scale_by_units()._reduce_model()
> 2045
> 2046 raise ValueError("%s has no global minimal model! For a
> semi-global minimal model use semi_global=True" % self)
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/schemes/elliptic_curves/ell_number_field.py
> in _scale_by_units(self)
> 987 from sage.modules.all import vector
> 988 v =
> vector([(x4.abs().nth_root(4)+x6.abs().nth_root(6)).log()*d for x4,x6,d in
> zip(c4s,c6s,degs)])
> --> 989 es = [e.round() for e in -Ainv*U*v]
> 990 u = prod([uj**ej for uj,ej in zip(fu,es)])
> 991 return self.scale_curve(u)
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/schemes/elliptic_curves/ell_number_field.py
> in <listcomp>(.0)
> 987 from sage.modules.all import vector
> 988 v =
> vector([(x4.abs().nth_root(4)+x6.abs().nth_root(6)).log()*d for x4,x6,d in
> zip(c4s,c6s,degs)])
> --> 989 es = [e.round() for e in -Ainv*U*v]
> 990 u = prod([uj**ej for uj,ej in zip(fu,es)])
> 991 return self.scale_curve(u)
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/rings/real_mpfr.pyx
> in sage.rings.real_mpfr.RealNumber.round
> (build/cythonized/sage/rings/real_mpfr.c:22391)()
> 3015 cdef RealNumber x = self._new()
> 3016 mpfr_round(x.value, self.value)
> -> 3017 return x.integer_part()
> 3018
> 3019 def floor(self):
>
> /scratch/sage/sage-9.4/local/lib/python3.8/site-packages/sage/rings/real_mpfr.pyx
> in sage.rings.real_mpfr.RealNumber.integer_part
> (build/cythonized/sage/rings/real_mpfr.c:17420)()
> 2256 """
> 2257 if not mpfr_number_p(self.value):
> -> 2258 raise ValueError('Cannot convert infinity or NaN to Sage
> Integer')
> 2259
> 2260 cdef Integer z = Integer()
>
> ValueError: Cannot convert infinity or NaN to Sage Integer
>
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