Is the x you give in these examples the same x as above? I’m worried (maybe
needlessly) about if the x you give includes a summand of kH.one(). If the
x you give does not include a summand of one, then the behavior you
described is consistent with what I think the problem is. If the x in the
new example doesn’t have a summand of kH.one() then I’m misunderstanding
something.
On Sat, Aug 6, 2022 at 6:00 PM keirh...@gmail.com <keirhar...@gmail.com>
wrote:
> Thanks for this workaround. I was passing the group algebra to a function
> and then accessing the base group like so:
>
> kH.group()
>
> Both of the following cause the coercion error:
>
> kH.one() * x
> kH.group().one() * x
>
> But this works fine:
>
> H.one()*x
>
> I will just have to pass the original group along as well.
>
> --Keir
>
> On Saturday, August 6, 2022 at 2:06:51 PM UTC-4 trevor...@gmail.com wrote:
>
>> I can reproduce this on 9.7.beta7.
>>
>> The problem is that the parent is not understood to be the same (even
>> though it clearly is). A workaround is:
>>
>> sage: x = kH(a) + kH(b) + kH(H.one()); x
>>
>> () + (5,6,7)(12,14,18) + (1,2)(3,4)
>>
>> sage: x*x
>>
>> (5,7,6)(12,18,14)
>>
>>
>> Here H.one() puts the one in the right parent for the coercion framework,
>> but this definitely looks like a bug to me, because
>>
>> sage: kH(a).parent()
>>
>> Algebra of Permutation Group with generators [(5,6,7)(12,14,18),
>> (1,2)(3,4)] over Finite Field of size 2
>>
>> sage: kH.one().parent()
>>
>> Algebra of Permutation Group with generators [(5,6,7)(12,14,18),
>> (1,2)(3,4)] over Finite Field of size 2
>>
>> sage: kH(a).parent() is kH.one().parent()
>>
>> True
>>
>>
>> Reproducing the bug with messages on 9.7.beta7:
>>
>> sage: H = PermutationGroup([[(*1*,*2*), (*3*,*4*)], [(*5*,*6*,*7*),(*12*,
>> *14*,*18*)]])
>>
>> sage: kH = H.algebra(GF(*2*))
>>
>> sage: H.gens()
>>
>> ((5,6,7)(12,14,18), (1,2)(3,4))
>>
>> sage: a, b = H.gens()
>>
>> sage: x = kH(a) + kH(b) + kH.one(); x
>>
>> (5,6,7)(12,14,18) + (1,2)(3,4) + ()
>>
>> sage: x*x
>>
>>
>> ---------------------------------------------------------------------------
>>
>> RuntimeError Traceback (most recent call
>> last)
>>
>> Input In [7], in <cell line: 1>()
>>
>> ----> 1 x*x
>>
>>
>> File ~/Applications/sage/src/sage/structure/element.pyx:1514, in
>> sage.structure.element.Element.__mul__()
>>
>> * 1512* cdef int cl = classify_elements(left, right)
>>
>> * 1513* if HAVE_SAME_PARENT(cl):
>>
>> -> 1514 return (<Element>left)._mul_(right)
>>
>> * 1515* if BOTH_ARE_ELEMENT(cl):
>>
>> * 1516* return coercion_model.bin_op(left, right, mul)
>>
>>
>> File ~/Applications/sage/src/sage/structure/element.pyx:1560, in
>> sage.structure.element.Element._mul_()
>>
>> * 1558* raise bin_op_exception('*', self, other)
>>
>> * 1559* else:
>>
>> -> 1560 return python_op(other)
>>
>> * 1561*
>>
>> * 1562* cdef _mul_long(self, long n):
>>
>>
>> File ~/Applications/sage/src/sage/categories/coercion_methods.pyx:53, in
>> sage.categories.coercion_methods._mul_parent()
>>
>> * 51* True
>>
>> * 52* """
>>
>> ---> 53 return (<Element>self)._parent.product(self, other)
>>
>>
>> File ~/Applications/sage/src/sage/categories/magmatic_algebras.py:215, in
>> MagmaticAlgebras.WithBasis.ParentMethods._product_from_product_on_basis_multiply(self,
>> left, right)
>>
>> * 201* *def* _product_from_product_on_basis_multiply( self, left,
>> right ):
>>
>> * 202* r*"""*
>>
>> * 203* * Compute the product of two elements by extending*
>>
>> * 204* * bilinearly the method :meth:`product_on_basis`.*
>>
>> (...)
>>
>> * 213*
>>
>> * 214* * """*
>>
>> --> 215 *return*
>> self.linear_combination((self.product_on_basis(mon_left, mon_right),
>> coeff_left * coeff_right )
>>
>> * 216* *for* (mon_left,
>> coeff_left) *in* left.monomial_coefficients().items()
>>
>> * 217* *for* (mon_right,
>> coeff_right) *in* right.monomial_coefficients().items() )
>>
>>
>> File ~/Applications/sage/src/sage/combinat/free_module.py:969, in
>> CombinatorialFreeModule.linear_combination(self, iter_of_elements_coeff,
>> factor_on_left)
>>
>> * 945* *def* linear_combination(self, iter_of_elements_coeff,
>> factor_on_left=*True*):
>>
>> * 946* r*"""*
>>
>> * 947* * Return the linear combination `\lambda_1 v_1 + \cdots +*
>>
>> * 948* * \lambda_k v_k` (resp. the linear combination `v_1
>> \lambda_1 +*
>>
>> (...)
>>
>> * 967* * 20*B[1] + 20*B[2]*
>>
>> * 968* * """*
>>
>> --> 969 *return*
>> self._from_dict(blas.linear_combination(((element._monomial_coefficients,
>> coeff)
>>
>> * 970* *for*
>> element, coeff *in* iter_of_elements_coeff),
>>
>> * 971*
>> factor_on_left=factor_on_left),
>>
>> * 972* remove_zeros=*False*)
>>
>>
>> File ~/Applications/sage/src/sage/data_structures/blas_dict.pyx:313, in
>> sage.data_structures.blas_dict.linear_combination()
>>
>> * 311* return remove_zeros(result)
>>
>> * 312*
>>
>> --> 313 cpdef dict linear_combination(dict_factor_iter, bint
>> factor_on_left=True):
>>
>> * 314* r"""
>>
>> * 315* Return the pointwise addition of dictionaries with
>> coefficients.
>>
>>
>> File ~/Applications/sage/src/sage/data_structures/blas_dict.pyx:348, in
>> sage.data_structures.blas_dict.linear_combination()
>>
>> * 346* cdef dict D
>>
>> * 347*
>>
>> --> 348 for D, a in dict_factor_iter:
>>
>> * 349* if not a: # We multiply by 0, so nothing to do
>>
>> * 350* continue
>>
>>
>> File ~/Applications/sage/src/sage/combinat/free_module.py:969, in
>> <genexpr>(.0)
>>
>> * 945* *def* linear_combination(self, iter_of_elements_coeff,
>> factor_on_left=*True*):
>>
>> * 946* r*"""*
>>
>> * 947* * Return the linear combination `\lambda_1 v_1 + \cdots +*
>>
>> * 948* * \lambda_k v_k` (resp. the linear combination `v_1
>> \lambda_1 +*
>>
>> (...)
>>
>> * 967* * 20*B[1] + 20*B[2]*
>>
>> * 968* * """*
>>
>> --> 969 *return*
>> self._from_dict(blas.linear_combination(((element._monomial_coefficients,
>> coeff)
>>
>> * 970* *for*
>> element, coeff *in* iter_of_elements_coeff),
>>
>> * 971*
>> factor_on_left=factor_on_left),
>>
>> * 972* remove_zeros=*False*)
>>
>>
>> File ~/Applications/sage/src/sage/categories/magmatic_algebras.py:215, in
>> <genexpr>(.0)
>>
>> * 201* *def* _product_from_product_on_basis_multiply( self, left,
>> right ):
>>
>> * 202* r*"""*
>>
>> * 203* * Compute the product of two elements by extending*
>>
>> * 204* * bilinearly the method :meth:`product_on_basis`.*
>>
>> (...)
>>
>> * 213*
>>
>> * 214* * """*
>>
>> --> 215 *return*
>> self.linear_combination((self.product_on_basis(mon_left, mon_right),
>> coeff_left * coeff_right )
>>
>> * 216* *for* (mon_left,
>> coeff_left) *in* left.monomial_coefficients().items()
>>
>> * 217* *for* (mon_right,
>> coeff_right) *in* right.monomial_coefficients().items() )
>>
>>
>> File ~/Applications/sage/src/sage/categories/semigroups.py:957, in
>> Semigroups.Algebras.ParentMethods.product_on_basis(self, g1, g2)
>>
>> * 939* *def* product_on_basis(self, g1, g2):
>>
>> * 940* r*"""*
>>
>> * 941* * Product, on basis elements, as per*
>>
>> * 942* *
>> :meth:`MagmaticAlgebras.WithBasis.ParentMethods.product_on_basis()*
>>
>> (...)
>>
>> * 955* * B['ab'] + B['bdc']*
>>
>> * 956* * """*
>>
>> --> 957 *return* self.monomial(g1 * g2)
>>
>>
>> File
>> ~/Applications/sage/src/sage/groups/perm_gps/permgroup_element.pyx:1295, in
>> sage.groups.perm_gps.permgroup_element.PermutationGroupElement.__mul__()
>>
>> * 1293* return prod
>>
>> * 1294*
>>
>> -> 1295 return coercion_model.bin_op(left, right, operator.mul)
>>
>> * 1296*
>>
>> * 1297* cpdef _mul_(left, _right):
>>
>>
>> File ~/Applications/sage/src/sage/structure/coerce.pyx:1200, in
>> sage.structure.coerce.CoercionModel.bin_op()
>>
>> * 1198* # Now coerce to a common parent and do the operation there
>>
>> * 1199* try:
>>
>> -> 1200 xy = self.canonical_coercion(x, y)
>>
>> * 1201* except TypeError:
>>
>> * 1202* self._record_exception()
>>
>>
>> File ~/Applications/sage/src/sage/structure/coerce.pyx:1332, in
>> sage.structure.coerce.CoercionModel.canonical_coercion()
>>
>> * 1330* if x_elt._parent is y_elt._parent:
>>
>> * 1331* return x_elt,y_elt
>>
>> -> 1332 self._coercion_error(x, x_map, x_elt, y, y_map, y_elt)
>>
>> * 1333*
>>
>> * 1334* cdef bint x_numeric = isinstance(x, (int, long, float,
>> complex))
>>
>>
>> File ~/Applications/sage/src/sage/structure/coerce.pyx:2031, in
>> sage.structure.coerce.CoercionModel._coercion_error()
>>
>> * 2029* <class 'str'> 'g'
>>
>> * 2030* """
>>
>> -> 2031 raise RuntimeError("""There is a bug in the coercion code
>> in Sage.
>>
>> * 2032* Both x (=%r) and y (=%r) are supposed to have identical
>> parents but they don't.
>>
>> * 2033* In fact, x has parent '%s'
>>
>>
>> RuntimeError: There is a bug in the coercion code in Sage.
>>
>> Both x (=()) and y (=(5,6,7)(12,14,18)) are supposed to have identical
>> parents but they don't.
>>
>> In fact, x has parent 'Permutation Group with generators
>> [(5,6,7)(12,14,18), (1,2)(3,4)]'
>>
>> whereas y has parent 'Permutation Group with generators
>> [(5,6,7)(12,14,18), (1,2)(3,4)]'
>>
>> Original elements () (parent Permutation Group with generators
>> [(5,6,7)(12,14,18), (1,2)(3,4)]) and (5,6,7)(12,14,18) (parent Permutation
>> Group with generators [(5,6,7)(12,14,18), (1,2)(3,4)]) and maps
>>
>> <class 'NoneType'> None
>>
>> <class 'sage.structure.coerce_maps.DefaultConvertMap_unique'> (map
>> internal to coercion system -- copy before use)
>>
>> Coercion map:
>>
>> From: Permutation Group with generators [(5,6,7)(12,14,18), (1,2)(3,4)]
>>
>> To: Permutation Group with generators [(5,6,7)(12,14,18), (1,2)(3,4)]
>> On Friday, August 5, 2022 at 4:21:09 PM UTC-7 keirh...@gmail.com wrote:
>>
>>> The Sage version I was using is 9.6.
>>>
>>> On Friday, August 5, 2022 at 7:19:48 PM UTC-4 keirh...@gmail.com wrote:
>>>
>>>> When I do this:
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> *H = PermutationGroup([ [(1,2), (3,4)], [(5,6,7),(12,14,18)] ])kH =
>>>> H.algebra(GF(2))[a, b] = H.gens()x = kH(a) + kH(b) + kH.one(); print(x)x*x*
>>>>
>>>> I get an error caused by the last computation: "RuntimeError: There is
>>>> a bug in the coercion code in Sage." (I was working in Cocalc, but you can
>>>> cut and paste the code above into a SageMathCell and reproduce the error.)
>>>>
>>>> Is this really a bug, or should I be doing this differently? (I found
>>>> the problem working with a larger group, but this simpler example above has
>>>> the same issue.)
>>>>
>>>> Thanks --
>>>>
>>>> Keir
>>>>
>>> --
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--
Best,
Trevor
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