btquotient ValueError: negative valuation

[Eloitor]

Steps To Reproduce

sage: X = BruhatTitsQuotient(7, 5*17*13)
sage: X
Quotient of the Bruhat Tits tree of GL_2(QQ_7) with discriminant 5 * 13 * 17 and level 1
sage: X.get_maximal_order()
Order of Quaternion Algebra (-7, -1105) with base ring Rational Field with basis (1, 1/2 + 1/2*i, j, 1/2 + 1/14*i + 1/2*j + 1/14*k)
sage: X.plot()

Expected Behavior

A plot of the graph of the btquotient is shown.

Actual Behavior

I get the following ValueError:

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/modular/btquotients/btquotient.py:2040, in BruhatTitsQuotient.get_graph(self)
   2039 try:
-> 2040     return self._S
   2041 except AttributeError:

AttributeError: 'BruhatTitsQuotient' object has no attribute '_S'

During handling of the above exception, another exception occurred:

ValueError                                Traceback (most recent call last)
Cell In[3], line 1
----> 1 X.plot()

File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/modular/btquotients/btquotient.py:2075, in BruhatTitsQuotient.plot(self, *args, **kwargs)
   2063 def plot(self, *args, **kwargs):
   2064     r"""
   2065     Plot the quotient graph.
   2066
   (...)   2073         Graphics object consisting of 17 graphics primitives
   2074     """
-> 2075     S = self.get_graph()
   2076     vertex_colors = {}
   2077     v0 = Matrix(ZZ, 2, 2, [1, 0, 0, 1])

File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/modular/btquotients/btquotient.py:2042, in BruhatTitsQuotient.get_graph(self)
   2040     return self._S
   2041 except AttributeError:
-> 2042     self._compute_quotient()
   2043     return self._S

File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/modular/btquotients/btquotient.py:3533, in BruhatTitsQuotient._compute_quotient(self, check)
   3531 num_verts = 0
   3532 num_edges = 0
-> 3533 self.get_embedding_matrix(prec=3)
   3534 p = self._p
   3535 v0 = Vertex(p, num_verts, self._Mat_22([1, 0, 0, 1]),
   3536             determinant=1, valuation=0)

File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/modular/btquotients/btquotient.py:2442, in BruhatTitsQuotient.get_embedding_matrix(self, prec, exact)
   2440 if prec > self._prec:
   2441     verbose('self._prec = %s, prec = %s' % (self._prec, prec))
-> 2442     Iotamod = self._compute_embedding_matrix(prec)
   2443     self._Iotainv_lift = Iotamod.inverse().lift()
   2444     self._Iota = Matrix(self._R, 4, 4, [Iotamod[ii, jj]
   2445                                         for ii in range(4)
   2446                                         for jj in range(4)])

File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/modular/btquotients/btquotient.py:2277, in BruhatTitsQuotient._compute_embedding_matrix(self, prec, force_computation)
   2274 phi = self._local_splitting_map(prec)
   2275 B = self.get_eichler_order_basis()
   2276 return Matrix(Zmod(self._p ** prec), 4, 4,
-> 2277               [phi(B[kk])[ii, jj] for ii in range(2)
   2278                for jj in range(2) for kk in range(4)])

File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/modular/btquotients/btquotient.py:2176, in BruhatTitsQuotient._local_splitting_map.<locals>.phi(q)
   2174 R = I.parent()
   2175 v = q.coefficient_tuple()
-> 2176 return R(v[0] + I * v[1] + J * v[2] + K * v[3])

File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/structure/parent.pyx:900, in sage.structure.parent.Parent.__call__ (build/cythonized/sage/structure/parent.c:12762)()
    898 if mor is not None:
    899     if no_extra_args:
--> 900         return mor._call_(x)
    901     else:
    902         return mor._call_with_args(x, args, kwds)

File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/structure/coerce_maps.pyx:164, in sage.structure.coerce_maps.DefaultConvertMap_unique._call_ (build/cythonized/sage/structure/coerce_maps.c:6979)()
    162             print(type(C), C)
    163             print(type(C._element_constructor), C._element_constructor)
--> 164         raise
    165
    166 cpdef Element _call_with_args(self, x, args=(), kwds={}):

File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/structure/coerce_maps.pyx:159, in sage.structure.coerce_maps.DefaultConvertMap_unique._call_ (build/cythonized/sage/structure/coerce_maps.c:6871)()
    157 cdef Parent C = self._codomain
    158 try:
--> 159     return C._element_constructor(x)
    160 except Exception:
    161     if print_warnings:

File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/matrix/matrix_space.py:1172, in MatrixSpace._element_constructor_(self, entries, **kwds)
   1054 def _element_constructor_(self, entries, **kwds):
   1055     """
   1056     Construct an element of ``self`` from ``entries``.
   1057
   (...)   1170         False
   1171     """
-> 1172     return self.element_class(self, entries, **kwds)

File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/matrix/matrix_generic_dense.pyx:82, in sage.matrix.matrix_generic_dense.Matrix_generic_dense.__init__ (build/cythonized/sage/matrix/matrix_generic_dense.c:5911)()
     80     """
     81     ma = MatrixArgs_init(parent, entries)
---> 82     self._entries = ma.list(coerce)
     83
     84 cdef Matrix_generic_dense _new(self, Py_ssize_t nrows, Py_ssize_t ncols):

File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/matrix/args.pyx:872, in sage.matrix.args.MatrixArgs.list (build/cythonized/sage/matrix/args.c:15065)()
    870             L = L[:]
    871 else:
--> 872     L = list(self.iter(convert))
    873
    874 cdef long N = self.nrows * self.ncols

File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/matrix/args.pyx:651, in iter (build/cythonized/sage/matrix/args.c:13569)()
    649 x = m[i, j]
    650 if convert and self.need_to_convert(x):
--> 651     x = self.base(x)
    652 if sparse:
    653     yield make_SparseEntry(i, j, x)

File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/structure/parent.pyx:900, in sage.structure.parent.Parent.__call__ (build/cythonized/sage/structure/parent.c:12762)()
    898 if mor is not None:
    899     if no_extra_args:
--> 900         return mor._call_(x)
    901     else:
    902         return mor._call_with_args(x, args, kwds)

File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/structure/coerce_maps.pyx:164, in sage.structure.coerce_maps.DefaultConvertMap_unique._call_ (build/cythonized/sage/structure/coerce_maps.c:6979)()
    162             print(type(C), C)
    163             print(type(C._element_constructor), C._element_constructor)
--> 164         raise
    165
    166 cpdef Element _call_with_args(self, x, args=(), kwds={}):

File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/structure/coerce_maps.pyx:159, in sage.structure.coerce_maps.DefaultConvertMap_unique._call_ (build/cythonized/sage/structure/coerce_maps.c:6871)()
    157 cdef Parent C = self._codomain
    158 try:
--> 159     return C._element_constructor(x)
    160 except Exception:
    161     if print_warnings:

File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/categories/sets_cat.py:1011, in Sets.ParentMethods._element_constructor_from_element_class(self, *args, **keywords)
    991 def _element_constructor_from_element_class(self, *args, **keywords):
    992     """
    993     The default constructor for elements of this parent ``self``.
    994
   (...)   1009         <class 'sage.categories.examples.sets_cat.PrimeNumbers_Inherits_with_category.element_class'>
   1010     """
-> 1011     return self.element_class(self, *args, **keywords)

File /private/var/tmp/sage-10.6-current/local/var/lib/sage/venv-python3.12.5/lib/python3.12/site-packages/sage/rings/padics/padic_template_element.pxi:166, in sage.rings.padics.padic_capped_relative_element.pAdicTemplateElement.__init__ (build/cythonized/sage/rings/padics/padic_capped_relative_element.c:14337)()
    164 val = get_ordp(x, self.prime_pow)
    165 if val < 0 and self.prime_pow.in_field == 0:
--> 166     raise ValueError("negative valuation")
    167 xprec = get_preccap(x, self.prime_pow)
    168 self._set(x, val, xprec, absprec, relprec)

ValueError: negative valuation

Additional Information

The issue is caused because 7 is in the denominator of the basis of the maximal order.

Environment

• OS: MacOS 15.5
• Sage Version: 10.6

Checklist

• I have searched the existing issues for a bug report that matches the one I want to file, without success.
• I have read the documentation and troubleshoot guide

[Eloitor]

With a magma installation it works:

sage: X = BruhatTitsQuotient(7, 5*17*13, use_magma=True,  magma_session=magma)
sage: X.plot()
Launched png viewer for Graphics object consisting of 513 graphics primitives

I think the error is in

sage/src/sage/modular/btquotients/btquotient.py

Line 2179 in 9352a32

def _local_splitting(self, prec):

, which doesn't take the maximal order into account, and therefore the image of the basis of the maximal order might have negative p-adic valuation.