Hi folks,
Gamma_H(N) are SL_2(Z) matrices where the lower left entry is
congruent to 0 mod N, and the upper left and lower right entries are
elements of a specified subgroup H of (Z/N)^*.
Sage raises an exception when computing ModularSymbols for the congruence
subgroup Gamma_H(N) of weight 2. Is this a bug?
Regards,
Ifti
===
sage: G = GammaH(36, [13,19])
sage: MS = ModularSymbols(G)
---------------------------------------------------------------------------
<type 'exceptions.AssertionError'> Traceback (most recent call
last)
/home/burhanud/<ipython console> in <module>()
/home/was/s/local/lib/python2.5/site-packages/sage/modular/modsym/modsym.py
in ModularSymbols(group, weight, sign, base_ring, use_cache)
226 elif congroup.is_GammaH(group):
227
--> 228 M = ambient.ModularSymbolsAmbient_wtk_gamma_h(group,
weight, sign, base_ring)
229
230 elif isinstance(group, tuple):
/home/was/s/local/lib/python2.5/site-packages/sage/modular/modsym/ambient.py
in __init__(self, group, weight, sign, F)
1756 ModularSymbolsAmbient.__init__(self,
1757 weight=weight, group=group,
-> 1758 sign=sign, base_ring=F)
1759
1760 def _dimension_formula(self):
/home/was/s/local/lib/python2.5/site-packages/sage/modular/modsym/ambient.py
in __init__(self, group, weight, sign, base_ring, character)
116 except NotImplementedError:
117 formula = None
--> 118 rank = self.rank()
119 if formula != None:
120 assert rank == formula, \
/home/was/s/local/lib/python2.5/site-packages/sage/modular/modsym/ambient.py
in rank(self)
850 return self.__rank
851 except AttributeError:
--> 852 self.__rank = len(self.manin_basis())
853 return self.__rank
854
/home/was/s/local/lib/python2.5/site-packages/sage/modular/modsym/ambient.py
in manin_basis(self)
179 return self._manin_basis
180 except AttributeError:
--> 181 self.compute_presentation()
182 return self._manin_basis
183
/home/was/s/local/lib/python2.5/site-packages/sage/modular/modsym/ambient.py
in compute_presentation(self)
195 B, basis, mod = relation_matrix.compute_presentation(
196 self.manin_symbols(), self.sign(),
--> 197 self.base_ring(), self.weight())
198 self._manin_generators =
self.manin_symbols().manin_symbol_list()
199 self._manin_basis = basis
/home/was/s/local/lib/python2.5/site-packages/sage/modular/modsym/relation_matrix.py
in compute_presentation(syms, sign, field, weight, sparse)
329 else:
330 sparse = True
--> 331 R, mod = relation_matrix_wtk_g0(syms, sign, field, weight,
sparse)
332 B, basis = gens_to_basis_matrix(syms, R, mod, field, sparse)
333 return B, basis, mod
/home/was/s/local/lib/python2.5/site-packages/sage/modular/modsym/relation_matrix.py
in relation_matrix_wtk_g0(syms, sign, field, weight, sparse)
334
335 def relation_matrix_wtk_g0(syms, sign, field, weight, sparse):
--> 336 rels = modS_relations(syms)
337 if sign != 0:
338 # Let rels = rels union I relations.
/home/was/s/local/lib/python2.5/site-packages/sage/modular/modsym/relation_matrix.py
in modS_relations(syms)
99 for i in xrange(len(syms)):
100 j, s = syms.apply_S(i)
--> 101 assert j != -1
102 if i < j:
103 rels.add( ((i,1),(j,s)) )
<type 'exceptions.AssertionError'>:
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