On Tuesday, August 29, 2017 at 4:29:21 PM UTC-7, Jon Yard wrote: > > > /home/jyard/sage/local/lib/python2.7/site-packages/sage/rings/number_field/galois_group.pyc > > in __init__(self, number_field, names) > > 202 self._number_field = number_field 203 --> 204 if > not number_field.is_galois(): 205 self._galois_closure, > self._gc_map = number_field.galois_closure(names=names, map=True) 206 > else: > /home/jyard/sage/local/lib/python2.7/site-packages/sage/rings/number_field/number_field.pyc > in is_galois(self) 4968 False 4969 """-> 4970 > return self.galois_group(type="pari").order() == self.degree() > > As you can see from the trace-back: this is very sloppy programming. The algorithm for computing the galois group apparently first checks if the field is galois, which computes the galois group to compare its size with the degree. In the process the options get lost.
Reading the code, you'll see the functionality is actually hanging off polynomials, so it'll work better to do this: sage: K=NumberField(x^17-3,name='a') sage: f=K.absolute_polynomial() sage: f.galois_group(algorithm="magma") verbose 0 (2062: permgroup_named.py, cardinality) Warning: TransitiveGroups requires the GAP database package. Please install it with ``sage -i database_gap``. at which point you see that magma's interface is more useful altogether and doesn't get properly interfaced with sage: magma will actually give you the group as a permutation group on the roots (represented in some p-adic extension); no classification of transitive permutation groups required. You'd be welcome to fix this. Personally, after seeing careless code like this, I'd try very hard not to depend on it! If you're going to depend on magma anyway, you might as well stick with it all the way. -- 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 [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/sage-devel. For more options, visit https://groups.google.com/d/optout.
