Changes between Version 7 and Version 9 of Ticket #10745


Ignore:
Timestamp:
02/12/14 15:59:12 (8 years ago)
Author:
pbruin
Comment:

Given that the documentation no longer says that the points returned by gens() are linearly independent or span a subgroup of full rank, this is technically not a bug anymore, but there is still the inconsistency with the similar function over Q. There seem to be three options:

  1. close this ticket as invalid or wontfix;
  2. use this ticket to print a warning or raise an error if gens() returns something other than a basis for a subgroup of full rank in the Mordell-Weil group;
  3. rewrite this ticket with a more ambitious goal as in comment:6.

Any ideas?

Legend:

Unmodified
Added
Removed
Modified
  • Ticket #10745

    • Property Status changed from new to needs_info
  • Ticket #10745 – Description

    v7 v9  
    1111[]
    1212}}}
     13This isn't very good, because the default in Sage is proof=True, so one would expect this to be a provable result (until reading the docs of course).
    1314
    14 This isn't very good, because the default in Sage is proof=True, so one would expect this to be a provable result (until reading the docs of course. But if we try to look harder for the point, we run into a bug with caching:
     15Over Q, if the result is not provable an error is raised or a warning is printed, depending on the `proof` flag. This should be the same here.
    1516
     17In earlier versions of Sage (< 6.0), there was also a bug with caching:
    1618{{{
    1719sage: FK.gens(lim1=6)
    18 ---------------------------------------------------------------------------
    19 KeyError                                  Traceback (most recent call last)
    20 
    21 /home/rlmill/<ipython console> in <module>()
    22 
    23 /home/rlmill/sage-4.6.2.alpha2/local/lib/python2.6/site-packages/sage/schemes/elliptic_curves/ell_number_field.pyc in gens(self, verbose, lim1, lim3, limtriv, maxprob, limbigprime)
    24    1772         """
    25    1773
    26 -> 1774         lower,upper,gens = self.simon_two_descent(verbose=verbose,lim1=lim1,lim3=lim3,limtriv=limtriv,maxprob=maxprob,limbigprime=limbigprime)
    27    1775         return gens
    28    1776
    29 
    30 /home/rlmill/sage-4.6.2.alpha2/local/lib/python2.6/site-packages/sage/schemes/elliptic_curves/ell_number_field.pyc in simon_two_descent(self, verbose, lim1, lim3, limtriv, maxprob, limbigprime)
    31     265         
    32     266         try:
    33 --> 267             result = self._simon_two_descent_data[lim1,lim3,limtriv,maxprob,limbigprime]
    34     268             if verbose == 0:
    35     269                 return result
    36 
     20Traceback (most recent call last):
     21...
    3722KeyError: (6, 50, 10, 20, 30)
    3823}}}
    39 
    40 So two problems: 1) Over Q, if the result is not provable a RuntimeError is raised. This should be the same here. 2) One can't change parameters due to the way the output is being cached.