Opened 10 years ago

Closed 9 years ago

#11372 closed defect (fixed)

nasty side effect of a failed simon_two_descent search

Reported by: was Owned by: cremona
Priority: critical Milestone: sage-5.0
Component: elliptic curves Keywords: rd2
Cc: Merged in: sage-5.0.beta11
Authors: William Stein Reviewers: Jennifer Balakrishnan
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: Stopgaps:

Description (last modified by jdemeyer)

This could seriously confuse a person:

deep:sage-4.7.rc1 wstein$ ./sage
----------------------------------------------------------------------
| Sage Version 4.7.rc1, Release Date: 2011-04-29                     |
| Type notebook() for the GUI, and license() for information.        |
----------------------------------------------------------------------
sage: E = EllipticCurve([1, 1, 0, -23611790086, 1396491910863060])
sage: E.simon_two_descent()
(1, 2, [(88716 : -44358 : 1)])
sage: E.gens()
[]
sage: E.rank()
0
sage: E = EllipticCurve([1, 1, 0, -23611790086, 1396491910863060])
sage: E.gens()
[(4311692542083/48594841 : -13035144436525227/338754636611 : 1)]

The point that simon_two_descent finds is a torsion point. But for some reason E then thinks it has rank 0! Even though simon_two_descent's first output was 1, and in fact E has rank 1. This is pretty scary.

Related: #11005 (Update Simon's GP scripts and convert to use via gp2c)

Attachments (1)

trac_11372.patch (1.8 KB) - added by was 9 years ago.

Download all attachments as: .zip

Change History (9)

comment:1 Changed 10 years ago by jdemeyer

  • Description modified (diff)

comment:2 Changed 10 years ago by was

This may be a dup, because Cremona says: "Yet another one of many related bugs being looked at and/or already fixed, see #10832 and #11005 and #11130 and ...."

comment:3 Changed 9 years ago by jen

  • Stopgaps set to #12695

Changed 9 years ago by was

comment:4 Changed 9 years ago by was

  • Status changed from new to needs_review

comment:5 Changed 9 years ago by was

  • Reviewers set to Jennifer Balakrishnan

comment:6 Changed 9 years ago by jen

  • Keywords rd2 added
  • Status changed from needs_review to positive_review
  • Stopgaps #12695 deleted

Looks great, and all tests pass. 

Could someone else go to the stopgap ticket (#12695) and mark that it's no longer needed?

comment:7 Changed 9 years ago by jdemeyer

  • Authors set to William Stein

comment:8 Changed 9 years ago by jdemeyer

  • Merged in set to sage-5.0.beta11
  • Resolution set to fixed
  • Status changed from positive_review to closed
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