elliptic curves -- heegner_index command gives nonsense when rank > 1

[williamstein]

For any elliptic curve over QQ of rank >= 2 the heegner_index command must always give +Infinity as output. So the following 1 at the end is just wrong.

sage: E = EllipticCurve('389a')
sage: D = E.heegner_discriminants_list(1)[0]
sage: D
-7
sage: E.heegner_index(D)
1

Apply trac_4453-rebased.patch and 4453-doctest-fix.patch

Component: elliptic curves

Author: William Stein

Reviewer: John Cremona, Robert Bradshaw

Merged: sage-5.5.beta1

Issue created by migration from https://trac.sagemath.org/ticket/4453

[robertwb]

comment:4

Depends on #6616?

[JohnCremona]

Author: was

[JohnCremona]

Reviewer: cremona

[JohnCremona]

comment:5

Positive review: looks good (apart from a docstring typo "We higher rank examples") and applies fine to 4.3.1, tests pass and docs build & look good.

I added a new patch which changes the above to "Some higher rank examples" with no further changes.

[sagetrac-mvngu]

comment:6

I get two hunk failures when applying trac_4453.2.patch on top of Sage 4.3.3.alpha0:

[mvngu@sage sage-main]$ pwd
/dev/shm/mvngu/sage-4.3.3.alpha0/devel/sage-main
[mvngu@sage sage-main]$ hg qimport https://github.com/sagemath/sage/files/ticket4453/trac_4453.2.patch.gz && hg qpush
adding trac_4453.2.patch to series file
applying trac_4453.2.patch
patching file sage/schemes/elliptic_curves/heegner.py
Hunk #3 FAILED at 6350
Hunk #4 succeeded at 6370 with fuzz 2 (offset -12 lines).
Hunk #5 FAILED at 6430
2 out of 5 hunks FAILED -- saving rejects to file sage/schemes/elliptic_curves/heegner.py.rej
patch failed, unable to continue (try -v)
patch failed, rejects left in working dir
errors during apply, please fix and refresh trac_4453.2.patch

The attachment trac_4453.2.patch needs rebase against Sage 4.3.3.alpha0.

[sagetrac-mvngu]

Work Issues: rebase against Sage 4.3.3.alpha0

[robertwb]

Attachment: trac_4453-rebased.patch.gz

[robertwb]

comment:7

Rebased, I also fixed a small error when check_rank=False.

[qed777]

Changed reviewer from cremona to John Cremona

[qed777]

Changed author from was to William Stein

[qed777]

Changed work issues from rebase against Sage 4.3.3.alpha0 to none

[qed777]

comment:8

With the forthcoming 4.5.2 (4.5.2.rc0 + #9226) and the rebased patch, I get a doctest failure:

sage -t -long "devel/sage/sage/schemes/elliptic_curves/heegner.py"
**********************************************************************
File "/mnt/usb1/scratch/mpatel/apps/sage-4.5.2/devel/sage/sage/schemes/elliptic_curves/heegner.py", line 6465:
    sage: E.heegner_index(-8, descent_second_limit=16)
Exception raised:
    Traceback (most recent call last):
      File "/mnt/usb1/scratch/mpatel/apps/sage-4.5.2/local/bin/ncadoctest.py", line 1231, in run_one_test
        self.run_one_example(test, example, filename, compileflags)
      File "/mnt/usb1/scratch/mpatel/apps/sage-4.5.2/local/bin/sagedoctest.py", line 38, in run_one_example
        OrigDocTestRunner.run_one_example(self, test, example, filename, compileflags)
      File "/mnt/usb1/scratch/mpatel/apps/sage-4.5.2/local/bin/ncadoctest.py", line 1172, in run_one_example
        compileflags, 1) in test.globs
      File "<doctest __main__.example_229[14]>", line 1, in <module>
        E.heegner_index(-Integer(8), descent_second_limit=Integer(16))###line 6465: 
    sage: E.heegner_index(-8, descent_second_limit=16)
      File "/mnt/usb1/scratch/mpatel/apps/sage-4.5.2/local/lib/python/site-packages/sage/schemes/elliptic_curves/heegner.py", line 6485, in heegner_index
        if check_rank and self.rank() >= 2:
      File "/mnt/usb1/scratch/mpatel/apps/sage-4.5.2/local/lib/python/site-packages/sage/schemes/elliptic_curves/ell_rational_field.py", line 1741, in rank
        raise RuntimeError, 'Rank not provably correct.'
    RuntimeError: Rank not provably correct.
**********************************************************************
1 items had failures:
   1 of  21 in __main__.example_229
***Test Failed*** 1 failures.

[robertwb]

comment:14

Attachment: 4453-doctest-fix.patch.gz

Apply trac_4453-rebased.patch, 4453-doctest-fix.patch

[robertwb]

Changed reviewer from John Cremona to John Cremona, Robert Bradshaw

[robertwb]

Changed work issues from one doctest fails to none

[zimmermann6]

comment:16

Robert, I find it strange that you give a positive review to your own patch...

Paul

[robertwb]

comment:17

I was giving a positive review to the original patch; I suppose someone should review my 1-line doctest fix as well.

[JohnCremona]

comment:19

I'll check Robert's one-liner but not this week.

[loefflerd]

comment:20

Rob's patch looks fine to me, and patchbot's happy with it, so let's get this in.

[jdemeyer]

comment:22

Please specify which patch(es) to apply.

[jdemeyer]

Merged: sage-5.5.beta1