Opened 10 years ago

Closed 10 years ago

#13100 closed enhancement (fixed)

EllipticCurve_from_j (over QQ) should not always compute minimal twist

Reported by: John Cremona Owned by: John Cremona
Priority: minor Milestone: sage-5.3
Component: elliptic curves Keywords: elliptic curve construction
Cc: David Roe, Volker Braun Merged in: sage-5.3.beta0
Authors: John Cremona Reviewers: David Roe
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: #13109 Stopgaps:

Status badges

Description (last modified by John Palmieri)

Currently when constructing an elliptic curve from a j-invariant over QQ, a curve with minimal conductor is created (the so-called "minimal twist"). This could be expensive since it involves factoring j and j-1728, so an option to *not* find the minimal twist should be allowed, with the current behaviour as default for backwards compatibility.

For example:

sage: EllipticCurve(j=2^256+1)

currently triggers factorization of F_8 (which is quite quick) but also F_8-1728 (which is not).

Apply trac13100-elliptic-rebased.patch.

Attachments (3)

trac13100-elliptic.patch (7.4 KB) - added by John Cremona 10 years ago.
Applies to 5.1.beta3
trac13100-rebase-on-13109.patch (1.4 KB) - added by John Palmieri 10 years ago.
fix a deprecation
trac13100-elliptic-rebased.patch (7.7 KB) - added by John Palmieri 10 years ago.

Download all attachments as: .zip

Change History (18)

Changed 10 years ago by John Cremona

Attachment: trac13100-elliptic.patch added

Applies to 5.1.beta3

comment:1 Changed 10 years ago by John Cremona

Authors: John Cremona
Cc: David Roe added
Status: newneeds_review

The patch fixes this, and also the issue at #11773 which can be closed as a duplicate.

comment:2 Changed 10 years ago by David Roe

Status: needs_reviewneeds_work

This looks fine to me. I have no idea what the doctest failing on patchbot is about. Patchbot is also complaining about trailing whitespace....

comment:3 in reply to:  2 Changed 10 years ago by John Cremona

Replying to roed:

This looks fine to me. I have no idea what the doctest failing on patchbot is about. Patchbot is also complaining about trailing whitespace....

I removed trailing whitespace on lines I edited (or nearby) but not on the whole file as that makes it harder for reviewers to see what has changed. Of course I could go back and remove the rest. Does patchbot tell us what tests actually fail?

comment:4 Changed 10 years ago by David Roe

Status: needs_workpositive_review

The patchbot will tell you if you click on the yellow disc (or whatever other color it might be), then click on "shortlog."

I ran the tests on my own machine and am not getting the same failure patchbot is. Since I have no idea why your changes would cause a problem in sage.misc.trace, I'm going to give it a positive review.

comment:5 in reply to:  4 Changed 10 years ago by John Cremona

Replying to roed:

The patchbot will tell you if you click on the yellow disc (or whatever other color it might be), then click on "shortlog."

I ran the tests on my own machine and am not getting the same failure patchbot is. Since I have no idea why your changes would cause a problem in sage.misc.trace, I'm going to give it a positive review.

Thanks. I agree that the failure reported by patchbot has nothing to do with this ticket.

comment:6 Changed 10 years ago by Jeroen Demeyer

Milestone: sage-5.1sage-5.2
Reviewers: David Roe

comment:7 Changed 10 years ago by John Palmieri

Cc: Volker Braun added
Dependencies: #13109
Description: modified (diff)
Status: positive_reviewneeds_work

This needs to be rebased to #13109. Patch attached, and I've cc'ed Volker, who should be able to review it quickly.

Changed 10 years ago by John Palmieri

fix a deprecation

comment:8 Changed 10 years ago by John Palmieri

Status: needs_workneeds_review

comment:9 Changed 10 years ago by Volker Braun

John, trac13100-elliptic.patch conflicts with my version of #13109.

comment:10 in reply to:  9 Changed 10 years ago by John Cremona

Replying to vbraun:

John, trac13100-elliptic.patch conflicts with my version of #13109.

I understand, but doesn't Joh Palmieri's patch fix it (thanks John)?

Changed 10 years ago by John Palmieri

comment:11 Changed 10 years ago by John Palmieri

Description: modified (diff)

Sorry, try this one instead. (I got this one confused with another ticket dealing with elliptic curves.)

comment:12 Changed 10 years ago by John Palmieri

Status: needs_reviewpositive_review

This is just a rebasing, so I don't think it needs review.

comment:13 Changed 10 years ago by Jeroen Demeyer

Milestone: sage-5.2sage-pending

comment:14 Changed 10 years ago by Jeroen Demeyer

Milestone: sage-pendingsage-5.3

comment:15 Changed 10 years ago by Jeroen Demeyer

Merged in: sage-5.3.beta0
Resolution: fixed
Status: positive_reviewclosed
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