Opened 7 years ago

Closed 5 years ago

#13810 closed defect (fixed)

Galois group when polynomial has too high degree

Reported by: jmantysalo Owned by: davidloeffler
Priority: minor Milestone: sage-6.8
Component: number fields Keywords:
Cc: Merged in:
Authors: Jori Mäntysalo Reviewers: Frédéric Chapoton
Report Upstream: N/A Work issues:
Branch: a755205 (Commits) Commit: a7552058b6da9f37ca71991a2cb7cc79be8bc2b9
Dependencies: Stopgaps:

Description (last modified by jdemeyer)

In 5.4, with KASH installed:

NumberField(x^21-2, 'a').galois_group(type="pari").order()

gives answer 252, but with

NumberField(x^22-2, 'a').galois_group(type="pari").order()

I got

Error, the variable '_s_' must have a value

I guess this relates to kash interface.

Change History (16)

comment:1 Changed 6 years ago by jmantysalo

Tested with 5.10: After trying R.<x>=QQ[]; (x23-2).galois_group().order() I can't calculate for example R.<x>=QQ[]; (x20-2).galois_group().order(). It seems that internal(?) kash instance fails and Sage don't notice it. User must restart worksheet to get this running again.

comment:2 Changed 6 years ago by chapoton

  • Description modified (diff)

comment:3 Changed 6 years ago by jdemeyer

  • Milestone changed from sage-5.11 to sage-5.12

comment:4 Changed 6 years ago by jmantysalo

In 5.13beta1 with kash package

NumberField(x^15-2, 'a').galois_group(type="pari").order()

gives

ValueError: Index n must be in {1,..,None}

comment:5 Changed 6 years ago by jdemeyer

  • Milestone changed from sage-6.1 to sage-wishlist

comment:6 Changed 6 years ago by jdemeyer

  • Description modified (diff)

comment:7 Changed 5 years ago by jmantysalo

With sage-6.3 this is slightly more buggy: Trying to with 23. degreee polynomial sage says "Kash crashed -- automatically restarting." but system does not restart kash.

comment:8 Changed 5 years ago by jmantysalo

  • Branch set to u/jmantysalo/galois_group_when_polynomial_has_too_high_degree

comment:9 Changed 5 years ago by jmantysalo

  • Commit set to cbc8acd14df82c26e5d0d7849cdd7be031f595a0

There has been some other modifications on src/sage/rings/polynomial/polynomial_rational_flint.pyx that conflicts with this patch.

In any case, http://page.math.tu-berlin.de/~kant/.3a6ca5.html clearly says that polynomials up to degree 23 are supported. But just changing given example x_O:=MaximalOrder(X^2+5); Galois(x_O); to have x^23+5 gives segfault and degree 22 get stuck. So I suggests trying KASH only when degree <= 21.


New commits:

cbc8acdChanged limit of using KASH from <=23 to <=21.

comment:10 Changed 5 years ago by git

  • Commit changed from cbc8acd14df82c26e5d0d7849cdd7be031f595a0 to f9ab830ba5e62e54df37321b4261b012407fd283

Branch pushed to git repo; I updated commit sha1. New commits:

comment:11 Changed 5 years ago by git

  • Commit changed from f9ab830ba5e62e54df37321b4261b012407fd283 to a7552058b6da9f37ca71991a2cb7cc79be8bc2b9

Branch pushed to git repo; I updated commit sha1. New commits:

a755205Changed the limit from 23 to 21.

comment:12 Changed 5 years ago by jmantysalo

  • Authors set to Jori Mäntysalo
  • Cc ncohen added
  • Milestone changed from sage-wishlist to sage-6.8
  • Priority changed from trivial to minor
  • Status changed from new to needs_review

As also the web page http://page.math.tu-berlin.de/~kant/kash.html has been changed to "polynomials over Q up to degree 21" (from 23), I think this is clearly the right thing to do.

comment:13 follow-up: Changed 5 years ago by ncohen

I am getting tired of your adding me in Cc of your ticket every single time you want a review.

Nathann

comment:14 in reply to: ↑ 13 Changed 5 years ago by jmantysalo

  • Cc ncohen removed

Replying to ncohen:

I am getting tired of your adding me in Cc of your ticket every single time you want a review.

OK, I'll stop doing that. Sorry.

comment:15 Changed 5 years ago by chapoton

  • Reviewers set to Frédéric Chapoton
  • Status changed from needs_review to positive_review

comment:16 Changed 5 years ago by vbraun

  • Branch changed from u/jmantysalo/galois_group_when_polynomial_has_too_high_degree to a7552058b6da9f37ca71991a2cb7cc79be8bc2b9
  • Resolution set to fixed
  • Status changed from positive_review to closed
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