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:  sage6.8 
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 )
In 5.4, with KASH installed:
NumberField(x^212, 'a').galois_group(type="pari").order()
gives answer 252, but with
NumberField(x^222, '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
comment:2 Changed 6 years ago by
 Description modified (diff)
comment:3 Changed 6 years ago by
 Milestone changed from sage5.11 to sage5.12
comment:4 Changed 6 years ago by
In 5.13beta1 with kash package
NumberField(x^152, 'a').galois_group(type="pari").order()
gives
ValueError: Index n must be in {1,..,None}
comment:5 Changed 6 years ago by
 Milestone changed from sage6.1 to sagewishlist
comment:6 Changed 6 years ago by
 Description modified (diff)
comment:7 Changed 5 years ago by
With sage6.3 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
 Branch set to u/jmantysalo/galois_group_when_polynomial_has_too_high_degree
comment:9 Changed 5 years ago by
 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.tuberlin.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:
cbc8acd  Changed limit of using KASH from <=23 to <=21.

comment:10 Changed 5 years ago by
 Commit changed from cbc8acd14df82c26e5d0d7849cdd7be031f595a0 to f9ab830ba5e62e54df37321b4261b012407fd283
Branch pushed to git repo; I updated commit sha1. New commits:
comment:11 Changed 5 years ago by
 Commit changed from f9ab830ba5e62e54df37321b4261b012407fd283 to a7552058b6da9f37ca71991a2cb7cc79be8bc2b9
Branch pushed to git repo; I updated commit sha1. New commits:
a755205  Changed the limit from 23 to 21.

comment:12 Changed 5 years ago by
 Cc ncohen added
 Milestone changed from sagewishlist to sage6.8
 Priority changed from trivial to minor
 Status changed from new to needs_review
As also the web page http://page.math.tuberlin.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 followup: ↓ 14 Changed 5 years ago by
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
 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
 Reviewers set to Frédéric Chapoton
 Status changed from needs_review to positive_review
comment:16 Changed 5 years ago by
 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
Tested with 5.10: After trying R.<x>=QQ[]; (x^{232).galois_group().order() I can't calculate for example R.<x>=QQ[]; (x}202).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.