Debian Bug report logs - #709073
Some computations give errors

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Package: genus2reduction; Maintainer for genus2reduction is Tim Abbott <tabbott@mit.edu>; Source for genus2reduction is src:genus2reduction.

Reported by: Julien Puydt <julien.puydt@laposte.net>

Date: Mon, 20 May 2013 15:27:06 UTC

Severity: normal

Found in version genus2reduction/0.3-2.2

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Report forwarded to debian-bugs-dist@lists.debian.org, Tim Abbott <tabbott@mit.edu>:
Bug#709073; Package genus2reduction. (Mon, 20 May 2013 15:27:10 GMT) Full text and rfc822 format available.

Acknowledgement sent to Julien Puydt <julien.puydt@laposte.net>:
New Bug report received and forwarded. Copy sent to Tim Abbott <tabbott@mit.edu>. (Mon, 20 May 2013 15:27:10 GMT) Full text and rfc822 format available.

Message #5 received at submit@bugs.debian.org (full text, mbox):

From: Julien Puydt <julien.puydt@laposte.net>
To: Debian Bug Tracking System <submit@bugs.debian.org>
Subject: Some computations give errors
Date: Mon, 20 May 2013 17:24:27 +0200
Package: genus2reduction
Version: 0.3-2.2

Here is a computation with debian's package:
$ genus2reduction

enter Q(x) : x^3+x^2+x
enter P(x) : -2*x^5+3*x^4-x^3-x^2-6*x-2

factorization CPU time = 20
a minimal equation over Z[1/2] is :
y^2 = x^6+18*x^3+36*x^2-27

factorization of the minimal (away from 2) discriminant :
[2,1;3,15;53,1]

p=2
(potential) stable reduction :  (II), j=1
reduction at p : [I{1-0-0}] page 170, (1), f=1
p=3
(potential) stable reduction :  (I)
reduction at p :   ***   at top-level: mod(y,y^2-3)
  ***                 ^------------
  ***   not a function in function call
  ***   Error in the PARI system. End of program.

and with sage's package:
$ genus2reduction

enter Q(x) : x^3+x^2+x
enter P(x) : -2*x^5+3*x^4-x^3-x^2-6*x-2

factorization CPU time = 8
a minimal equation over Z[1/2] is :
y^2 = x^6+18*x^3+36*x^2-27

factorization of the minimal (away from 2) discriminant :
[2,1;3,15;53,1]

p=2
(potential) stable reduction :  (II), j=1
reduction at p : [I{1-0-0}] page 170, (1), f=1
p=3
(potential) stable reduction :  (I)
reduction at p : [II] page 155, (1), f=2
p=53
(potential) stable reduction :  (II), j=12
reduction at p : [I{1-0-0}] page 170, (1), f=1

the conductor is 954
in factorized form : [2,1;3,2;53,1]
total CPU time = 12


So there's something wrong going on, not sure what.

Snark on #debian-science



Information forwarded to debian-bugs-dist@lists.debian.org, Tim Abbott <tabbott@mit.edu>:
Bug#709073; Package genus2reduction. (Sun, 15 Sep 2013 21:09:04 GMT) Full text and rfc822 format available.

Acknowledgement sent to Tobias Hansen <thansen@debian.org>:
Extra info received and forwarded to list. Copy sent to Tim Abbott <tabbott@mit.edu>. (Sun, 15 Sep 2013 21:09:04 GMT) Full text and rfc822 format available.

Message #10 received at 709073@bugs.debian.org (full text, mbox):

From: Tobias Hansen <thansen@debian.org>
To: 709073@bugs.debian.org, Julien Puydt <julien.puydt@laposte.net>
Subject: Re: genus2reduction: Some computations give errors
Date: Sun, 15 Sep 2013 22:39:45 +0200
Hi Julien, hi bug,

although it looks like we have the same program as Sage because we both
have version 0.3 and Sage doesn't have patches, the program in Sage is
actually quite different. They just edit the sources directly. Ours does
not even build anymore against new Pari versions. Anyway,
genus2reduction was included into Pari 2.6.1 [1], so once that is
included in Sage, the package is hopefully not needed anymore. We could
either take the new g2r from Sage or just wait for them to change to a
new Pari.

Cheers,
Tobias

[1] http://www.math.u-bordeaux1.fr/~qliu/G2R/



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