#5204: [with new patch, positive review] simon_two_descent -- bug in the
interface
when number field has variable name 'x'
---------------------------+------------------------------------------------
Reporter: was | Owner: was
Type: defect | Status: new
Priority: major | Milestone: sage-3.4.2
Component: number theory | Keywords:
---------------------------+------------------------------------------------
Comment(by cremona):
The following example actually came up today:
{{{
sage: K.<b>=QuadraticField(43)
sage: E=EllipticCurve([0,0,0,0,(-3697884*b - 24248647)])
sage: E.simon_two_descent()
NameError Traceback (most recent call
last)
...
NameError: name 'ans' is not defined
}}}
This is after the patches are applied, so bad news. I called the field
generator 'b' since earlier I had called it 'a' and thought that might be
the problem.
It turns out that it is a bug in simon's ell.gp:
{{{
GP/PARI CALCULATOR Version 2.3.3 (released)
i686 running linux (ix86/GMP-4.2.1 kernel) 32-bit version
compiled: Mar 12 2009, gcc-4.1.2 20070115 (SUSE Linux)
(readline v5.2 enabled, extended help available)
Copyright (C) 2000-2006 The PARI Group
PARI/GP is free software, covered by the GNU General Public
License, and comes WITHOUT ANY WARRANTY WHATSOEVER.
Type ? for help, \q to quit.
Type ?12 for how to get moral (and possibly technical) support.
parisize = 4000000, primelimit = 500000
? \r ell.gp
? K = bnfinit(y^2 - 43);
? a = Mod(y,K.pol);
? bnfellrank(K, [0,0,0,0,-3697884*a - 24248647]);
courbe elliptique : Y^2 = x^3 + Mod(-3697884*y - 24248647, y^2 - 43)
points triviaux sur la courbe = [[1, 1, 0]]
*** array index (1) out of allowed range [none]:
*** ...iv,r=nfsqrt(nf,norm(zc))[1];if(DEBUGLEVEL_ell
^--------------------
}}}
I will check that it still happens with the latest pari/gp, and if so file
a bug report with Denis Simon.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/5204#comment:8>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
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