#13065: simon_two_descent not working
-----------------------------------------------------------+----------------
Reporter: alexc | Owner:
cremona
Type: defect | Status:
new
Priority: major | Milestone:
sage-5.0.1
Component: elliptic curves | Resolution:
Keywords: EllipticCurve simon_two_descent gp pari | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by fwclarke):
As well as the problem with the gp script, there are errors in the sage
code which meant that the gp error didn't get reported as was intended:
At line 283 of `schemes/elliptic_curves/ell_number_field.py` (Sage-5.0):
{{{
prob_rank = Integer(t[0])
}}}
`t` has the value `'fail'`, from the previous line. But the error should
have been detected earlier. If lines 104--105 of
`schemes/elliptic_curves/gp_simon.py`:
{{{
if s.find("###") != -1:
raise RuntimeError, "%s\nAn error occurred while running Simon's
2-descent program"%s
}}}
are changed to:
{{{
if s.find("***") != -1:
raise RuntimeError, "\n%s\nAn error occurred while running Simon's
2-descent program"%s
}}}
then:
{{{
sage: K = CyclotomicField(43).subfields(3)[0][0]
sage: E = EllipticCurve(K, '37')
sage: E.simon_two_descent()
Traceback (most recent call last):
...
RuntimeError:
*** at top-level: ans=bnfellrank(K,[0,0,1,
*** ^--------------------
*** in function bnfellrank: ...eqtheta,rnfeq,bbnf];rang=
*** bnfell2descent_gen(b
*** ^--------------------
*** in function bnfell2descent_gen: ...riv,r=nfsqrt(nf,norm(zc))
*** [1];if(DEBUGLEVEL_el
*** ^--------------------
*** array index (1) out of allowed range [none].
An error occurred while running Simon's 2-descent program
}}}
There's another error at line 276 of
`schemes/elliptic_curves/ell_number_field.py`, where a `KeyError` has to
be allowed for as well as an `AttributeError`. Thus trying
`E.simon_two_descent()` again leads to
{{{
sage: E.simon_two_descent()
Traceback (most recent call last):
...
KeyError: (5, 50, 10, 20, 30)
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13065#comment:3>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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