#9322: long time in simon_two_descent for elliptic curves
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Reporter: cremona | Owner: AlexGhitza
Type: defect | Status: needs_info
Priority: major | Milestone: sage-4.7.2
Component: elliptic curves | Keywords: Simon ecc2011
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
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Changes (by zimmerma):
* keywords: Simon => Simon ecc2011
Comment:
ok, I found where the problem comes from. In the file {{{ellQ.gp}}} which
is also loaded by the
{{{gp_simon.py}}} file, the global constants {{{LIM1, LIM3, LIMTRIV}}}
have different values than
in {{{ell.gp}}}, respectively 5, 50, 50 instead of 2, 4, 2.
The slow behaviour can be reproduced with {{{sage -gp}}} if one reads both
{{{ell.gp}}}
*and* {{{ellQ.gp}}}. If one only reads {{{ell.gp}}}, it is fast.
Apparently {{{ellQ.gp}}} is not
needed for this computation.
Moreover the default values in Sage are again different: 5, 50, 10.
With 5, 5, 10 it takes only 1.45s (wall clock time) on my laptop.
With 5, 10, 10 it takes 2.19s.
With 5, 20, 10 it takes 11.63s.
Note that those values should be modified both in
{{{ell_number_field.py}}} and in
{{{gp_simon.py}}} (the former function is critical in this example).
One should also share the default values for {{{lim1, lim3, limtriv}}}
between the
{{{simon_two_descent}}} functions in {{{ell_number_field.py}}} and
{{{gp_simon.py}}}.
Paul
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9322#comment:9>
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