#9247: A collection of little improvements to elliptic curves
-------------------------------+--------------------------------------------
Reporter: rlm | Owner: cremona
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-4.5
Component: elliptic curves | Keywords:
Author: Robert Miller | Upstream: N/A
Reviewer: John Cremona | Merged:
Work_issues: |
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Comment(by cremona):
OK, so the problem is that the warning output from the regulator call
appears in the wrong place in the output -- right?
I have solved this by avoiding it as follows. The gens() function uses
mwrank_lib (default) or mwrank_console to do a two-descent after
constructing the mwrank_EllipticCurve C. But it was failing to call the
saturate function on C. Some default saturation is done by the gens()
call (on C), but the default saturation bound is rather low (100, set in
eclib).
So I added a new parameter sat_bound to the gens() function in
ell_rational_field, default 1000, and made sure that both mwrank_lib and
mwrank_console option use it.
Now we have
{{{
sage: E = EllipticCurve([0, 0, 1, -79, 342])
sage: E.gens()
[(-10 : 11 : 1), (-39/4 : 105/8 : 1), (-8 : 21 : 1), (-7 : 23 : 1), (-6 :
24 : 1)]
}}}
{{{
sage: E = EllipticCurve([0, 0, 1, -79, 342])
sage: E.gens(algorithm='mwrank_console')
[(-10 : 11 : 1), (-39/4 : 105/8 : 1), (-8 : 21 : 1), (-7 : 23 : 1), (-6 :
24 : 1)]
}}}
compared with
{{{
sage: E = EllipticCurve([0, 0, 1, -79, 342])
sage: E.gens(sat_bound=100)
Saturation index bound = 265
WARNING: saturation at primes p > 100 will not be done;
points may be unsaturated at primes between 100 and index bound
Failed to saturate MW basis at primes [ ]
*** saturation possibly incomplete at primes [ ]
[(-10 : 11 : 1), (-39/4 : 105/8 : 1), (-8 : 21 : 1), (-7 : 23 : 1), (-6 :
24 : 1)]
}}}
I will post an additional patch in a minute.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9247#comment:8>
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