#11767: elliptic_logarithm of high precision points often hangs forever
--------------------------------------------+-------------------------------
Reporter: was | Owner: cremona
Type: defect | Status: needs_review
Priority: major | Milestone: sage-4.7.2
Component: elliptic curves | Keywords:
Work_issues: | Upstream: N/A
Reviewer: John Cremona, Leif Leonhardy | Author: Paul Zimmermann
Merged: | Dependencies:
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Comment(by cremona):
Try this:
{{{
sage: K.<a> = QuadraticField(-5)
sage: E = EllipticCurve([1,1,a,a,0])
sage: P = E(0,0)
sage: P.order()
+Infinity
sage: L = P.curve().period_lattice(K.embeddings(ComplexField())[0])
sage: time L.elliptic_logarithm(P, prec=500)
1.17058357737548897849026170185581196033579563441850967539191867385734983296504066660506637438866628981886518901958717288150400849746892393771983141354
-
1.13513899565966043682474529757126359416758251309237866586896869548539516543734207347695898664875799307727928332953834601460994992792519799260968053875*I
Time: CPU 0.35 s, Wall: 0.36 s
sage: L = P.curve().period_lattice(K.embeddings(ComplexField(1000))[0])
sage: time L.elliptic_logarithm(P, prec=1000)
}}}
The last line hangs with vanilla 4.7.1. prec=900 is still OK. Note that
it is irrelevant to specify the precision when constructing the period
lattice, since the only use made of the embedding at that stage is to
determine which emebedding is required; the elliptic log computation is
where the floating point work is done.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11767#comment:20>
Sage <http://www.sagemath.org>
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