#11767: elliptic_logarithm of high precision points often hangs forever
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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: | Author:
Merged: | Dependencies:
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Comment(by leif):
Replying to [comment:9 zimmerma]:
> John, if you change {{{eps}}} to {{{2^(-prec2+1)}}} instead of
{{{2^(-prec2)}}} then the case
> where {{{r = 1 - 2^(-prec2)}}} will also terminate with the < condition.
But the case where
> {{{r = 1 + 2^(-prec2+1)}}} will still loop.
Well, either `r.abs()` converges to one, or it doesn't. So if you compute
with sufficiently high precision, especially not choosing epsilon to be
the minimal positive value of the floating point type used, the
termination condition will get true after some iterations.
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11767#comment:10>
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