#10590: Saturation of elliptic curve points can cause an infinite loop
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Reporter: cremona | Owner: cremona
Type: defect | Status: needs_review
Priority: major | Milestone:
Component: elliptic curves | Keywords: saturation
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Changes (by cremona):
* cc: was (added)
* status: new => needs_review
Comment:
Problem fixed.
I added a function mwrank_get_precision() (by wrapping eclib's existing
decimal_precision() function). Testing revealed that
mwrank_set_precision(mwrank_get_precision()) had the effect of reducing
the precision by at least 1 (exactly on for precision<803, the getting
worse) on account or rounding errors in the conversion to/from base 2/base
10. That is fixed by adding some code to the wrapper function for
set_precision().
This new functionality is used in the saturation() function to catch
failures due to lack of precision and gradually increase the precision
until success is gained. At the end the precision is put back to what it
was.
In all the above, "precision" only refers to the floating point precision
used by the NTL library withing eclib, not to anything else in Sage.
Patch has been tested on a 64-bit machine on the whole library (including
long tests).
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10590#comment:1>
Sage <http://www.sagemath.org>
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