#17088: PeriodicRegion.__div__: use integer arithmetic
-----------------------------------+------------------------
       Reporter:  jdemeyer         |        Owner:
           Type:  defect           |       Status:  new
       Priority:  critical         |    Milestone:  sage-6.4
      Component:  elliptic curves  |   Resolution:
       Keywords:                   |    Merged in:
        Authors:  Jeroen Demeyer   |    Reviewers:
Report Upstream:  N/A              |  Work issues:
         Branch:                   |       Commit:
   Dependencies:                   |     Stopgaps:
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Description changed by jdemeyer:

Old description:

> Replace the unreliable floating-point arithmetic in
> `PeriodicRegion.__div__` by pure integer arithmetic.
>
> Note that I don't understand the purpose of the code, I just want to fix
> the fact that the results are not reproducible.
>
> == Background ==
> this is causing doctest failures in #16938 due to slightly different
> floating-point rounding. The failure is the following:
> {{{
> sage -t src/sage/schemes/elliptic_curves/period_lattice_region.pyx
> **********************************************************************
> File "src/sage/schemes/elliptic_curves/period_lattice_region.pyx", line
> 395, in
> sage.schemes.elliptic_curves.period_lattice_region.PeriodicRegion.__div__
> Failed example:
>     (S / 3).plot()
> Expected:
>     Graphics object consisting of 109 graphics primitives
> Got:
>     Graphics object consisting of 121 graphics primitives
> **********************************************************************
> }}}
> (this output of `plot()` commands was added by #16746). As you can see,
> there are more pixels in the debug version.

New description:

 Replace the unreliable floating-point arithmetic of
 `PeriodicRegion.__div__` in
 `src/sage/schemes/elliptic_curves/period_lattice_region.pyx` by pure
 integer arithmetic.

 Note that I don't understand the purpose of the code, I just want to fix
 the fact that the results are not reproducible.

 == Background ==
 this is causing doctest failures in #16938 due to slightly different
 floating-point rounding. The failure is the following:
 {{{
 sage -t src/sage/schemes/elliptic_curves/period_lattice_region.pyx
 **********************************************************************
 File "src/sage/schemes/elliptic_curves/period_lattice_region.pyx", line
 395, in
 sage.schemes.elliptic_curves.period_lattice_region.PeriodicRegion.__div__
 Failed example:
     (S / 3).plot()
 Expected:
     Graphics object consisting of 109 graphics primitives
 Got:
     Graphics object consisting of 121 graphics primitives
 **********************************************************************
 }}}
 (this output of `plot()` commands was added by #16746). As you can see,
 there are more pixels in the debug version.

--

--
Ticket URL: <http://trac.sagemath.org/ticket/17088#comment:2>
Sage <http://www.sagemath.org>
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