#19152: {Real,Complex}Ball: Miscellaneous fixes and improvements
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Reporter: mmezzarobba | Owner:
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-6.10
Component: numerical | Resolution:
Keywords: | Merged in:
Authors: Marc Mezzarobba | Reviewers: Clemens Heuberger
Report Upstream: N/A | Work issues:
Branch: public/19152-arb- | Commit:
misc | 7e6b5d049ce0107880171d156f3da2f16d480476
Dependencies: #19063 | Stopgaps:
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Comment (by mmezzarobba):
Replying to [comment:35 jdemeyer]:
> > Identical RealBall objects are understood to give permission for
algebraic simplification. This assumption is made to improve performance.
For example, setting z = x*x sets z to a ball enclosing the set {t2:t∈x}
and not the (generally larger) set {tu:t∈x,u∈x}.
>
> I'm not sure that we should do that. It's not what intervals do: I would
expect `x*x` to be different from `x^2`.
Replying to [comment:36 jdemeyer]:
> I consider this a bug:
> > It is possible to construct a ball whose parent is the real ball field
with precision p but whose midpoint does not fit on p bits. However, the
results of operations involving such a ball will (usually) be rounded to
its parent’s precision.
>
> It causes too much confusion for example with the `round()` function.
It's also too different from all other places in Sage which handle
precision.
Both these design choices were discussed on previous arb-related tickets,
in particular #17194. As far as I'm concerend, I'm happy with the way
things currently work (even though I was a little bit skeptical at first),
and I'm not interested in working on changing it. Incidentally, I'm not
sure this ticket would be the right place.
--
Ticket URL: <http://trac.sagemath.org/ticket/19152#comment:40>
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