#12121: floor/ceil can be very slow at integral values
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Reporter: dsm | Owner: AlexGhitza
Type: defect | Status: needs_review
Priority: major | Milestone: sage-7.2
Component: basic arithmetic | Resolution:
Keywords: | Merged in:
Authors: Vincent Delecroix | Reviewers: Marc Mezzarobba
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/vdelecroix/12121 | 0e9b2f21d6a6bc42e35302316ac0f6b3b7451450
Dependencies: | Stopgaps:
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Comment (by vdelecroix):
Replying to [comment:41 vdelecroix]:
> Replying to [comment:39 mmezzarobba]:
> > * do we really need two loops that do essentially the same thing
(including raising errors with the exact same message)?
>
> The equality test is potentially costly. And we want to avoid it as much
as possible. In particular, it makes no sense to test this equality within
each step of the loop as it is in your version. On a related note, I
noticed that for `round` you need to test equality with elements of `ZZ +
1/2`.
And I also would like to use the very same function `incremental_rounding`
for elements of `QQbar`. For the very same reason, you only want very
lately the equality test.
--
Ticket URL: <http://trac.sagemath.org/ticket/12121#comment:42>
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