#9882: slow random_element() for integer mod ring
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Reporter: dmharvey | Owner: tbd
Type: defect | Status: new
Priority: major | Milestone:
Component: performance | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Comment (by ppurka):
Replying to [comment:4 mmezzarobba]:
> Thanks for your reply, and... sorry for being thick, but I still don't
understand! I get:
> {{{
> sage: %timeit ZZ.random_element(0, R.order()-1)
> 1000000 loops, best of 3: 650 ns per loop
> sage: a = (R.order()-1)
> sage: %timeit R(a)
> 1000000 loops, best of 3: 325 ns per loop
> sage: a = (R.order()-1)//2
> sage: %timeit R(a)
> 1000000 loops, best of 3: 324 ns per loop
> }}}
> so I would hope for a total running time of the order of 1 µs + some
overhead for my function
With the `//` operator you are actually getting Sage integers, whereas I
was getting Sage rationals with the `/` operator. That explains why the
coercion to `Integers` was taking so much time.
Perhaps the best way is to use gmp as you have done above.
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Ticket URL: <http://trac.sagemath.org/ticket/9882#comment:6>
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