#16880: further cleanup in arith.py/integer.pyx
-------------------------------------+-------------------------------------
       Reporter:  vdelecroix         |        Owner:
           Type:  enhancement        |       Status:  needs_review
       Priority:  major              |    Milestone:  sage-6.6
      Component:  number theory      |   Resolution:
       Keywords:                     |    Merged in:
        Authors:  Vincent Delecroix  |    Reviewers:
Report Upstream:  N/A                |  Work issues:
         Branch:                     |       Commit:
  u/vdelecroix/16880                 |  25176c520e538f0a98334c7ffdfe69c14207b32d
   Dependencies:  #16878, #17852     |     Stopgaps:
-------------------------------------+-------------------------------------
Changes (by vdelecroix):

 * status:  needs_work => needs_review


Old description:

> This ticket introduces several changes:
>  - introduce a method `next_prime_power` for integers
>  - make `prime_powers` an iterator (using `next_prime_power`) so that it
> can be used for large integers as well
>  - create a much faster cythonized `prime_power_range`
>
> We get a little speed down for the iteration over `prime_powers` but we
> can now do
> {{{
> sage: for p in prime_powers(2**100, 2**100+500):
> ....:     print p
> 1267650600228229401496703205376
> 1267650600228229401496703205653
> 1267650600228229401496703205707
> 1267650600228229401496703205823
> }}}
> The cython function `prime_power_range` is much faster than the previous
> `prime_powers` (around x4 in the timings).
>
> Since #16878, 1 is not a prime power anymore! So we fix `prime_powers` to
> never return 1 in its output.

New description:

 In this ticket we:
  - introduce methods `previous_prime`, `next_prime_power`,
 `previous_prime_power` for integers
  - split `prime_range` in `rings/fast_arith.pyx` into two subfunctions and
 optimize them
  - create a faster cythonized `prime_power_range` and propose two
 implementations for `arith.prime_powers`
  - add `rings/fast_arith.pyx` to the documentation

--

--
Ticket URL: <http://trac.sagemath.org/ticket/16880#comment:14>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica, 
and MATLAB

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