#13596: Improvements to IntegerMod is_square
-------------------------------+-------------------------------------------
       Reporter:  roed         |        Owner:  AlexGhitza
           Type:  enhancement  |       Status:  needs_work
       Priority:  major        |    Milestone:  sage-pending
      Component:  basic        |   Resolution:
  arithmetic                   |    Merged in:
       Keywords:               |    Reviewers:  Francis Clarke, Peter Bruin
        Authors:  David Roe    |  Work issues:
Report Upstream:  N/A          |       Commit:
         Branch:               |     Stopgaps:
   Dependencies:  #12415       |
-------------------------------+-------------------------------------------
Changes (by pbruin):

 * status:  needs_review => needs_work
 * reviewer:  Francis Clarke => Francis Clarke, Peter Bruin


Comment:

 The patch did not apply anymore due to the fact that the `pari()` method
 was renamed to `_pari_()`.  I fixed this, and then did the following
 (inspired by the new doctest):
 {{{
 #!python
 def test_native():
     for p,q,r in cartesian_product_iterator([[3,5],[11,13],[17,19]]):
         for ep,eq,er in
 cartesian_product_iterator([[0,1,2,3],[0,1,2,3],[0,1,2,3]]):
             for e2 in [0,1,2,3,4]:
                 n = p^ep*q^eq*r^er*2^e2
                 for _ in range(2):
                     a = Zmod(n).random_element()
                     b = a.is_square()

 def test_pari():
     for p,q,r in cartesian_product_iterator([[3,5],[11,13],[17,19]]):
         for ep,eq,er in
 cartesian_product_iterator([[0,1,2,3],[0,1,2,3],[0,1,2,3]]):
             for e2 in [0,1,2,3,4]:
                 n = p^ep*q^eq*r^er*2^e2
                 for _ in range(2):
                     a = Zmod(n).random_element()
                     b = bool(a._pari_().issquare())
 }}}
 I got the following timings:
 {{{
 sage: %timeit test_native()
 1 loops, best of 3: 3.11 s per loop
 sage: %timeit test_pari()
 1 loops, best of 3: 2.98 s per loop
 }}}
 From the perspective of someone who does not want to reinvent the wheel,
 this suggests that we should just call PARI instead of using a native Sage
 implementation.

--
Ticket URL: <http://trac.sagemath.org/ticket/13596#comment:8>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica, 
and MATLAB

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