#8212: arithmetic on GF(2^n) might be improved
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   Reporter:  zimmerma          |       Owner:  zimmerma       
       Type:  enhancement       |      Status:  positive_review
   Priority:  minor             |   Milestone:  sage-4.3.3     
  Component:  basic arithmetic  |    Keywords:                 
     Author:                    |    Upstream:  N/A            
   Reviewer:                    |      Merged:                 
Work_issues:                    |  
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Changes (by zimmerma):

  * status:  needs_review => positive_review


Comment:

 ok, I give a positive review for that ticket, and will review #8220
 afterwards. Great work!

 Paul

 PS: a related question is the following over GF(2): when no irreducible
 trinomial exists for a
 given degree n, instead of using a pentanomial, one can use an "almost
 irreducible" trinomial,
 i.e., a trinomial x^n+d^+x^s^+1 which has an irreducible factor of degree
 n. For example for
 n=211, x^214^+x^103^+1 works. I tried this with QuotientRing, but it is
 much slower:
 {{{
 R.<x> = PolynomialRing(GF(2),x)
 T.<x> = QuotientRing(R, x^214 + x^103 + 1)

 def bar(n):
    f = x
    for i in range(n):
       f = f^2
    return f
 sage: %timeit bar(10000)
 10 loops, best of 3: 191 ms per loop
 }}}

-- 
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8212#comment:9>
Sage <http://www.sagemath.org>
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