#12265: massively optimize f.change_ring(QQ) for f in ZZ['x']
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   Reporter:  was          |          Owner:  tbd     
       Type:  enhancement  |         Status:  new     
   Priority:  major        |      Milestone:  sage-5.0
  Component:  performance  |       Keywords:          
Work_issues:               |       Upstream:  N/A     
   Reviewer:               |         Author:          
     Merged:               |   Dependencies:          
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Description changed by was:

Old description:

> I needed to massively optimize f.change_ring(QQ) for f in ZZ['x'] so that
> #11375 would not suck.

New description:

 I needed to massively optimize f.change_ring(QQ) for f in ZZ['x'] so that
 #11375 would not suck.

 For me,
 {{{
 BEFORE:
 sage: R.<x> = ZZ[]; v = [1..10^6]; f = R(v);
 sage: time g = f.change_ring(QQ)
 Time: CPU 4.39 s, Wall: 4.39 s
 sage: R.<x> = ZZ[]; v = [1..10^3]; f = R(v);
 sage: timeit('g = f.change_ring(QQ)')
 125 loops, best of 3: 1.79 ms per loop

 AFTER:
 sage: R.<x> = ZZ[]; v = [1..10^6]; f = R(v);
 sage: time g = f.change_ring(QQ)
 Time: CPU 0.05 s, Wall: 0.05 s
 sage: R.<x> = ZZ[]; v = [1..10^3]; f = R(v);
 sage: timeit('g = f.change_ring(QQ)')
 625 loops, best of 3: 107 µs per loop
 }}}

 So we get nearly a 100-fold speedup.

 }}}

--

-- 
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12265#comment:1>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica, 
and MATLAB

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