#4260: use LinBox as native matrix representation for dense matrices over GF(p)
------------------------------------+---------------------------------------
   Reporter:  malb                  |          Owner:  cpernet                  
                 
       Type:  enhancement           |         Status:  needs_review             
                 
   Priority:  major                 |      Milestone:  sage-4.7.2               
                 
  Component:  linear algebra        |       Keywords:  linbox, linear algebra, 
sd32              
Work_issues:  extend documentation  |       Upstream:  N/A                      
                 
   Reviewer:                        |         Author:  Burcin Erocal, Martin 
Albrecht, Rob Beezer
     Merged:                        |   Dependencies:                           
                 
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Comment(by malb):

 I adapted the crossover from {{{float}}} to {{{double}}}. Around 2^11^
 {{{Modular<float>}}}} is '''really''' slow because there are not enough
 bits left to let ATLAS do it's magic, i.e., too many modular reductions.
 On my computer using {{{Modular<float>}}} up to 2^8^ seems like a good
 choice. On sage.math this choice isn't too bad (but not optimal).
 Multiplying two 1,000 x 1,000 matrices over GF(p) (2nd column) which is
 smaller than 2^i^ (1st column) and the time it takes:

 {{{
  2          3 0.22000
  3          7 0.24000
  4         13 0.24000
  5         31 0.25000
  6         61 0.26000
  7        127 0.26000
  8        251 0.62000
  9        509 0.38000 <=== using Modular<double> now
 10       1021 0.38000
 11       2039 0.39000
 12       4093 0.39000
 13       8191 0.40000
 14      16381 0.41000
 15      32749 0.41000
 16      65521 0.42000
 17     131071 0.43000
 18     262139 0.43000
 19     524287 0.44000
 20    1048573 0.44000
 21    2097143 0.45000
 22    4194301 0.66000
 23    8388593 1.91000 <=== Generic matrices
 }}}

-- 
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/4260#comment:15>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica, 
and MATLAB

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