#16116: Multiplication of dense cyclotomic matrices should be faster
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       Reporter:  jipilab                        |        Owner:
           Type:  enhancement                    |       Status:  new
       Priority:  major                          |    Milestone:  sage-6.4
      Component:  number fields                  |   Resolution:
       Keywords:  cyclotomic field, matrix,      |    Merged in:
  multiplication, benchmark, days57              |    Reviewers:
        Authors:                                 |  Work issues:
Report Upstream:  N/A                            |       Commit:
         Branch:                                 |     Stopgaps:
   Dependencies:                                 |
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Comment (by was):

 Replying to [comment:7 vdelecroix]:
 > Hello,
 >
 > I reformatted your example such that they fit in less lines (it can
 easily switched back to your original version if you do not like it).
 >
 > I had a quick look at the code for dense cyclotomic matrices. The
 implementation is quite old and uses a lot of reduction mod p (even for
 multiplication). The code calls a lot of Python code like creating a
 finite field, creating a matrix space, etc which are relatively slow
 compared to a small matrix multiplication. Did you try multiplying larger
 matrices (i.e. 10x10 or 15x15)?

 I designed and implemented the algorithm for dense cyclotomic matrices.
 We were optimizing for larger matrices... which in the context of modular
 forms means at least 100 rows (and often much, much more).   GAP/pari on
 the other hand optimize for relatively tiny matrices.   The asymptotically
 fast algorithms for large matrices are totally different than for small...

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Ticket URL: <http://trac.sagemath.org/ticket/16116#comment:8>
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