#19623: Syndrome decoder is not a syndrome decoder
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       Reporter:  dlucas             |        Owner:
           Type:  enhancement        |       Status:  needs_review
       Priority:  major              |    Milestone:  sage-7.0
      Component:  coding theory      |   Resolution:
       Keywords:                     |    Merged in:
        Authors:  David Lucas        |    Reviewers:
Report Upstream:  N/A                |  Work issues:
         Branch:                     |       Commit:
  u/dlucas/generic_decoders          |  fc79446d6948143d32a9065410453379c79ef2b2
   Dependencies:                     |     Stopgaps:
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Comment (by dlucas):

 > Since the covering radius of a linear code is always at most n-k, does
 it make any sense to let the table search beyond that?

 Not really. I'll change this.

 > Did you prove that if there are no coset leaders of weight t, then there
 are no coset leaders of t+1? (i.e. that your early termination is sound)

 It comes from theorem 1.12.6, prop. 5 in Huffman and Pless

 Theorem 1.12.6 Let C be an [n, k] code over F q . Let C*
 a code obtained from C by puncturing on some coordinate. The following
 hold:

 (v) Assume that x is a coset leader of C. If x' ∈ `(F_q)^n` all of whose
 nonzero components agree
 with the same components of x, then x' is also a coset leader of C. In
 particular, if
 there is a coset of weight s, there is also a coset of any weight less
 than s.

--
Ticket URL: <http://trac.sagemath.org/ticket/19623#comment:8>
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