#19653: New decoders for Generalized Reed-Solomon codes
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Reporter: dlucas | Owner:
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-7.1
Component: coding theory | Resolution:
Keywords: | Merged in:
Authors: David Lucas | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/dlucas/grs_decoders | 4aebb5a23a3c571f945bb7da558e03ff4b4c1ace
Dependencies: #18928, #19897 | Stopgaps:
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Comment (by jlavauzelle):
Hi David,
I found a weird thing in your functions `_partial_xgcd()` :
- in Key equation decoder, you define a `stop` variable, but never use
it; your halting condition is related to the polynomial `t`, contrary to
what you say in your documentation.
- in Gao decoder, you use a variable `stop` which (I think, though Gao
paper is not so clear about it) isn't well-defined. You write: `stop =
floor(self.code().dimension() + self.code().length()) / 2`; I think that's
`stop = (self.code().dimension() + self.code().length()) // 2` instead
(note the integer division).
Apparently, it could solve the previous "too-high degree re-encoding"
issue.
You also told me to point out when you used numbers instead of field
elements. Here is a small list (I don't know if all of them belong to your
code):
- l. 197: `0 in ...` --> `F.zero()`
- l. 317: maybe the 1/...
- l. 1702: `e.append(0)` --> `e.append(C.base_ring().zero())`. Maybe
also the previous 1 and 0 in lines 1698 and 1699.
Otherwise, the code is pretty good. I've nothing to add.
Julien
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Ticket URL: <http://trac.sagemath.org/ticket/19653#comment:25>
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