#19422: A new structure for Punctured Codes
-------------------------------------+-------------------------------------
Reporter: dlucas | Owner:
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-7.2
Component: coding theory | Resolution:
Keywords: | Merged in:
Authors: David Lucas | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/dlucas/punctured_code | 36e71c57401929089bc1938aa016b251b54f8916
Dependencies: #19653 | Stopgaps:
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Changes (by jlavauzelle):
* status: needs_review => needs_work
Comment:
Hi David,
A few remarks -- the last ones, I hope:
- in `structured_representation` method: it doesn't work when one
concatenates puncturings. For example, the following script
{{{
C = codes.GeneralizedReedSolomonCode(GF(7).list(), 4)
P = codes.PuncturedCode(C, [0,6])
D = P.structured_representation()
P2 = codes.PuncturedCode(P, [0,4])
D2 = P2.structured_representation()
}}}
fails at fifth line (so double puncturing actually works, only
`structured_representation` crashes). From the crash log, it seems that
you don't build the right set of `pts`.
- in `PuncturedCodePuncturedMatrixEncoder`, one can construct this encoder
while passing as argument a code which is not a punctured one. As a direct
consequence, this scripts fails:
{{{
C = codes.GeneralizedReedSolomonCode(GF(7).list(), 4)
E = codes.encoders.PuncturedCodePuncturedMatrixEncoder(C)
G = E.generator_matrix()
}}}
The question is: is it the user's mistake, or should the code handle it ?
Maybe it's reasonable to throw an error.
- same remark for your decoder: one can pass a non-punctured code as
parameter.
- in `__init__` function of `PuncturedCodeOriginalCodeDecoder`, maybe it
is better to use `True/False` boolean values instead of `error_erasure =
0` and `error_erasure = 1`.
- I also prefer the compact notation:
{{{
e_list = [ one if i in pts else zero for i in range(Cor.length()) ]
}}}
instead of:
{{{
e_list = []
for i in range(Cor.length()):
if i in pts:
e_list.append(one)
else:
e_list.append(zero)
}}}
- finally, a typo, l.441 : default instead of dafault
I did not perform exhaustive tests of all the combinations of
codes/encoders/decoders/strategies, because it is too long. So given the
complexity of the feature you're trying to implement, it's still possible
there remains some minor errors -- especially with extreme settings -- but
maybe a real deep use of this class (by actual users) could make them
appear more easily.
Thus, when you're done fixing the previous errors, I give the green light.
Julien
--
Ticket URL: <http://trac.sagemath.org/ticket/19422#comment:34>
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