Thanks a lot for reporting! We *really* appreciate any feedback from
using Sage in classes: on bugs, designs and feature requests.
This bug is now #23433. I'll push a patch momentarily.
Best,
Johan Rosenkilde
Dima Pasechnik writes:
> On Thursday, July 13, 2017 at 11:43:18 AM UTC+1, David Joyner wrote:
>>
>> On Thu, Jul 13, 2017 at 5:59 AM, 'B. L.' via sage-devel
>> <sage-devel@googlegroups.com> wrote:
>> > Dear Sage-Developers,
>> >
>> > I'd like to report two issues that I came across when working with the
>> > coding theory classes of SAGE.
>> >
>> > The Sage Reference Manual: Coding Theory, Release 7.6 [1] explains on p.
>> 31:
>> > weight_enumerator [...] This is the bivariate, homogeneous polynomial in
>> 𝑥
>> > and 𝑦 whose coefficient to x^iy^{n-i} is the number of codewords of
>> > 𝑠𝑒𝑙𝑓 of Hamming weight 𝑖. Here, 𝑛 is the length of 𝑠𝑒𝑙𝑓.
>> > Actually, Sage returns another polynomial, namely the polynomial in 𝑥
>> and
>> > 𝑦 whose coefficient to x^{n-i}y^i is the number of codewords of
>> 𝑠𝑒𝑙𝑓 of
>> > Hamming weight 𝑖. (So the roles of x and y are interchanged).
>> > This can be directly with C.weight_enumerator?? in the example below
>> [2].
>> >
>> > I suggest to either change the description in the reference or to alter
>> the
>> > code in Sage.
>> >
>>
>> I'd propose just switching the x,y in the code:
>>
>> (1) On line 3503 of linear_code.py, change "return
>> sum(spec[i]*x**(n-i)*y**i for i in range(n+1))" to "return
>> sum(spec[i]*x**(i)*y**(n-i) for i in range(n+1))"
>>
>> (2) On line 3507, change "return sum(spec[i]*x**(n-i) for i in
>> range(n+1))" to "return sum(spec[i]*x**(i) for i in range(n+1))"
>>
>> (3) Some of the examples may change accordingly.
>>
>> This mistake could be my fault, since I wrote the original version
>> (long long ago). Unfortunately, I lack the git skills to submit a
>> patch.
>>
>> A patch can be produced by
>
> git diff > stuff.patch
>
> It would be great if you opened a ticket and posted this diff as an
> attachment...
>
>
>
>>
>> > The function weight_enumerator(bivariate=False) returns the evaluation
>> of
>> > the the above polynomial for y=1. Should't it be (in the current
>> version)
>> > the evaluation with x=1? In other words: Wouldn't one expect a
>> polynomial in
>> > x (or y) whose coefficient to x^i (or y^i) is the number of codewords of
>> > 𝑠𝑒𝑙𝑓 of Hamming weight 𝑖?
>> > The example below [2] illustrates my point: The code has four codewords,
>> one
>> > of weight 0, two of weight 3, one of weiht 4. Sage gives x^5 + 2*x^2 + x
>> as
>> > the univariate weight enumerator. I would have expected either 1 + 2*x^3
>> +
>> > x^4 or 1 + 2*y^3 + y^4.
>> >
>> > If you agree, I suggest to alter the code accordingly.
>> >
>> > Kind regards
>> > Barbara
>> > PS: I tested the code with Sage version 7.6 on an iMac.
>> >
>> >
>> > [1] http://doc.sagemath.org/pdf/en/reference/coding/coding.pdf
>> >
>> > [2] Sage code for the SageMathCell
>> >
>> > C= LinearCode(Matrix(GF(2),2,5, [[1,1,0,1,0], [0,0,1,1,1]]))
>> > print C.list()
>> > print C.spectrum()
>> > print C.weight_enumerator()
>> > print C.weight_enumerator(bivariate=False)
>> > C.weight_enumerator??
>> >
>> >
>> http://sagecell.sagemath.org/?z=eJxztlXwycxLTSxyzk9J1fBNLCnKrNBwd9Mw0tQx0jHVUYiONtQx1DEA4VggzwDMBMLYWE1NXq6Cosy8EgVnvZzM4hINJH5xQWpySVFpLrJYeWpmekZJfGpeaW5qUWJJfhF-yaTMssSizMSSVFu3xJziVKBaLKrs7QGIgD2K&lang=sage
>>
>> >
>> > --
>> > You received this message because you are subscribed to the Google
>> Groups
>> > "sage-devel" group.
>> > To unsubscribe from this group and stop receiving emails from it, send
>> an
>> > email to sage-devel+unsubscr...@googlegroups.com.
>> > To post to this group, send email to sage-devel@googlegroups.com.
>> > Visit this group at https://groups.google.com/group/sage-devel.
>> > For more options, visit https://groups.google.com/d/optout.
>>
--
You received this message because you are subscribed to the Google Groups
"sage-devel" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to sage-devel+unsubscr...@googlegroups.com.
To post to this group, send email to sage-devel@googlegroups.com.
Visit this group at https://groups.google.com/group/sage-devel.
For more options, visit https://groups.google.com/d/optout.
