#4075: bug in BCHCode
---------------------------+------------------------------------------------
Reporter: wdj | Owner: rlm
Type: defect | Status: new
Priority: major | Milestone:
Component: coding theory | Keywords:
---------------------------+------------------------------------------------
This was reported by Felipe Voloch:
{{{
Hi,
I am not sure how to report bugs in Sage but I see you are involved
with their coding theory. I was playing around with BCH codes and
in particular I wanted the BCH code over F_5 of length 26 and designed
distance 5. Sage reports this code as having dimension 25 (see below)
but the dimension should be 10, which Magma computes correctly (see
below also).
Thanks
Felipe
---------------------SAGE---------------------------------------------
amd13:~> sage
----------------------------------------------------------------------
| SAGE Version 3.0.5, Release Date: 2008-07-11 |
| Type notebook() for the GUI, and license() for information. |
----------------------------------------------------------------------
sage: C = BCHCode(26,5,GF(5)); C
Linear code of length 26, dimension 25 over Finite Field of size 5
---------------------MAGMA--------------------------------------------
linux182~> magma
Magma V2.14-10 Fri Sep 5 2008 14:24:48 on linux182 [Seed = 1390124479]
Type ? for help. Type <Ctrl>-D to quit.
> > C:=BCHCode(GF(5),26,5);
> > Dimension(C);
10
}}}
Incidently, Guava does this correctly. The problem is that I used the
wrong element to construct the generator polynomial.
This is fixed in the attached patch, based on 3.1.2.alpha4. It passes sage
-testall and also adds a test in the docstring to include the example
reported by Felipe.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/4075>
SAGE <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
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