[GAP Forum] about automorphism group of linear codes

[Joe Fields]

Dear Tam Van,

See section 4.4.3 of the Guava 3.10 manual for an extended example.

Given a relatively small linear code C, simply use

gap> AutomorphismGroup(C);

Depending on your operating system, the AutomorphismGroup function
may use an external program written in C by Jeffrey S. Leon, or a
function written in the GAP language called
"PermutationAutomorphismGroup"

The latter function is much slower than the one written by Leon, but if
you are interested in the mechanics of what is going on to calculate a
code's automorphism group, looking at the source code for
PermutationAutomorphismGroup is vastly easier.  The source code for both
approaches is in the Guava package's directory tree.  

Leon's C code is in the src/leon subdirectory and the other one is in
lib/codeops.gi

Hope that helps!

Best wishes,
Joe Fields
  
On Mon, 2011-10-24 at 22:29 -0400, Vo Tam Van wrote:
> Hi every body
> 
> I am looking for the source code of computing the automorphism group
> of linear code. For example, the binary linear code
> C = { [0,0,0,0]; [0,0,1,1]; [1,1,0,0]; [1,1,1,1]} has the permutation
> group of order 8. Please teach me how to write GAP program to
> compute automorphism of linear code C. Any comments and helps are
> highly appreciated. Thanks alot.
> 
> Tam Van
> 
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-- 
Joseph E. Fields, PhD
Mathematics Department
Southern Connecticut State University
http://www.southernct.edu/~fields