On Sat, Dec 06, 2008 at 01:38:49PM +0100, Marco Maso wrote:
> Please note that n=262128 can be obtained with a primitive polynomial
> of grade 18 (n^18=262144) so we are far from GF(31) or GF(63) limit...
> The grade of the generator is 168 as n-k=168 (so again its grade is
> bigger than the primitive's).
Then there is an artifical limit in the BCH code as it forces n-k < 31..
Check the gf.cc code in the bchenco and bchdeco functions. There are
several issues in this case. Firstly,
if ((n < 3) || (nn < k) || (m > __OCTAVE_GALOIS_MAX_M)) {
error ("bchenco: invalid values of message or codeword length");
return retval;
}
should have the limit on m > __OCTAVE_GALOIS_MAX_M removed, and things
like
genpoly = galois(args(i).matrix_value (), m);
and all definitions of "galois" types in these functions, should
probably be in GF(2) and not GF(2^m) as the above will do, so write the
above as
genpoly = galois(args(i).matrix_value (), 1);
etc.. I have no time to look at this, but if you are confident of what
you say, the above changes should work.
D.
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