koetter_vardy.m

在matlab中

function M = koetter_vardy(P,s)

% M = KOETTER_VARDY(P,s)
%
% Generate interpolation points and multiplicities for
% soft-decision decoding of Reed-Solomon codes using the
% Guruswami-Sudan algorithm.  The algorithm is described in the
% paper "Algebraic Soft-Decision Decoding of Reed-Solomon Codes" by
% R. Koetter and A. Vardy in the IEEE Transactions on Information
% Theory, November 2003.
%
% The inputs are P, the reliability matrix, and s, the number of
% interpolation points in total.  The function outputs M, a
% multiplicity matrix.

q = size(P,1);
m = log2(q);
n = size(P,2);

Pstar = P;
M = zeros(q,n);

for ind1=1:s
  pij = max(max(Pstar));
  [Is, Js] = find(Pstar==pij);
  row = Is(1);
  col = Js(1);
  Pstar(row,col) = pij/(M(row,col) + 2);
  M(row,col) = M(row,col) + 1;  
end