seek_fourcycle.m

ldpc编码

function [cycle_position_all find_four]=seek_fourcycle(H,p)
% H=[1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0;
%    0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0;
%    0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0;
%    0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0;
%    0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1;
%    1 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 1 0;
%    0 1 0 0 0 0 0 1 0 0 1 0 0 0 0 0 0 0 0 1;
%    0 0 1 0 0 0 0 0 1 0 0 1 0 0 0 1 0 0 0 0;
%    0 0 0 1 0 0 0 0 0 1 0 0 1 0 0 0 1 0 0 0;
%    0 0 0 0 1 1 0 0 0 0 0 0 0 1 0 0 0 1 0 0;
%    1 0 0 0 0 0 0 0 1 0 0 0 1 0 0 0 0 0 0 1;
%    0 1 0 0 0 0 0 0 0 1 0 0 0 1 0 1 0 0 0 0;
%    0 0 1 0 0 1 0 0 0 0 0 0 0 0 1 0 1 0 0 0;
%    0 0 0 1 0 0 1 0 0 0 1 0 0 0 0 0 0 1 0 0;
%    0 0 0 0 1 0 0 1 0 0 0 1 0 0 0 0 0 0 1 0];
[m,n]=size(H);
%S=[0 0 0 0;0 4 1 2;0 2 3 1];
%p=5;
cycle_position_all=[];find_four=0;
for l=1:m-p
    l;
    h_r=H(l,:);
    r_index=find(h_r);
    L_r=length(r_index);
    for i=1:L_r-1
        i;
        for j=i+1:L_r
            j;
            h_c=H(l+1:end,r_index(j));
            c_index=find(h_c);
            c_index=c_index+l;
            L_c=length(c_index);
            for k=1:L_c
                k;
                if H(c_index(k),r_index(i))==1
                    cycle_position=[l r_index(i);l r_index(j);c_index(k) r_index(j);c_index(k) r_index(i)];
                    cycle_position_all=[cycle_position_all cycle_position];
                    find_four=find_four+1;
                end
            end    
        end
    end
end