the matlab program checks for cycles that are of the legnth 4.it is a useful program to check if the cycles in your LDPC code are to short thus causing BER errors

matrix for channel coding with ldpc and ldgm and free 4-cycle

有循环检测，周期性检测，采用累计贡献率的方法，ldpc码的编解码实现。- There are cycle detection, periodic testing, The method of cumulative contribution rate Codec ldpc code implementatio.