本程序可检验所设计的LDPC码中的4环个数。LDPC码中的4环决定LDPC码的解码算法是否能够快速收敛，见程序前言中的参考文献。

LDPC码为高性能信道纠错码，已被DVB-s2和IEEE802.16e采纳。-This procedure can be designed to test the LDPC code in ring number 4. LDPC code of 4 Central decision LDPC code decoding algorithm is able to fast convergence, see the foreword in the program references. LDPC codes for high-performance error-correcting code channel has been DVB-s2 and IEEE802.16e adopted.