Internal and external ratio measurement method based on community structure, and community discovery method

The invention discloses an internal and external ratio measurement method based on a community structure, and a community discovery method. The internal and external ratio measurement method comprises the steps: firstly defining an internal and external ratio measurement standard which is used for judging whether a sub-network structure is a community or not, and the community closeness degree of the structure; secondly proposing a neighborhood bidirectional iteration algorithm, employing a group of initial sub-network structures after optimization, and carrying out the iteration to find a community based on the internal and external ratio measurement standard through increasing adjacent nodes or reducing internal nodes. According to the invention, the methods are used for quickly finding a community structure with high closeness degree in the network, can find a better community more quickly and completely, are earlier in the time of finding the best community by the 39.64% by average, enlarge the searching coverage by 12.67% by average, are low in calculating data dependence degree, and are suitable for distributed parallel calculation.