These indicators are indicators to measure the search engine algorithm. Search engines generally use the method of PI (peritem) for evaluation, which simply means to grade the search results one by one. Suppose we search for a word on Google now and get 5 results. We classify these results into 3 grades: Good (good), Fair (general), and Bad (bad), and then give them scores of 3, 2, and 1 respectively. Let's give an example to follow this rating.
CG (Cumulative Gain) cumulative income
CG is the predecessor of DCG. It does not consider the position information in the search results, but only considers the sum of the corresponding scores of all the results in the search result list. If there are P results in the search result list, the formal definition of CG is:
DCG (Discounted cumulative gain) discount cumulative income
NDCG (Normalize DCG) normalized discount cumulative income
Other cases
Rotor: https://www.cnblogs.com/datasnail/p/13088964.html
Reference: https://www.cnblogs.com/ywl925/archive/2012/11/21/2780861.html