Lucene中的评分机制，也是算一个相似度的问题，不过它采用的是计算向量间的夹角（余弦公式），在google黑板报中的：数学之美（余弦定理和新闻分类） 也有说明，可以通过余弦定理来判断相似度；于是决定自己动手试试。-Scoring mechanism in Lucene, also calculate a similarity problem, but it USES is the Angle between the vectors (cosine formula), in the Google blackboard: mathematical beauty (cosine theorem and classification of news) there are instructions, can be judged by cosine theorem similarity　He decided to try myself