理解：http://www.shuang0420.com/2017/03/21/NLP%20%E7%AC%94%E8%AE%B0%20-%20%E5%86%8D%E8%B0%88%E8%AF%8D%E5%90%91%E9%87%8F/
模型代码参考：https://samaelchen.github.io/word2vec_pytorch/