Wasserstein距离

https://blog.csdn.net/leviopku/article/details/81388306

https://blog.csdn.net/nockinonheavensdoor/article/details/82055147

https://blog.csdn.net/c9Yv2cf9I06K2A9E/article/details/80016095

知乎：https://zhuanlan.zhihu.com/p/26988777