(1)Dimensionality Reduction: A Comparative Review的P15页The presence of free parameters has both advantagesand disadvantages. The main advantage of the presence of free parameters is that they provide more flexibility to the technique, whereas their main disadvantage is that they need to be tuned to optimize the performance of the dimensionality reduction technique.
(2)Zhongqiu Zhao's Ph.D. thesis P87:虽然此参数可能会给半监督学习带来可灵活机动的好处，但是同时它也增加了程序调试的难度。
(3)Fei Wang's Ph.D. thesis P13:图上半监督学习算法大都需要用高斯函数(式(1-6))计算数据之间的相似度，并且该函数中的自由参数\sigma是需要由用户指定的，这给这类算法在实际中的应用带来了很大的麻烦。