L1,L2正则化cookbook L1正则化为啥更容易产生稀疏解 感觉这里解释的更清晰 https://www.zhihu.com/question/37096933/answer/475278057 或者 https://blog.csdn.net/b876144622/article/details/81276818?utm_medium=distribute.pc_aggpage_search_result.none-task-blog-2~all~first_rank_v2~rank_v25-1-81276818.nonecase