残差加权算法
http://wenku.baidu.com/link?url=mBp6DkYB6CjpuLIUo7CxGxdbucVQ0HN72iPClY8JDfrYaFwVADDNcJiyeN3LRwUB2Olcj07iSIcyd_1SAWjelbXmfnNuVHxH39CtC3MdGzO
优化模型
http://wenku.baidu.com/link?url=dsI7bNllfpFCBLqi6rXzgr8bga5nmqbz5WqqtUOhyPZddYuXUXP9Ut42YsjfxJT3oWS5Cgn-8s7be-YXlZ9c5ZptoRuIZQkwmJVF71hCCxy