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arXiv 1809.06124cs.LGstat.ML
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加权SVM的跨度误差界及其在超参数选择中的应用

Span error bound for weighted SVM with applications in hyperparameter selection

Aristotle University of Thessaloniki(塞萨洛尼基亚里士多德大学)

Ioannis Sarafis, Christos Diou, Anastasios Delopoulos

摘要:

加权支持向量机(或模糊支持向量机)是最广泛使用的支持向量机的变种,其有效性的使用实例的权重。正确选择实例权重可以提高泛化性能。在这项工作中,我们扩展了跨度误差界理论加权SVM,我们引入了有效的超参数选择方法的加权SVM算法。所提出的工作的意义是,使应用的跨度界和跨度规则与加权支持向量机。跨度界限是可以使用单个训练的SVM模型计算的留一法误差的上限。这很重要,因为留一误差是测试误差的几乎无偏估计量。类似地,跨度规则给出了留一法误差的实际值。因此,可以应用跨度界和跨度规则作为计算轻量的替代方案的留一法超参数选择过程。本文的主要理论贡献是:(a)证明了加权支持向量机中支持向量跨度存在的充要条件;(b)证明了跨度界和跨度规则在加权支持向量机中的推广。我们实验评估的跨度界和跨度规则的超参数选择,我们比较它们与其他方法,适用于加权SVM:$K$折交叉验证和$ξ-α$界。在14个基准数据集和具有重要性分数的数据集上的实验表明:(a)加权SVM的跨度存在条件几乎总是满足的;(b)跨度规则是加权SVM超参数选择的最有效方法;(c)跨度规则在均方误差意义下是测试误差的最佳预测器;以及(d)跨度规则是有效的,并且对于某些问题,它可以比$K$ -折叠交叉验证更快地计算。

英文摘要:

Weighted SVM (or fuzzy SVM) is the most widely used SVM variant owning its effectiveness to the use of instance weights. Proper selection of the instance weights can lead to increased generalization performance. In this work, we extend the span error bound theory to weighted SVM and we introduce effective hyperparameter selection methods for the weighted SVM algorithm. The significance of the presented work is that enables the application of span bound and span-rule with weighted SVM. The span bound is an upper bound of the leave-one-out error that can be calculated using a single trained SVM model. This is important since leave-one-out error is an almost unbiased estimator of the test error. Similarly, the span-rule gives the actual value of the leave-one-out error. Thus, one can apply span bound and span-rule as computationally lightweight alternatives of leave-one-out procedure for hyperparameter selection. The main theoretical contributions are: (a) we prove the necessary and sufficient condition for the existence of the span of a support vector in weighted SVM; and (b) we prove the extension of span bound and span-rule to weighted SVM. We experimentally evaluate the span bound and the span-rule for hyperparameter selection and we compare them with other methods that are applicable to weighted SVM: the $K$-fold cross-validation and the $ξ-α$ bound. Experiments on 14 benchmark data sets and data sets with importance scores for the training instances show that: (a) the condition for the existence of span in weighted SVM is satisfied almost always; (b) the span-rule is the most effective method for weighted SVM hyperparameter selection; (c) the span-rule is the best predictor of the test error in the mean square error sense; and (d) the span-rule is efficient and, for certain problems, it can be calculated faster than $K$-fold cross-validation.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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