arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2006.07036stat.MLcs.LG
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谱混合核的近似推断

Approximate Inference for Spectral Mixture Kernel

KAIST(韩国科学技术院)

Yohan Jung, Kyungwoo Song, Jinkyoo Park

摘要:

光谱混合(SM)核是用于对任何平稳协方差函数建模的灵活核。虽然它在建模数据中是有用的,但SM内核的学习通常是困难的,因为优化SM内核的大量参数通常会引起过拟合,特别是当使用基于梯度的优化时。此外,还需要更长的培训时间。为了提高训练,我们提出了一个近似的贝叶斯推断的SM内核。具体地说,我们采用的光谱点的变分分布近似SM核与随机傅立叶特征。我们优化变分参数应用基于采样的变分推断推导出的证据下界(ELBO)估计构造的近似内核。为了改进推理,我们进一步提出了两个额外的策略:(1)谱点的采样策略,以可靠地估计ELBO估计量及其相关梯度,以及(2)近似自然梯度,以加速参数的收敛。提出的推理结合两种策略,加快了参数的收敛速度,并导致更好的最优参数。

英文摘要:

A spectral mixture (SM) kernel is a flexible kernel used to model any stationary covariance function. Although it is useful in modeling data, the learning of the SM kernel is generally difficult because optimizing a large number of parameters for the SM kernel typically induces an over-fitting, particularly when a gradient-based optimization is used. Also, a longer training time is required. To improve the training, we propose an approximate Bayesian inference for the SM kernel. Specifically, we employ the variational distribution of the spectral points to approximate SM kernel with a random Fourier feature. We optimize the variational parameters by applying a sampling-based variational inference to the derived evidence lower bound (ELBO) estimator constructed from the approximate kernel. To improve the inference, we further propose two additional strategies: (1) a sampling strategy of spectral points to estimate the ELBO estimator reliably and thus its associated gradient, and (2) an approximate natural gradient to accelerate the convergence of the parameters. The proposed inference combined with two strategies accelerates the convergence of the parameters and leads to better optimal parameters.

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