Domain Adaptive Learning Based on Sample-Dependent and Learnable Kernels

TL;DR

This paper introduces a novel domain adaptive learning method using sample-dependent, learnable kernels within RKHS, which improves performance by minimizing domain discrepancy and transforming data into an optimized feature space.

Contribution

It proposes a new positive definite quadratic kernel framework that is learnable and sample-dependent, applied to domain adaptive learning for better domain discrepancy minimization.

Findings

Outperforms several state-of-the-art DAL algorithms.

Learned kernels effectively reduce domain discrepancy.

Improves data transformation into optimized RKHS.

Abstract

Reproducing Kernel Hilbert Space (RKHS) is the common mathematical platform for various kernel methods in machine learning. The purpose of kernel learning is to learn an appropriate RKHS according to different machine learning scenarios and training samples. Because RKHS is uniquely generated by the kernel function, kernel learning can be regarded as kernel function learning. This paper proposes a Domain Adaptive Learning method based on Sample-Dependent and Learnable Kernels (SDLK-DAL). The first contribution of our work is to propose a sample-dependent and learnable Positive Definite Quadratic Kernel function (PDQK) framework. Unlike learning the exponential parameter of Gaussian kernel function or the coefficient of kernel combinations, the proposed PDQK is a positive definite quadratic function, in which the symmetric positive semi-definite matrix is the learnable part in machine learning applications. The second contribution lies on that we apply PDQK to Domain Adaptive Learning (DAL). Our approach learns the PDQK through minimizing the mean discrepancy between the data of source domain and target domain and then transforms the data into an optimized RKHS generated by PDQK. We conduct a series of experiments that the RKHS determined by PDQK replaces those in several state-of-the-art DAL algorithms, and our approach achieves better performance.