Style-Neutralized Pattern Classification Based on Adversarially Trained Upgraded U-Net

Traditional machine learning approaches usually hold the assumption that data for model training and in real applications are created following the identical and independent distribution (i.i.d.). However, several relevant research topics have demonstrated that such condition may not always describe the real scenarios. One particular case is that the patterns are equipped with diverse and changeable style information. In this paper, a novel classification framework named Style Neutralization Generative Adversarial Classifier (SN-GAC), based on an upgraded U-Net architecture, and trained adversarially with the Generative Adversarial Network (GAN) framework, is introduced to accomplish the classification in such disparate and inconsistent data information case. The generative model in SN-GAC neutralizes style information from the original style-discriminative patterns (style-source) by building the mapping function from them to their style-free counterparts (corresponding standard examples, standard-target). A well-learned generator in the SN-GAC framework is capable of producing the targeted style-neutralized data (generated-target), satisfying the i.i.d. condition. Additionally, SN-GAC is trained adversarially, where an independent discriminator is used to surveil and supervise the training progress of the above-mentioned generator by distinguishing between the real and the generated. Simultaneously, an auxiliary classifier is also embedded in the discriminator to assign the correct class label of both the real and generated data. This process proves effective to aid the generator to produce high-quality human-readable style-neutralized patterns. It will then be further fine-tuned for the sake of promoting the final classification performance. Extensive experiments have adequately demonstrated the effectiveness of the proposed SN-GAC framework: it outperforms several relevant state-of-the-art baselines on two empirical data sets in the non-i.i.d. data classification task.