“…A mainstream methodology is distribution alignment, which is mainly based on Maximum Mean Discrepancy (MMD) [1,2,23,25,30] or adversarial methods [9,11,26,45,46]. Besides, some works further make improvement by pseudo-labeling [33], co-training [45], entropy regularization [36], and evolutionary-based architecture design [34]. Recently, increasing researchers focus on more realistic scenarios: considering user privacy, [22,24] investigate the scenario where only source domain models instead of data available while training.…”