We propose a novel method that tackles the problem of unsupervised domain adaptation for semantic segmentation by maximizing the cosine similarity between the source and the target domain at the feature level. A segmentation network mainly consists of two parts, a feature extractor and a classification head. We expect that if we can make the two domains have small domain gap at the feature level, they would also have small domain discrepancy at the classification head. Our method computes a cosine similarity matrix between the source feature map and the target feature map, then we maximize the elements exceeding a threshold to guide the target features to have high similarity with the most similar source feature. Moreover, we use a class-wise source feature dictionary which stores the latest features of the source domain to prevent the unmatching problem when computing the cosine similarity matrix and be able to compare a target feature with various source features from various images. Through extensive experiments, we verify that our method gains performance on two unsupervised domain adaptation tasks (GTA5$\to$ Cityscaspes and SYNTHIA$\to$ Cityscapes).

本文提出一种新的方法，通过在特征层面上最大化源域和目标域之间的余弦相似度来解决语义分割的无监督域适应问题。通过广泛的实验，我们验证了我们的方法在两个无监督域适应任务（GTA5 $ 	o $ Cityscapes和SYNTHIA $ 	o $ Cityscapes）上获得了性能提升。

最大化空间特征的余弦相似度，用于语义分割的无监督域自适应