Hyperspherical Classification with Dynamic Label-to-Prototype Assignment
Authors: Mohammad Saeed Ebrahimi Saadabadi, Ali Dabouei, Sahar Rahimi Malakshan, Nasser M. Nasrabadi

Aiming to enhance the utilization of metric space by the parametric softmax classifier recent studies suggest replacing it with a non-parametric alternative. Although a non-parametric classifier may provide better metric space utilization it introduces the challenge of capturing inter-class relationships. A shared characteristic among prior non-parametric classifiers is the static assignment of labels to prototypes during the training i.e. each prototype consistently represents a class throughout the training course. Orthogonal to previous works we present a simple yet effective method to optimize the category assigned to each prototype (label-to-prototype assignment) during the training. To this aim we formalize the problem as a two-step optimization objective over network parameters and label-to-prototype assignment mapping. We solve this optimization using a sequential combination of gradient descent and Bipartide matching. We demonstrate the benefits of the proposed approach by conducting experiments on balanced and long-tail classification problems using different backbone network architectures. In particular our method outperforms its competitors by 1.22% accuracy on CIFAR-100 and 2.15% on ImageNet-200 using a metric space dimension half of the size of its competitors. \href https://github.com/msed-Ebrahimi/DL2PA_CVPR24  Code