AdaShift: Learning Discriminative Self-Gated Neural Feature Activation With an Adaptive Shift Factor

Nonlinearities are decisive in neural representation learning. Traditional Activation (Act) functions impose fixed inductive biases on neural networks with oriented biological intuitions. Recent methods leverage self-gated curves to compensate for the rigid traditional Act paradigms in fitting flexibility. However, substantial improvements are still impeded by the norm-induced mismatched feature re-calibrations (see Section 1), i.e., the actual importance of a feature can be inconsistent with its explicit intensity such that violates the basic intention of a direct self-gated feature re-weighting. To address this problem, we propose to learn discriminative neural feature Act with a novel prototype, namely, AdaShift, which enhances typical self-gated Act by incorporating an adaptive shift factor into the re-weighting function of Act. AdaShift casts dynamic translations on the inputs of a re-weighting function by exploiting comprehensive feature-filter context cues of different ranges in a simple yet effective manner. We obtain the new intuitions of AdaShift by rethinking the feature-filter relationships from a common Softmax-based classification and by generalizing the new observations to a common learning layer that encodes features with updatable filters. Our practical AdaShifts, built upon the new Act prototype, demonstrate significant improvements to the popular/SOTA Act functions on different vision benchmarks. By simply replacing ReLU with AdaShifts, ResNets can match advanced Transformer counterparts (e.g., ResNet-50 vs. Swin-T) with lower cost and fewer parameters.