FlexConv: Continuous Kernel Convolutions with Differentiable Kernel Sizes

Our convolutional kernel is an implicit neural representation, attenuated by a learnable Gaussian mask.


When designing Convolutional Neural Networks (CNNs), one must select the size of the convolutional kernels before training. Recent works show CNNs benefit from different kernel sizes at different layers, but exploring all possible combinations is unfeasible in practice. A more efficient approach is to learn the kernel size during training. However, existing works that learn the kernel size have a limited bandwidth. These approaches scale kernels by dilation, and thus the detail they can describe is limited. In this work, we propose FlexConv, a novel convolutional operation with which high bandwidth convolutional kernels of learnable kernel size can be learned at a fixed parameter cost. FlexNets model long-term dependencies without the use of pooling, achieve state-of-the-art performance on several sequential datasets, outperform recent works with learned kernel sizes, and are competitive with much deeper ResNets on image benchmark datasets. Additionally, FlexNets can be deployed at higher resolutions than those seen during training. To avoid aliasing, we propose a novel kernel parameterization with which the frequency of the kernels can be analytically controlled. Our novel kernel parameterization shows higher descriptive power and faster convergence speed than existing parameterizations. This leads to important improvements in classification accuracy.

Proceedings of the 10th International Conference on Learning Representations (ICLR 2022)
Robert-Jan Bruintjes
Robert-Jan Bruintjes
PhD candidate

Interested in integrating prior knowledge into Convolutional Neural Networks to benefit data efficiency and/or robustness.

Jan van Gemert
Jan van Gemert
Associate Professor

Head of the CV Lab.