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Poster
Maximum Class Separation as Inductive Bias in One Matrix
Tejaswi Kasarla · Gertjan Burghouts · Max van Spengler · Elise van der Pol · Rita Cucchiara · Pascal Mettes

Tue Nov 29 02:00 PM -- 04:00 PM (PST) @ Hall J #112
in Poster Session 2 »

Maximizing the separation between classes constitutes a well-known inductive bias in machine learning and a pillar of many traditional algorithms. By default, deep networks are not equipped with this inductive bias and therefore many alternative solutions have been proposed through differential optimization. Current approaches tend to optimize classification and separation jointly: aligning inputs with class vectors and separating class vectors angularly. This paper proposes a simple alternative: encoding maximum separation as an inductive bias in the network by adding one fixed matrix multiplication before computing the softmax activations. The main observation behind our approach is that separation does not require optimization but can be solved in closed-form prior to training and plugged into a network. We outline a recursive approach to obtain the matrix consisting of maximally separable vectors for any number of classes, which can be added with negligible engineering effort and computational overhead. Despite its simple nature, this one matrix multiplication provides real impact. We show that our proposal directly boosts classification, long-tailed recognition, out-of-distribution detection, and open-set recognition, from CIFAR to ImageNet. We find empirically that maximum separation works best as a fixed bias; making the matrix learnable adds nothing to the performance. The closed-form implementation and code to reproduce the experiments are available on github.

Keywords: maximum separation · inductive bias
[ Paper]  [ Poster]  [ OpenReview] 

Author Information

Tejaswi Kasarla (University of Amsterdam)
Gertjan Burghouts (TNO - Intelligent Imaging)
Max van Spengler (University of Amsterdam)
Elise van der Pol (Microsoft Research)
Rita Cucchiara (Univ. Modena Reg.)
Pascal Mettes (University of Amsterdam)

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