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RbfNN_CCU

Adapting certified certain uncertainty (CCU) robust model from Towards neural networks that provably know when they don't know

A natural extension which makes use of a mathematical machinery similar to Gaussian Mixture Models (GMM) is the radial basis function (RBF) neural networks where we will build from Alessio Russo

Goal is to integrate RBF layer with Robust model sharing RBF and GMM computation for efficiency. The CCU is able to reduce confidence far from the expected input distance from a Multi-layer-perceptron (MLP). We will illustrate this using SKlearns two moons data set for a non-linear decision boundary. MLP Vs. CCU Where we can see on the left the base MLP has high confidence in the feature space far from the decision boundary.

RBFNNs also mirror the high confidence far from the decision boundary, but use their radial basis functions to determine how to define decision boundaries. RBFNN_conf

The RBFNNs do not learn to map the density in the same way as the GMMs. They place their centers based on where optimizes learning decision boundaries. The following plot will show the centers of the RBF and GMMs as well as their learned kernels.

RBF_Vs_GMM_Centers

To illustrate this further I will show the learning process of the RBF kernels and GMM likelihood both with 10 centers on our two moons data set.

RBF Learning Kernels

RBF Learning Kernels

GMM Learning in EM

GMM Learning

Where from the above we can see that the RBF kernels do not have the stability seen from the EM algorithm. This comes the two competing optimizations.

Fixing the centers,based on the GMM centers, and learning the RBF looks like the below. RBF_GMM_Centers

Implement beyond spherical variance for clusters and modify distance metrics.

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Adapting robust model from https://github.com/AlexMeinke/certified-certain-uncertainty with an RBF which shares centers with GMMs.

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