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Data-Free/Data-Sparse Softmax Parameter Estimation With Structured Class Geometries

delete2018-09-01
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Nisar Ahmed *
DOI:10.1109/LSP.2018.2860238delete
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Abstract

Abstract

En 中文
This note considers softmax parameter estimation when little/no labeled training data is available, but a priori information about the relative geometry of class label log-odds boundaries is available. It is shown that data-free softmax model synthesis corresponds to solving a linear system of parameter equations, wherein desired dominant class log-odds boundaries are encoded via convex polytopes that decompose the input feature space. When solvable, the linear equations yield closed-form softmax parameter solution families using class boundary polytope specifications only. This allows softmax parameter learning to be implemented without expensive brute force data sampling and numerical optimization. The linear equations can also be adapted to constrained maximum likelihood estimation in data-sparse settings. Since solutions may also fail to exist for the linear parameter equations derived from certain polytope specifications, it is thus also shown that there exist probabilistic classification problems over m convexly separable classes for which the log-odds boundaries cannot be learned using an m-class softmax model.
Keywords:
Classification algorithms
estimation
hybrid probabilistic models
neural networks
pattern recognition
probabilistic logic
supervised learning

Journal

IEEE Signal Processing Magazine cover
IEEE Signal Processing Magazine
IF:
9.6
Papers:
1.1W
Citations:
1.7W

Organization

University of Colorado System cover
University of Colorado System
Scholars:
6.3W
Papers: 5.5W
Citations: 1.8K