In memory of Professor Dyson, also see the paper Equivalence in Deep Neural Networks via Conjugate Matrix Ensembles
Preamble
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| Dyson 2007 (Wikipedia) |
Freeman Dyson was a polymath scientist: theoretical physicist, mathematician and visionary thinker among others. In this post, we will briefly summarise his contribution to deep learning, i.e., deep neural networks. Obscure usage of his circular ensembles as a simulation tool in conjunction with the concept of ergodicity explained why deep learning systems learn in such high accuracy.
A simulation tool for deep learning: Circular (Random Matrix) Ensembles
Circular ensembles [1,2,3] developed by Dyson in 1962 for explaining quantum statistical mechanics systems as a modification of basic random matrix theory. Circular ensembles can be used in simulating deep learning architectures [4]. Basically, his three ensembles can be used to generate a "trained deep neural network". It is shown by myself with colleagues from Hamburg and Mallorca that using Dyson's ensembles generated networks, deeper they are so-called spectral ergodicity goes down [4], this is recently proved on real networks as well [5].
How to generate a simulated trained deep neural network in Python
Using Bristol python package [6] one could generate a set of weight matrices corresponding to each layer connections, i.e., weight matrices. A simple example, using Circular Unitary Ensemble (CUE), let's say we have 4 hidden layers of 64, 64, 128, 256 units. This would generate learned weight matrices of sizes 64x64, 64x128 and 128x256, One possible trained network weights can be generated: Note that we make non-square ones by simple multiplying by its transpose.
from bristol.ensembles import circular
ce = circular()
seed_v = 997123
W1 = ce.gue(64, set_seed=True, seed=seed_v)
W2 = ce.gue(128, set_seed=True, seed=seed_v)
W3 = ce.gue(256, set_seed=True, seed=seed_v)
These are complex matrices, one could take the arguments or use them as it is if only eigenvalues are needed. An example of a trained network generation can be found in Zenedo. One can use any one of the circular ensembles.
Conclusion
Dyson's contributions are so bright that even his mathematical tools appear in modern deep learning research. He will be remembered many generations to come as a bright scientist and a polymath.
References
[1] Freeman Dyson, Journal of Mathematical Physics 3, 1199 (1962) [
link]
[2] Michael Berry, New Journal of Physics 15 (2013) 013026 [
link]
[3] Mehmet Süzen (2017), Summary Notebook on Circular ensembles [
link]
[4] Spectral Ergodicity in Deep Learning Architectures via Surrogate Random Matrices,
Mehmet Süzen, Cornelius Weber, Joan J. Cerdà, arXiv:1704.08693 [
link]
[5] Periodic Spectral Ergodicity: A Complexity Measure for Deep Neural Networks and Neural Architecture Search,
Mehmet Süzen, Cornelius Weber, Joan J. Cerdà, arXiv:1911.07831 [
link]
[6] Bristol Python package [
link]
