Wednesday, April 21 2021
17:30 - 18:30

IMSc Webinar

Recent Developments in the Mathematics of Neural Nets

Anirbit Mukherjee

University of Pennsylvania
Meeting ID: 917 8237 5389; password: Turing

A profound mathematical mystery of our times is to be able to
explain the phenomenon of training neural nets i.e ``deep-learning”.
The dramatic progress of this approach in the last decade has gotten
us the closest we have ever been to achieving "artificial
intelligence". But trying to reason about these successes - for even
the simplest of nets - immediately lands us into a plethora of
extremely challenging mathematical questions, typically about
discrete stochastic processes. In this talk we will describe the
various themes of our work in provable deep-learning.

We will start with a brief introduction to neural nets and then see
glimpses of our initial work on understanding neural functions, loss
functions for autoencoders and algorithms for exact neural training.
Next, we will explain our recent result about how under mild
distributional conditions we can construct an iterative algorithm
which can be guaranteed to train a ReLU gate in the realizable
setting in linear time while also keeping track of mini-batching -
and its provable graceful degradation of performance under a
data-poisoning attack. We will show via experiments the intriguing
property that our algorithm very closely mimics the behaviour of
Stochastic Gradient Descent (S.G.D.), for which similar convergence
guarantees are still unknown.

Lastly, we will review this very new concept of "local elasticity"
of a learning process and demonstrate how it appears to reveal
certain universal phase transitions during neural training. Then we
will introduce a mathematical model which reproduces some of these
key properties in a semi-analytic way. We will end by delineating
various exciting future research programs in this theme of
macroscopic phenomenology with neural nets.

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