Doctoral Thesis Oral Defense - Asher James Trockman

— 2:00pm

Location:
In Person and Virtual - ET - Blelloch-Skees Conference Room, Gates Hillman 8115 and Zoom

Speaker:
ASHER JAMES TROCKMAN, Ph.D. Candidate, Computer Science Department, Carnegie Mellon University
https://ashertrockman.com/

Mimetic Initialization for Deep Neural Networks

While neural network weights are typically initialized randomly from univariate distributions, pre-trained weights often have visually-discernible multivariate structure. We propose a technique called "mimetic initialization" that aims to replicate such structures when initializing convolutional networks (CNNs), Transformers, and State Space Models (SSMs). For CNNs, we handcraft a class of multivariate Gaussian distributions to initialize filters for depthwise convolutional layers; for Transformers, we initialize the query and key weights for self-attention layers such that their product approximates the identity; and for SSMs, we initialize layers to approximate simple linear attention. Mimetic initialization substantially reduces training time and increases final accuracy on various common small-scale benchmarks.  

Our technique enables us to almost close the gap between untrained and pre-trained Vision Transformers on small datasets like CIFAR-10, achieving up to a 6% gain in accuracy through initialization alone. For convolutional networks like ConvMixer and ConvNeXt, we observe improvements in accuracy and reductions in training time, even when convolutional filters are frozen (untrained) after initialization. For SSMs, mimetic initialization substantially improves generalization abilities on synthetic language tasks like copying and associative recall. Overall, our findings suggest that the benefits of pre-training can be separated into two components: serving as a good initialization and storing transferable knowledge, with the former being simple enough to (at least partially) capture by hand in closed-form.  

Thesis Committee

Zico Kolter (Chair)
Albert Gu
Aditi Raghunathan
Sébastien Bubeck (OpenAI)

In Person and Zoom Participation.  See announcement.

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