Modular addition without black-boxes: Compressing explanations of MLPs that compute numerical integration

Fuente: arXiv
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Main Authors: Yip, Chun Hei, Agrawal, Rajashree, Chan, Lawrence, Gross, Jason
Format: Preprint
Published: 2024
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author Yip, Chun Hei
Agrawal, Rajashree
Chan, Lawrence
Gross, Jason
author_facet Yip, Chun Hei
Agrawal, Rajashree
Chan, Lawrence
Gross, Jason
contents The goal of mechanistic interpretability is discovering simpler, low-rank algorithms implemented by models. While we can compress activations into features, compressing nonlinear feature-maps -- like MLP layers -- is an open problem. In this work, we present the first case study in rigorously compressing nonlinear feature-maps, which are the leading asymptotic bottleneck to compressing small transformer models. We work in the classic setting of the modular addition models, and target a non-vacuous bound on the behaviour of the ReLU MLP in time linear in the parameter-count of the circuit. To study the ReLU MLP analytically, we use the infinite-width lens, which turns post-activation matrix multiplications into approximate integrals. We discover a novel interpretation of} the MLP layer in one-layer transformers implementing the ``pizza'' algorithm: the MLP can be understood as evaluating a quadrature scheme, where each neuron computes the area of a rectangle under the curve of a trigonometric integral identity. Our code is available at https://tinyurl.com/mod-add-integration.
format Preprint
id arxiv_https___arxiv_org_abs_2412_03773
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Modular addition without black-boxes: Compressing explanations of MLPs that compute numerical integration
Yip, Chun Hei
Agrawal, Rajashree
Chan, Lawrence
Gross, Jason
Machine Learning
Artificial Intelligence
The goal of mechanistic interpretability is discovering simpler, low-rank algorithms implemented by models. While we can compress activations into features, compressing nonlinear feature-maps -- like MLP layers -- is an open problem. In this work, we present the first case study in rigorously compressing nonlinear feature-maps, which are the leading asymptotic bottleneck to compressing small transformer models. We work in the classic setting of the modular addition models, and target a non-vacuous bound on the behaviour of the ReLU MLP in time linear in the parameter-count of the circuit. To study the ReLU MLP analytically, we use the infinite-width lens, which turns post-activation matrix multiplications into approximate integrals. We discover a novel interpretation of} the MLP layer in one-layer transformers implementing the ``pizza'' algorithm: the MLP can be understood as evaluating a quadrature scheme, where each neuron computes the area of a rectangle under the curve of a trigonometric integral identity. Our code is available at https://tinyurl.com/mod-add-integration.
title Modular addition without black-boxes: Compressing explanations of MLPs that compute numerical integration
topic Machine Learning
Artificial Intelligence
url https://arxiv.org/abs/2412.03773