DOTResize: Reducing LLM Width via Discrete Optimal Transport-based
  Neuron Merging
Authors: name: Neha Verma, name: Kenton Murray, name: Kevin Duh

Model compression offers a promising path to reducing the cost and
inaccessibility of large pre-trained models, without significantly compromising
their impressive performance. Large Transformer models, including large
language models (LLMs), often contain computational redundancy, which can serve
as a target for new model compression methods. In this work, we specifically
target neuron-level redundancies in model layers by combining groups of similar
neurons into fewer neurons. We frame this width reduction as a Discrete Optimal
Transport problem, and propose DOTResize, a novel Transformer compression
method that uses optimal transport theory to transform and compress model
weights. To ensure applicability within the Transformer architecture, we
motivate and incorporate entropic regularization and matrix factorization into
the transportation maps produced by our method. Unlike pruning-based approaches
which discard neurons based on importance measures, DOTResize re-projects the
entire neuron width, allowing the retention and redistribution of useful signal
across the reduced layer. Empirical results show that compared to simple or
state-of-the-art neuron width-pruning techniques, DOTResize can outperform
these methods across multiple LLM families and sizes, while achieving
measurable reductions in real-world computational cost.