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arXiv · 2604.14442

Hierarchical vs. Flat Iteration in Shared-Weight Transformers

Sang-Il Han
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Abstract

We present an empirical study of whether hierarchically structured, shared-weight recurrence can match the representational quality of independent-layer stacking in a Transformer-based language model. HRM-LM replaces L independent Transformer layers with a two-speed recurrent pair: a Fast module operating at every step for local refinement, and a Slow module operating every T steps for global compression. This recurrent hierarchy is unrolled for M = N x T steps with shared parameters. The central and most robust finding, supported by a parameter-matched Universal Transformer ablation (UniTF, 1.2B) across five independent runs, is a sharp empirical gap between the two approaches.

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Sang-Il Han. 2026-04-15. Hierarchical vs. Flat Iteration in Shared-Weight Transformers. https://arxiv.org/abs/2604.14442

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