Optimizer-Induced Mode Connectivity: From AdamW to Muon
- URL: http://arxiv.org/abs/2605.09991v1
- Date: Mon, 11 May 2026 05:07:36 GMT
- Title: Optimizer-Induced Mode Connectivity: From AdamW to Muon
- Abstract summary: We show that solutions from a single -- AdamW, Muon, or others in the Lion-$mathcalK$ family -- form a connected set at sufficiently large width.<n>We then characterize how-induced regions interact: at large width two different regions can be disjoint or overlap depending on regularization.
- Score: 50.258866851760416
- License: http://creativecommons.org/licenses/by/4.0/
- Abstract: Mode connectivity has been widely studied, yet the role of the optimizer remains underexplored. We revisit it through optimizer-induced implicit regularization, asking how connectivity behaves when restricted to solutions constrained by a given optimizer. For two-layer ReLU networks, we show that solutions from a single optimizer -- AdamW, Muon, or others in the Lion-$\mathcal{K}$ family -- form a connected set at sufficiently large width, a result not implied by prior work. We then characterize how optimizer-induced regions interact: at large width two different regions can be disjoint or overlap depending on regularization, while in our small-width example AdamW and Muon converge to disconnected zero-loss components separated by a provable loss barrier. Empirically, in GPT-2 pretraining, we observe same-optimizer paths preserve each model's spectrum while cross-optimizer paths traverse a smooth transition. Our results reveal optimizer-dependent structure beyond classical mode connectivity literature.
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