Dion: The distributed orthonormal update revolution is here
Kwangjun Ahn, Senior Researcher at Microsoft Research AI Frontiers, introduces Dion, a next-generation optimizer in the style of Muon that orthonormalizes only the top-r subspace via amortized power iteration. Dion retains Muonโs fast convergence while significantly reducing compute and communication, scaling efficiently with FSDP/TP for very large models.
Dion paper: https://arxiv.org/abs/2504.05295
Dion optimizer: https://github.com/microsoft/dion
This session aired on September 24, 2025, at Microsoft Research Forum, Season 2 Episode 1.
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