Exactly solvable theory shows when Muon beats Adam: steep spectra, hard targets

CatAstro_Piyush · x · 2026-11-04

Researchers built an exactly solvable theory comparing Muon and SignSGD, answering "when does Muon beat Adam?" The answer depends on the data: Muon wins on steep spectra (high decay exponent α) with hard targets (higher target exponent ζ), while SignSGD wins on flat spectra or easy targets. The phase diagram also reveals regimes where SignSGD leads early before Muon overtakes late, and regions where the two tie. This is the opening of a 10-tweet ML theory thread.

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