Analysis and Design of Optimization Algorithms via Integral Quadratic Constraints
summary
Claims that optimization algorithms map to a linear dynamical plant plus a nonlinear gradient block and that stability/rate can be certified by searching for Lyapunov functions via integral quadratic constraints leading to small semidefinite programs. Implements an off-by-one IQC to certify Nesterov‑style accelerated rates (within a constant) by solving tiny LMIs; heavy‑ball shows a surprising limit — a simple 1D counterexample with condition number ~16 produces a limit cycle so it fails certification. Also runs grid synthesis (Julia) to produce noise‑robust accelerated updates.
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chapters (19)
- 0:00Introduction
- 0:26Controls and optimization
- 2:20Controls for optimization
- 3:59First order methods
- 7:20Acceleration methods
- 10:20Nesterov's method
- 13:03Control theory framework
- 17:08Modeling algorithms as systems
- 22:47Analyzing convergence
- 24:49Linear matrix inequalities
- 29:40General convex functions
- 34:53Integral quadratic constraints
- 38:55Sufficient conditions
- 41:51Sector inequality proof
- 44:18Method comparison
- 49:28Off-by-one IQCs
- 55:40Heavy ball instability
- 58:57Synthesis and future work
- 1:02:53Q&A session
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