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Poster

Improved Finite-Particle Convergence Rates for Stein Variational Gradient Descent

Krishna Balasubramanian · Sayan Banerjee · PROMIT GHOSAL

Hall 3 + Hall 2B #404
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Sat 26 Apr midnight PDT — 2:30 a.m. PDT
 
Oral presentation: Oral Session 5D
Fri 25 Apr 7:30 p.m. PDT — 9 p.m. PDT

Abstract: We provide finite-particle convergence rates for the Stein Variational Gradient Descent (SVGD) algorithm in the Kernelized Stein Discrepancy (\KSD) and Wasserstein-2 metrics. Our key insight is that the time derivative of the relative entropy between the joint density of N particle locations and the N-fold product target measure, starting from a regular initial distribution, splits into a dominant 'negative part' proportional to N times the expected \KSD2 and a smaller 'positive part'. This observation leads to \KSD rates of order 1/N, in both continuous and discrete time, providing a near optimal (in the sense of matching the corresponding i.i.d. rates) double exponential improvement over the recent result by~\cite{shi2024finite}. Under mild assumptions on the kernel and potential, these bounds also grow polynomially in the dimension d. By adding a bilinear component to the kernel, the above approach is used to further obtain Wasserstein-2 convergence in continuous time. For the case of `bilinear + Mat\'ern' kernels, we derive Wasserstein-2 rates that exhibit a curse-of-dimensionality similar to the i.i.d. setting. We also obtain marginal convergence and long-time propagation of chaos results for the time-averaged particle laws.

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