Preprint Open access
AREX: Affine-Residual Exponential Integrator for Few-Step Sampling in Flow Matching
We introduce AREX, a training-free sampler for pretrained flow matching models that uses the target mean and covariance to capture an analytically tractable part of the sampling dynamics. We show that the velocity field of the moment-matched Gaussian target is the $L^2$-optimal affine approximation to the marginal velo …