Score-Based Continuous Stochastic Differential Equations (Score SDE, pioneered by Yang Song) unifies discrete DDPMs and score-matching generative models into a continuous-time stochastic calculus framework; the forward noising process is parameterized as an Itô SDE:
dx=f(x,t)dt+g(t)dw (
f drift coefficient,
g diffusion coefficient,
w standard Brownian motion); via Anderson's Reverse-Time Theorem, the exact continuous
reverse-time generative process is proven to be another closed-form SDE:
dx=[f(x,t)−g(t)2∇xlnpt(x)]dt+g(t)dwˉ; neural generation simplifies to learning the score function
∇xlnpt(x) via score matching (
sθ(x,t)); furthermore, the deterministic Probability Flow ODE allows standard Runge-Kutta numerical solvers to generate samples in 10-20 steps.