Unrolled Algorithms

Interactive Explorer 2

Explore key concepts interactively

Parameters

Quick Check

Key concept question for section 2?

Option A

Option B

Option C

Common Mistake: Common Mistake in Section 2

Mistake:

Overlooking a critical implementation detail.

Correction:

Always verify results against known benchmarks and theoretical predictions.

Key Term 2

Core concept from section 2 of chapter 43.

Definition:

Plug-and-Play (PnP)

PnP replaces the proximal operator with a pre-trained denoiser:

x(k+1)=Dσ(x(k)+AH(yAx(k))/L)\mathbf{x}^{(k+1)} = D_\sigma(\mathbf{x}^{(k)} + \mathbf{A}^H(\mathbf{y}-\mathbf{A}\mathbf{x}^{(k)})/L)

No training on paired data needed — only a pre-trained denoiser.

Definition:

Diffusion Posterior Sampling (DPS)

DPS uses a pre-trained diffusion model to sample from the posterior:

p(xy)p(yx)p(x)p(\mathbf{x}|\mathbf{y}) \propto p(\mathbf{y}|\mathbf{x}) p(\mathbf{x})

The diffusion model provides p(x)p(\mathbf{x}); the likelihood p(yx)=N(Ax,σ2I)p(\mathbf{y}|\mathbf{x}) = \mathcal{N}(\mathbf{A}\mathbf{x}, \sigma^2\mathbf{I}) guides sampling.