This is a 2D-native reading of the same DARTS mechanism as the 3D version: every edge in the cell's DAG is still a continuous softmax mixture over 4 candidate operations, still updated by gradient ascent on architecture weights α. Instead of parallel 3D tubes, each edge here is drawn as a flat arc between its two nodes (an "arc diagram" — arc height grows with how many nodes the edge skips) plus a small vertical composition bar at its midpoint whose colored segments are exactly the live softmax mixture. A second panel below the graph plots architecture entropy, estimated validation score and training loss as time series, so the whole search trajectory — not just a single frozen instant — is visible at once.
ō(x) = Σ_k softmax(α_k / τ) · o_k(x)
softmax(α_k/τ) = exp(α_k/τ) / Σ_j exp(α_j/τ)
∂(expected quality)/∂α_k = softmax_k · (q_k − Σ_j softmax_j·q_j)
α_k ← α_k + (ξ/τ) · ∂(expected quality)/∂α_k
- Architecture LR ξ — step size for the α update each iteration; higher means faster, noisier convergence toward the best-looking op per edge.
- Temperature τ — softens (high τ) or sharpens (low τ) the softmax mixture without touching α itself, exactly like annealing a Gumbel-softmax relaxation.
- Composition bar — the stacked colored segment per edge is the live softmax mixture over the 4 ops; it sharpens into one dominant color as α converges.
- Time-series panel — entropy (dashed), val. score (solid) and train loss (dotted) plotted against iteration count, so you can see the whole trajectory instead of one snapshot.
- Discretize — freezes the search and keeps only the argmax operation per edge, exactly as DARTS prunes its supernet down to a single derived child architecture.
This weight-sharing / continuous-relaxation approach (Liu, Simonyan & Yang, 2019) is what makes NAS tractable without training thousands of child networks from scratch — the whole supernet trains once, and the final architecture is read off its converged α values.