Sketching Algorithm Cuts Context Attribution Cost for Language Models
The matching lower bound means the algorithm is provably optimal in its oracle model, not just an empirical win. Interpretability researchers and teams auditing model behaviour on long prompts can reuse the backpropagation-sketching trick to cut attribution costs from linear in prompt length to near-constant in ε. Compared with prior forward-differentiation sketches needing Õ(log(n)/ε²) calls, the variance reduction is the concrete improvement to study.