Proxy metric
Beginner
A quick score that stands in for the real result, like judging a cake by its smell before tasting it.
Novice
A quick estimate optimized in place of the real result, such as estimated wire length instead of the wire length measured after the slow routing step.
Expert
A proxy is only useful while it ranks options in the same order as the real metric. That agreement often weakens among the best options, so a better proxy score can fail to give a better chip.
Explained in AI in EDA (Extras).
See also: Reinforcement learning (RL), HPWL (half-perimeter wirelength).