Heuristic

A technique designed for solving a problem more quickly when classic methods are too slow, or for finding an approximate solution when classic methods fail.

How it works

A heuristic is a rule of thumb or educated guess that guides a search or decision process toward good solutions efficiently, without guaranteeing optimality. In pathfinding, A* uses a heuristic distance estimate to prioritise promising paths. In chess engines, evaluation functions are heuristics that score board positions without exhaustively searching all future moves. In prompt engineering, heuristics like 'tell the model to think step by step' are practical rules that reliably improve output quality.

Why it matters

Many real-world problems — logistics, game playing, scheduling, optimisation — have search spaces too large for exhaustive methods. Heuristics make these tractable. In AI research, heuristic design was central to classical AI and remains important in modern systems: the design choices in prompt templates, sampling strategies, and agent reasoning loops are all heuristics applied at the application layer of LLM-powered systems.