Released in early 2020, Stockfish 11 was the strongest chess engine in the world — and it was the last version to use a hand-written evaluation function. Every judgement it makes about a position comes from rules that human programmers wrote down explicitly: this is what a passed pawn is worth, this is how much king safety matters, this is the penalty for a bad bishop.
A few months later Stockfish 12 shipped with NNUE, and the hand-written evaluation was gone. Stockfish 11 is therefore a snapshot of the end of an era — the peak of an approach that had dominated computer chess for thirty years, taken as far as it could go.
It is genuinely interesting to watch it play against a modern version. The positions where it goes wrong are rarely tactical; it calculates superbly. They are positions where the modern engine simply understands something that nobody managed to write down as a rule.
What makes it distinctive
- ▸Classical hand-written evaluation, no neural network anywhere
- ▸Strength floor of 1350 rather than the 1320 of modern versions
- ▸The clearest way to see what NNUE actually changed