Stockfish 12 Released, 130 Elo Points Stronger

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Version 12 of the popular open-source chess engine Stockfish was released on Thursday. It is a major update that includes an efficiently updatable neural network and is significantly stronger than earlier versions.

According to the official Stockfish blog, version 12 of Stockfish plays significantly stronger than any of its predecessors: "In a match against Stockfish 11, Stockfish 12 will typically win at least 10 times more game pairs than it loses."

The rating difference compared to Stockfish 11 is estimated to be about 130 Elo points. This became clear from internal progression tests during development and was recently confirmed In's computer chess environment where Stockfish+NNUE and Leela Chess Zero performed quite comparably.

Stockfish 12 progress rate
Image: Gary Linscott/Github.

The jump in strength is mainly the result of the introduction of NNUE, which stands for "efficiently updatable neural network." At the same time, Stockfish remains a CPU-only engine.

Stockfish 12 combines the brute-force computing approach of traditional Stockfish with the advanced evaluation capabilities of neural network chess engines such as AlphaZero and Leela Chess Zero.

In the new version, two evaluation functions are available. Besides the classical evaluation function, there is now the NNUE evaluation which is computed with a neural network based on basic inputs. The network is optimized and trained on the evaluations of millions of positions.

Wotawa, 1937
German Chess Magazine #1979

This study is known to be a tough nut to crack for chess engines. On this author's computer, Stockfish 11 took 4 minutes and 54 seconds to show the winning move as its first choice. Stockfish 12 took only 38 seconds.

One early user wrote on Reddit: "From personal experience, Stockfish 12’s positional understanding is really unlike anything before it. Even Leela on extremely powerful hardware can seem blind to Stockfish 12’s search. Pretty much every major blindspot, like pawn structure weaknesses, seems gone in this new evaluation."

Stockfish 12 is available for download here with the neural network already embedded and ready to go. expects to soon have Stockfish 12 available in our "max analysis" feature.

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