The input weights are arranged in such a way, that color flipped king-piece configurations in both halves share the same index.

The so called HalfKP structure consists of two halves covering input layer and first hidden layer, each half of the input layer associated to one of the two kings, cross coupled with the side to move or not to move halves of the first hidden layer.įor each either black or white king placement, the 10 none king pieces on their particular squares are the boolean inputs, along with a relict from Shogi piece drop (BONA_PIECE_ZERO),Ħ4 x (64 x 10 + 1) = 41,024 inputs for each half, which are multiplied by a 16-bit integer weight vector for 256 outputs per half, in total, 256 x 41,024 = 10,502,144 weights.Īs emphasized by Ronald de Man in a CCC forum discussion , The input layer is heavily overparametrized, feeding in the board representation for all king placements per side The neural network consists of four layers. On September 02, 2020, Stockfish 12 was released with a huge jump in playing strength due to the introduction of NNUE and further tuning. The training code still remained in Nodchip's repository for a while then replaced by PyTorch NNUE training. In August that playing code merged to the master branch and become an official part of the engine. In July 2020, the playing code of NNUE was put into the official Stockfish repository as a branch for further development and examination. In August 2020, Fishtest revealed Stockfish NNUE was stronger than the classical one at least 80 Elo. Despite the approximately halved search speed, Stockfish NNUE became stronger than its original. The computer chess community bursts out enthusiastically due to its rapidly raising playing strength with different networks trained using a mixture of supervised and reinforcement learning methods. In summer 2020, with more people involved in testing and training, Īfter support and announcements by Henk Drost in May 2020 Īnd subsequent enhancements, Stockfish NNUE was established and recognized.

In 2019, Nodchip incorporated NNUE into Stockfish 10 - as a proof of concept, and with the intention to give something back to the Stockfish community. YaneuraOu's author Motohiro Isozaki made an unbelievable prediction that NNUE can help to increase Stockfish strength by around 100 points, almost one year before revealing. Were previously successfully applied in Shogi evaluation functions embedded in a Stockfish based search, such as YaneuraOu ,Īnd Kristallweizen. A Stockfish branch by Hisayori Noda aka Nodchip, which uses Efficiently Updatable Neural Networks - stylized as ƎUИИ or reversed as NNUE - to replace its standard evaluation.

Stockfish 16 rating