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==HalfKA==
In subsequent Stockfish versions the network architecture was further improved by [[Tomasz Sobczyk]] et al.. The '''HalfKA''' architecture uses 12x64x64 = 45056 inputs for each of the 12 piece types times 64 squares for each of the 64 own king squares, times two, for both the side to move and other side perspective, further using the [[Vertical Flipping|vertical flip]] instead of the HalfKP rotate.
'''HalfKv2''' of Stockfish '''14''' saves some space considering the king square redundancy using 11x64x64 = 45056 inputs per side, mapped to a 2x520 linear feature transformer, <ref>[https://github.aom/official-stockfish/Stockfish/commit/e8d64af1230fdac65bb0da246df3e7abe82e0838 New NNUE architecture and net · official-stockfish/Stockfish@e8d64af · GitHub]</ref> <ref>[https://github.com/official-stockfish/Stockfish/pull/3474 Update default net to nn-8a08400ed089.nnue by Sopel97 · Pull Request #3474 · official-stockfish/Stockfish · GitHub]</ref> <ref>[https://github.com/glinscott/nnue-pytorch/blob/master/docs/nnue.md#halfkav2-feature-set HalfKAv2 feature set | nnue-pytorch/nnue.md at master · glinscott/nnue-pytorch · GitHub]</ref>, further feeding 8x2 outputs of this feature transformer directly to the output for better learning of unbalanced material configurations <ref>[https://github.com/glinscott/nnue-pytorch/blob/master/docs/nnue.md#a-part-of-the-feature-transformer-directly-forwarded-to-the-output A part of the feature transformer directly forwarded to the output | nnue-pytorch/nnue.md at master · glinscott/nnue-pytorch · GitHub]</ref>. Another improvement was using eight 512x2->16->32->1 output sub-networks discriminated by (piece_count-1) div 4 in the 0 to 7 range
<ref>[https://github.com/glinscott/nnue-pytorch/blob/master/docs/nnue.md#multiple-psqt-outputs-and-multiple-subnetworks Multiple PSQT outputs and multiple subnetworks | nnue-pytorch/nnue.md at master · glinscott/nnue-pytorch · GitHub]</ref>.
