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<ref>[http://www.talkchess.com/forum3/viewtopic.php?f=7&t=74531&start=1 Re: NNUE accessible explanation] by [[Jonathan Rosenthal]], [[CCC]], July 23, 2020</ref>.
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 [[King|kings]], cross coupled with the side to move or not to move halves of the first hidden layer.
For each either black or white king placement, the 10 none king pieces on their particular squares are the boolean {0,1} inputs, along with a relict from Shogi piece drop (BONA_PIECE_ZERO),
64 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 = 10,503,144 weights.
As emphasized by [[Ronald de Man]] in a [[CCC]] forum discussion <ref>[http://www.talkchess.com/forum3/viewtopic.php?f=7&t=75506&start=7 Re: NNUE Question - King Placements] by [[Ronald de Man|syzygy]], [[CCC]], October 23, 2020</ref>,
the input weights are arranged in such a way, that [[Color Flipping|color flipped]] king-piece configurations in both halves share the same index.
However, and that seems also a relict from Shogi with its [https://en.wikipedia.org/wiki/Rotational_symmetry 180 degrees rotational] 9x9 board symmetry, instead of [[Vertical Flipping|vertical flipping]] (xor 56), [[Flipping Mirroring and Rotating#Rotationby180degrees|rotation]] was is applied (xor 63) <ref>[https://github.com/official-stockfish/Stockfish/issues/3021 NNUE eval rotate vs mirror · Issue #3021 · official-stockfish/Stockfish · GitHub] by [[Terje Kirstihagen]], August 17, 2020</ref>.
The efficiency of [[NNUE]] is due to [[Incremental Updates|incremental update]] of the input layer outputs in [[Make Move|make]] and [[Unmake Move|unmake move]],
