Research Article

Chess Position Evaluation Using Radial Basis Function Neural Networks

Table 1

Stockfish evaluation feature components.

FeatureDescriptionComponents

MaterialWeighted values and bonuses related to pieces and pawns, and their position on the boardNonpawn material, PSQT mg, PSQT eg, piece value mg, piece value eg
MobilityValues and bonuses related to the available squares pieces can reachMobility, mobility area, mobility mg, mobility eg
KingBonuses and penalties related to king placement such as position relative to friendly and enemy pieces, pawn shelters, pawn storms, weak squares, attacks, and available checksKing pawn distance, blockers for king, knight defender, king attacks, king attackers count, king attackers weight, pawnless flank, flank attack, flank defence, storm square, shelter storm, shelter strength, endgame shelter, strength square, weak squares, weak bonus, king danger, check, safe check, unsafe checks, king mg, king eg
SpaceWeighted bonus for safe squares on own side of the boardSpace, space area
Initiative (winnable)Bonus or penalty for initiative aspects such as passed pawns, piece infiltration, and flank majoritiesInitiative, initiative total eg, initiative total mg
ImbalanceWeighted values and bonus or penalty for material differences such as the bishop pairImbalance, imbalance total, bishop pair
PiecesValues and bonuses or penalties related to specific patterns of piece placement on the boardOutpost, outpost square, reachable outpost, outpost total, rook on file, long diagonal bishop, rook on queen file, weak queen, trapped rook, rook on king ring, queen infiltration, bishop pawns, bishop x-ray pawns, minor behind pawn, king protector, pieces mg, pieces eg
PawnsValues and bonuses or penalties related to specific patterns of pawn placement on the boardSupported, phalanx, connected, connected bonus, opposed, isolated, doubled, doubled isolated, backward, blocked, weak unopposed pawn, weak lever, pawns mg, pawns eg
Passed pawnsValues and bonuses or penalties related to passed pawns placement on the boardCandidate passed, passed rank, passed file, passed leverable, passed block, king proximity, passed mg, passed eg
AttackValues related to attacked squares and piecesPawn attack, knight attack, bishop x-ray attack, rook x-ray attack, queen attack, queen diagonal attack, king attack, pinned, attack
ThreatsValues related to threatened and supported pieces and pawnsHanging, restricted, weak enemies, safe pawn, threat safe pawn, pawn push threat, minor threat, rook threat, king threat, weak queen protection, slider on queen, knight on queen, threats mg, threats eg