- // Check extension (~2 Elo)
- else if ( givesCheck
- && (pos.is_discovery_check_on_king(~us, move) || pos.see_ge(move)))
- extension = 1;
-
- // Passed pawn extension
- else if ( move == ss->killers[0]
- && pos.advanced_pawn_push(move)
- && pos.pawn_passed(us, to_sq(move)))
- extension = 1;
-
- // Last captures extension
- else if ( PieceValue[EG][pos.captured_piece()] > PawnValueEg
- && pos.non_pawn_material() <= 2 * RookValueMg)
- extension = 1;
-
- // Castling extension
- if (type_of(move) == CASTLING)
- extension = 1;
-
- // Late irreversible move extension
- if ( move == ttMove
- && pos.rule50_count() > 80
- && (captureOrPromotion || type_of(movedPiece) == PAWN))
- extension = 2;
-