Editing 3045: AlphaMove

{{comic
| number    = 3045
| date      = January 31, 2025
| title     = AlphaMove
| image     = alphamove_2x.png
| imagesize = 500x526px
| noexpand  = true
| titletext = It struggles a little with complex positions, like when there are an even number of moves and it has to round down, but when run against itself it's capable of finding some novelties. At one point I saw six knights on the board at once; Stockfish rarely exceeds four.
}}

==Explanation==
{{incomplete|Created by THE SEVENTH KNIGHT, WAITING IN ANTICIPATION. Do NOT delete this tag too soon.}}
This comic shows a new {{w|chess engine}}, presumably created by [[Randall]], which takes a list of all legal moves (in {{w|Algebraic notation (chess)|algebraic notation}}) in alphabetical order and chooses the median.

A playable implementation of this game can be found here: [https://enn-nafnlaus.github.io/AlphaMove/alphamove.html AlphaMove].

Algebraic notation begins with a symbol for which piece is being moved, which is always the first letter of the piece name except for knights (N) and pawns (nothing). This is then followed by the square that the piece is being moved to. (Rc4 would indicate a move that moved a rook to c4.) Other symbols include a lowercase x before the destination, indicating that the move is a capture; a plus sign (+) after the destination, indicating that the move places the opposing king in check; and a hash sign (#) after the destination, indicating that the move places the opposing king in checkmate, thus winning the game. There is also O-O and O-O-O, which indicate that a player is castling kingside or queenside, respectively.

In practice, this algorithm runs into a few issues. As seen in the comic, the algorithm rarely moves bishops and rooks due to their relative lack of moves in the early game, and their tendency to inhabit the edges of any list when they do have sortable moves. Among basic moves, only pawns destined to move in the first two files of a board can ever sort higher than bishops, and nothing other than another rook can be closer to the far end than a rook. AlphaMove can never {{w|Castling|castle}} due to the notation for it (0-0 or 0-0-0) being the only one to start with a number, and thus (if ever possible) always being the first in the list. (It's also not possible to create a board state where it's the only legal move, both because the king or rook moving without castling is a legal move, and because castling cannot be done while in check.) The algorithm instead favors knight and king moves, with entries starting with the most alphabetically middling "K" and "N" list entries, and (to a lesser extent) pawns destined to move up the right side of the board, the "h"-file pawn generally having the greatest statistical chance. The shortcomings of AlphaMove are instantly apparent from looking at the game board presented in the comic; roughly ten moves into the game, White has lost three pawns, captured nothing, and advanced their king into the open rather than developing any pieces, while Black (presumably being played by a 'stronger' conventional chess engine) has taken control of the center with a knight and two pawns, developed a bishop, and advanced their queen to f2.

The ''actual'' middle of the list might vary away from the usual alphabetic median if the moves (and the pieces removed by the opponent) are heavily biased to a particular subset of player-pieces. It is conceivable that an opponent could identify the AlphaMove strategy as being used, and then use their foreknowledge of the algorithm's 'developing game' to strategically make (normally non-optimal?) moves designed explicitly to force the algorithm down their own choice of paths, such as targeting undefended rooks and queens (either capturing them with impunity, or just strategically restricting their movements by moving into contact with them in such a way as to normally be a suicidal sacrifice), in order to make certain other pieces take their own moves. Although, given the established failings of uncritically sticking to the algorithmic plan, it is probably ''vastly'' more effort to precisely engineer a given game-state than to merely play properly, and respond with half-decent responses to the overwhelmingly sub-optimal series of moves. For example, setting Stockfish (black) against AlphaMove (white) results in the following fifteen-move victory for black:
# f3 e5
# e4 Bc5
# d4 Bxd4
# f4 d5
# g4 Qh4+
# Ke2 Qf2+
# Kd3 dxe4+
# Kxe4 Nf6+
# Kd3 e4+
# Kc4 Be6+
# Kb5 a6+
# Ka5 Bc3+
# Ka4 b5+
# Ka3 Qc5+
# b4 Qxb4#
On the other hand, a person playing black who knew that white was using AlphaMove could win in seven moves (possibly fewer):
# f3 d5
# e4 d5xe4
# f4 e5
# g3 Bg4
# d4 Qxd4
# f5 e3
# f6 Qxd1#
However, chess tournaments do not award more points for quicker victories, and playing like this would be risky because if white initially uses AlphaMove and black goes for the seven-move checkmate, white could capture black's undefended bishop on move five, revealing the AlphaMove emulation to just be a rouse to get black to hang a bishop, then white would be in a winning position after 5. Qxg4 and could play smartly for the rest of the game and would likely win, so going for the fifteen-move mate would likely be safer.

Even if AlphaMove ever found one or more of its potential moves to be one that happens to result in checkmate, it has no reason to do anything other than choose its "mid-list move", as described, and the chances are high that such a mate would never be invoked. Along those lines, Qa4+ is a relatively safe move to create a short-term check, to put immediate pressure upon the black king, and potentially a longer term inconvenience with 'only' a predictable response<!-- b5 by black would create the possibility of a pawn+queen swap, or even just a queen loss, if not retreated from by white; c6, dNc6 *or* eNc6, instead, would also effectively neuter the queen (with any immediate attempt to press home the 'advantage' resulting in a probable whatever+queen swap); but doing Kf8 would just open up Qe8# as an option, under 'normal' playing conditions--> preventing it from developing into a mate. But it is not in the right list position to attempt, anyway, never mind whether it would then be correctly followed up.

This engine may be named for and inspired by the real chess engine, {{w|AlphaZero}}. Another real name, mentioned in the title text, is {{w|Stockfish (chess)|Stockfish}}, a widely used (and powerful) chess engine. 

On this board, Black can win the game instantly with ...Bb4{{w|Checkmate|#}}. Rather than do anything to defend against this, White just moves an unrelated piece, almost certainly losing right afterward. Randall has also chosen a setup where the King is placed in a position where it cannot make any legal moves, thus removing it from the list of pieces that can perform any moves. Almost certainly this was a choice, both to make the list without the Kings moves and also to make it pretty easy to see how one more move would mate the king.

The title of the comic is a play on words.  As the name of the chess engine, it refers to the strategy of choosing moves based on alphabetical ordering, while in popular usage, an "alpha move" is an action that would assert dominance over someone else.  This makes it an ironic name for the chess engine; rather than asserting dominance, it loses quickly.

The title text mentions games with "six knights", which implies that two pawns have been promoted to knights. Pawns can promote to bishop, knight, queen or rook, so the middle of this list is tied between knight or queen. It is rare that a pawn promotes to knights, when in most normal situations (not setup in a chess puzzle) a Queen would always be preferred. However, when AlphaMove plays itself,  the pawns move up opposing sides of the board and thus it is not unrealistic that a pawn would promote to a knight.

See also [[3036: Chess Zoo]], another recent comic about chess, which is a [[:Category:Chess|recurring theme]] on xkcd.

==Transcript==
:[A standard chessboard is shown with Black at the top. The boards "black squares" are light gray. Black (which is drawn as dark gray) has made moves resulting in Qf2, Nd4, e4, a5, Bc5, e5 and Ne7 while other black pieces are in starting positions. White has made moves resulting in c4, f4, h4, Kc3, Ne2 and three white pawns are removed from the board while other white pieces including a- and b-pawns are in starting positions. Two squares associated with white's move Ne2 are highlighted in yellow, it has moved there from its starting position g1.]

:[To the right of the chess board is a vertical list of possible moves listed in alphabetical order. The text is in light gray, except the move Ne2 in the middle which is black and highlighted in yellow. Two light gray double arrows with a line at the end of each arrow head goes from the top to just above the yellow move, and from just below this to the bottom. A short but thick black arrow points in between the space between the two gray arrows pointing at the yellow move.]
:<font color=”gray”>a3</font>
:<font color=”gray”>a4</font>
:<font color=”gray”>b3</font>
:<font color=”gray”>b4</font>
:<font color=”gray”>Bd2</font>
:<font color=”gray”>Bd3</font>
:<font color=”gray”>Be2</font>
:<font color=”gray”>Be3</font>
:<font color=”gray”>Bg2</font>
:<font color=”gray”>Bh3</font>
:<font color=”gray”>f5</font>
:<font color=”gray”>fxe5</font>
:<font color=”gray”>h5</font>
:<font color=”gray”>Na3</font>
:<font color=”gray”>Nd2</font>
: <span style="background:#fffca1">'''Ne2'''</span> 
:<font color=”gray”>Nf3</font>
:<font color=”gray”>Nh3</font>
:<font color=”gray”>Qa4+</font>
:<font color=”gray”>Qb3</font>
:<font color=”gray”>Qc2</font>
:<font color=”gray”>Qd2</font>
:<font color=”gray”>Qd3</font>
:<font color=”gray”>Qe1</font>
:<font color=”gray”>Qe2</font>
:<font color=”gray”>Qf3</font>
:<font color=”gray”>Qg4</font>
:<font color=”gray”>Qh5</font>
:<font color=”gray”>Qxd4</font>
:<font color=”gray”>Rh2</font>
:<font color=”gray”>Rh3</font>

:[Caption below the panel:]
:My new AlphaMove chess engine, which sorts the list of legal moves alphabetically and picks the middle one, was quickly defeated by stronger engines.

{{comic discussion}}

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[[Category:Chess]]