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/ stockfish-mac Public

# User Guide

## Playing a game

Stockfish for Mac is a 2-player game. You can move pieces by clicking the source and destination squares, or by dragging and dropping. The app checks the game state after every turn and declares a win or draw when it happens.

Under the View menu, you can flip the board or go full screen.

## Navigating a game

Under the Move menu, you will find shortcuts to browse through a game. You can use the arrow keys to go back and forward, or use the ⌘ Cmd key with an arrow key to jump to the beginning or end. If you make a mistake when inputing a move, you can also use Edit > Undo and Edit > Redo.

## Analyzing a game

Under the Engine menu, you can choose "Start Infinite Analysis" to start analysis. Alternatively, you can click the "Go" button in the bottom right pane. To stop analysis, just click the Stop button or use Engine > Stop Infinite Analysis. The keyboard shortcut to start or stop analysis is ⌘ Cmd + I.

## Interpreting the analysis

• Engine name: This is the name of the engine.
• Score: This is a number that shows who's winning. A zero score means the game is even (draw). A positive score means white is winning. Negative means black is winning. The score is measured in pawn units, so +1 means white is winning by 1 pawn. If there is a forced checkmate, the score is displayed with a hashtag (#) and the number of moves until checkmate.
• Depth: How deep the engine has searched in the search tree. In other words, it's how far the engine has looked ahead. This is usually displayed in the form ##/##. The first number is the depth in half-moves. A half-move is when one side moves a piece. The second number is the selective depth, because for some lines, the engine will search deeper. More depth is better.
• Current move: Sometimes the engine will display the current move it is analyzing. This might look something like `1. e4 (1/20)`. This just lets you know what the engine is analyzing right now, and the order in which it is analyzing moves. In the example above, there are 20 legal moves, and the engine is currently analyzing e4, which it orders as the most promising move.
• Speed: This is measured in nodes (positions) per second. This depends on the speed of your processor. More is better.
• MultiPV: Shows the number of lines (ranked from best to worst) the engine will display. Increasing the number of displayed lines slows down analysis. The default is 1.
• Principal variation: In bold text at the bottom, the engine displays the principal variation, or the best continuation of chess moves from the current position. If you use MultiPV, additional lines are displayed below the best line.

## MultiPV

Sometimes you want to know the 2nd or 3rd best move in addition to the best move. Enable more lines of analysis in the Engine menu. Choose Increase Variations or Decrease Variations to increase or decrease the number of lines of analysis. You cannot go lower than 1 line.

## FEN strings

Stockfish for Mac supports copying and pasting FEN strings. A FEN string is a single line of text that contains the entire state of a chess position, including the locations of the pieces, castling rights, the en passant square, and the side to move. As such, they’re very useful for sharing specific chess positions with others. To copy the FEN string for the currently displayed position to the clipboard, use Edit > Copy FEN or ⌥⌘C. The FEN string will be copied to the clipboard. If you have a FEN string in your clipboard that you would like to paste into Stockfish, use Edit > Paste FEN or ⌥⌘V. Important note: pasting a FEN string will overwrite whatever game is currently being played.

## PGN files

Stockfish for Mac supports opening, browsing, and saving multi-game PGN files. Note that it does not support variations or commentary, and these will be stripped out of PGN files that you open with Stockfish for Mac. You can open a PGN file just as you would open any other file on your Mac. You can step through the game and analyze the game as described above. If the PGN file contains multiple games, the list of games is displayed in a sidebar on the left, and you can select any game to view it. You can also save PGN files using File > Save.

## Preferences

Access preferences using Stockfish > Preferences.

• Threads: The number of threads the engine will use. For best performance, set this to be the number of physical cores in your CPU.
• Hash size: The amount of memory the engine should use during analysis. For best performance, set this number to be half the size of the RAM in your computer.
• Contempt: If you use high contempt, the engine will play riskier moves. Negative contempt means the engine will seek a draw. Default is zero (neutral).
• Skill Level: Adjust the skill level of the engine. Maximum (strongest) is 20. Worst is zero. Default is 20.
• Syzygy Path: The Stockfish engine supports Syzygy endgame tablebases. If you have them downloaded, you can choose the folder where they are stored for the engine to use them.