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4.2 UCI + WB Engine Settings

-fUCI or -firstIsUCI true/false
-sUCI or -secondIsUCI true/false
Indicates if the mentioned engine executable file is an UCI engine, and should be run with the aid of the Polyglot adapter rather than directly. Xboard will then pass the other UCI options and engine name to Polyglot on its command line, according to the option adapterCommand.
Options similar to fUCI and sUCI, except that they use the indicated engine with the protocol adapter specified in the ‘uxiAdapter’ option. This can then be configured for running an UCCI or USI adapter, as the need arises.
-adapterCommand string
The string conatins the command that should be issued by XBoard to start an engine that is accompanied by the fUCI option. Any identifier following a percent sign in the command (e.g. %fcp) will be considered the name of an XBoard option, and be replaced by the value of that option at the time the engine is started. For starting the second engine, any leading "f" or "first" in the option name will first be replaced by "s" or "second", before finding its value. Default: 'polyglot -noini -ec "%fcp" -ed "%fd"'
-uxiAdapter string
Similar to adapterCommand, but used for engines accompanied by the fUCCI or fUSI option, so you can configure XBoard to be ready to handle more than one flavor of non-native protocols. Default: ""
-polyglotDir filename
Gives the name of the directory in which the Polyglot adapter for UCI engines resides. Default: "".
-usePolyglotBook true/false
Specifies if the Polyglot book should be used as GUI book.
-polyglotBook filename
Gives the filename of the opening book. The book is only used when the usePolyglotBook option is set to true, and the option firstHasOwnBookUCI or secondHasOwnBookUCI applying to the engine is set to false. The engine will be kept in force mode as long as the current position is in book, and XBoard will select the book moves for it. Default: "".
-fNoOwnBookUCI or -firstXBook or -firstHasOwnBookUCI true/false
-sNoOwnBookUCI or -secondXBook or -secondHasOwnBookUCI true/false
Indicates if the mentioned engine has its own opening book it should play from, rather than using the external book through XBoard. Default: depends on setting of the option discourageOwnBooks.
-discourageOwnBooks true/false
When set, newly loaded engines will be assumed to use the GUI book, unless they explicitly specify differently. Otherwise they will be assumed to not use the GUI book, unless the specify differently (e.g. with firstXBook). Default: false.
-bookDepth n
Limits the use of the GUI book to the first n moves of each side. Default: 12.
-bookVariation n
A value n from 0 to 100 tunes the choice of moves from the GUI books from totally random to best-only. Default: 50
When this volatile option is specified, the probing algorithm of the GUI book is altered to always select the move that is most under-represented based on its performance. When all moves are played in approximately the right proportion, a book miss will be reported, to give the engine opportunity to explore a new move. In addition score of the moves will be kept track of during the session in a book buffer. By playing an match in this mode, a book will be built from scratch. The only output are the saved games, which can be converted to an actual book later, with the ‘Save Games as Book’ command. This command can also be used to pre-fill the book buffer before adding new games based on the probing algorithm.
-fn string or -firstPgnName string
-sn string or -secondPgnName string
Indicates the name that should be used for the engine in PGN tags of engine-engine games. Intended to allow you to install verions of the same engine with different settings, and still distinguish them. Default: "".
-defaultHashSize n
Sets the size of the hash table to n MegaBytes. Together with the EGTB cache size this number is also used to calculate the memory setting of XBoard/WinBoard engines, for those that support the memory feature of the XBoard/WinBoard protocol. Default: 64.
-defaultCacheSizeEGTB n
Sets the size of the EGTB cache to n MegaBytes. Together with the hash-table size this number is also used to calculate the memory setting of XBoard/WinBoard engines, for those that support the memory feature of the XBoard/WinBoard protocol. Default: 4.
-defaultPathEGTB filename
Gives the name of the directory where the end-game tablebases are installed, for UCI engines. Default: "/usr/local/share/egtb".
-egtFormats string
Specifies which end-game tables are installed on the computer, and where. The argument is a comma-separated list of format specifications, each specification consisting of a format name, a colon, and a directory path name, e.g. "nalimov:/usr/local/share/egtb". If the name part matches that of a format that the engine requests through a feature command, xboard will relay the path name for this format to the engine through an egtpath command. One egtpath command for each matching format will be sent. Popular formats are "nalimov" DTM tablebases and "scorpio" bitbases. Default: "".
This option lets you customize the drop-down list of chess engine names that appears in the ‘Load Engine’ and ‘Match Options’ dialog. It consists of a list of strings, one per line. When an engine is loaded, the corresponding line is prefixed with "-fcp ", and processed like it appeared on the command line. That means that apart from the engine command, it can contain any list of XBoard options you want to use with this engine. (Commonly used options here are -fd, -firstXBook, -fUCI, -variant.)

The value of this option is gradually built as you load new engines through the ‘Load Engine’ menu dialog, with ‘Add to list’ ticked. To change it, edit your settings file with a plain text editor.