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Man Pages

Manual Reference Pages  -  POLYGLOT (6)

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PolyGlot - Winboard protocol to UCI protocol adapter
- book engine for Polyglot books
- a collection of utilities for creating and analyzing opening books
- a utility for analyzing epd files
- a perft counter



polyglot [configfile] [-noini] [-ec engine] [-ed enginedirectory] [-en enginename] [-log true/false] [-lf logfile] [-pg <name>=<value>]* [-uci <name>=<value>]*

polyglot make-book [-pgn inputfile] [-bin outputfile] [-max-ply ply] [-min-game games] [-min-score score] [-only-white] [-only-black] [-uniform]

polyglot merge-book -in1 inputfile1 -in2 inputfile2 [-out outputfile]

polyglot info-book [-bin inputfile] [-exact]

polyglot dump-book [-bin inputfile] -color color [-out outputfile]

polyglot [configfile] epd-test [engineoptions] [-epd inputfile] [-min-depth depth] [-max-depth depth] [-max-time time] [-depth-delta delta]

polyglot perft [-fen fen] [-max-depth depth]


PolyGlot as adapter and book engine

PolyGlot is a UCI adapter. It connects a GUI interface (such as XBoard, Winboard, Arena or Chessbase) to a UCI chess engine.

By specifying an opening book (in PolyGlot book format) chess engines can transparently use such books.

PolyGlot understands the two main GUI protocols: UCI and xboard. Normally the protocol will be auto detected but this can be overridden in the configuration file.

In xboard mode PolyGlot fully translates between the xboard and UCI protocols. In addition it tries to solve known problems with other adapters. For instance, it detects and reports draws by fifty-move rule, repetition, etc ... It also supports Chess960.

When in UCI mode PolyGlot mostly passes commands from the GUI to the engine and vice versa, except that it will play book moves on behalf of the engine when the occasion arises.

The engine options are exported as UCI options in UCI mode and as feature option= commands in xboard mode. The latter form an extension of the xboard protocol as defined by H.G. Muller.

Options which normally appear in the [PolyGlot] section of the config file (see below) are exported as options with their name prefixed by Polyglot. This makes it easy to filter them in the GUI.

NOTE: Not all options are exported, only those that make sense in the given mode.

Book making utilities

PolyGlot supports the PolyGlot opening book format. This is the defacto standard non-proprietary opening book format. It is fully documented here

Roughly speaking a PolyGlot opening book is a collection of triples (position, move, weight). A position is represented by a 64-bit Zobrist hash key. The weight is proportional to the probability the move should be played.

Other opening book formats such as ChessBase’s .ctg format and Arena’s .abk format are undocumented and proprietary. They can only be used by their own GUIs.

PolyGlot can compile a pgn file into a binary PolyGlot book and furthermore it can merge two such binary books into a third one.

PolyGlot can also extract some useful information from PolyGlot books. The utility dump-book dumps the lines in a book for a given color. By definition a line is a sequence of moves (from the starting position) in which the given color makes only book moves and the other color makes arbitrary moves (i.e. not necessarily book moves).

Since a PolyGlot book is built up from positions and not lines there may be (and there usually are) many positions in the book that are not on a line as defined in the previous paragraph. It is convenient to call such positions isolated positions. The utility info-book counts such isolated positions.

Some of the isolated positions are provably unreachable and they could in principle be deleted from the book. For example if a book contains only the move e4 in the starting position but also the position after d4 d5 then this last position is provably unreachable since it requires white to make a non-book move when a book move is available. Such situations arise frequently from the priority rules in merging books.

Unfortunately not all isolated positions are provably unreachable and it is difficult to identify the latter. If invoked with -exact the utility info-book will attempt to count the isolated positions which require a player to make a non-book move when a book move is available. Due to the possibility of transpositions this is not a fool proof method.

Epd test mode

In epd test mode, PolyGlot will search positions in an epd file and record the number of times the right best move was found. The arguments specify when to stop the search in any given position.

Perft counts

A perft count is the number of legal move sequence in a given position up to a given depth. PolyGlot can perform such perft counts. It is however much slower than other more dedicated programs.


When PolyGlot is invoked as an adapter of in epd-test mode it gets its options from a config file and then from the command line. The default config file is polyglot.ini but an alternative one may be optionally included as first argument. The config file format is described below.

The following engine options may be specified on the command line.
-noini Do not use a config file, even if one was specified on the command line.
-pg The argument is a string of the form <name>=<value>. This option will set the Polyglot option <name> to <value>.
-uci The argument is a string of the form <name>=<value>. This option will set the engine option <name> to <value>.
-ec This is an alias for -pg EngineCommand=<value>
-ed This is an alias for -pg EngineDir=<value>
-en This is an alias for -pg EngineName=<value>
-log (default: false) This is an alias for -pg Log=<value>
-lf (default: ‘‘polyglot.log’’) This is an alias for -pg LogFile=<value>.
-wb (default: ‘‘true’’) This is an alias for -pg OnlyWbOptions=<value>.
When invoked as

polyglot make-book

PolyGlot supports the following options
-pgn (default: ‘‘book.pgn’’) Input file in pgn format.
-bin (default: ‘‘book.bin’’) Output file in PolyGlot format.
-max-ply (default: 1024) Specifies the maximum ply-depth of lines included in the book.
-min-game (default: 3) Specifies the minimum number of games that have to contain this move for it to be included in the book.
-min-score (default: 0.0) Specifies the minimum score (or weight) this move should have received for it to be included in the book. The score is 2*(wins)+(draws), globally scaled to fit into 16 bits.
-only-white Include only moves for white in the book.
-only-black Include only moves for black in the book.
-uniform Set all weights to 1. In other words, all moves will be selected with equal probability.
When invoked as

polyglot merge-book

PolyGlot supports the following options
-in1 First input file (in PolyGlot book format).
-in2 Second input file (in PolyGlot book format).
-out (default: out.bin) Output file (in PolyGlot book format).
Input files are not symmetrical, in1 has priority over in2. In other words when a position occurs both in in1 and in2 only the moves and weights from in1 will be retained in out.

When invoked as

polyglot dump-book

PolyGlot supports the following options
-bin (default: book.bin) Input file in PolyGlot book format.
-color The color for whom to generate the lines.
-out (default: book_<color>.txt) The name of the output file.
When invoked as

polyglot info-book

PolyGlot supports the following options
-bin (default: book.bin) Input file in PolyGlot book format.
-exact Attempt to count the provably unreachable positions among the isolated ones. Note that this takes a very long time.
When invoked as

polyglot epd-test

(possibly with a config file as first argument) PolyGlot supports besides the generic options described above the following additional options.
-max-depth (default: 63) Unconditionally stop the search when this depth has been reached.
-max-time (default: 5.0) Unconditionally stop the seach after this amount of time.
-depth-delta (default: 3) Stop the search if the solution as been found and the best move has been constant for this many depths, on condition that the mininal depth and minimal time have been reached.
-min-depth (default: 8) Minimal search depth when the search is stopped using -depth-delta.
-min-time (default: 1.0) Minimal search time when the search is stopped using -depth-delta.
When invoked as

polyglot perft

PolyGlot supports the following options
-fen (default: starting position) Fen at which to start searching.
-max-depth (default: 1) Maximum depth to search.


There should be a different config file for each engine.

The config file is in the traditional INI format.

    option = value
    option = value

The characters # and ; serve as comment characters.

Initial and final white space is stripped from option names and values. If you need to use characters which have a special meaning to PolyGlot (these are ’;#[]=\’) you should quote them by preceding them with ’\’. Quoting other characters in this way has no effect. In particular the use of ’\’ as a path separator in windows should normally not affected.

[PolyGlot] section

This section is used by PolyGlot only. The engine is unaware of these options. The list of available options is detailed below.
EngineName (default: UCI name) This is the name that will appear in the GUI. It is cosmetic only. You can use different names for tweaked versions of the same engine.
EngineDir (default: ‘‘.’’) Full path of the directory where the engine is installed. You can use . (without the quotes) if you know that PolyGlot will be launched in the engine directory or the engine is in the path and does not need any data file.
EngineCommand Put here the name of the engine executable file. You can also add command-line arguments. Path searching is used and the current directory will be EngineDir. On Linux the EngineCommand is passed to wordexp so that shell quoting rules and expansions are applied. On Windows the EngineCommand is simply passed to CreateProcess which does its own shell like processing.
SettingsDir (default: $HOME/.polyglot on Linux; ‘‘.\_PG’’ on Windows) The directory where ini files are stored for engines that are started with -noini. Such ini files may be created by pushing the Save button in the Engine settings dialog in WB/XB 4.4.0 and higher. As a special exception (for WB/XB 4.4.0 compatibility) this directory is also used in case PolyGlot is started with config files named polyglot_1st.ini or polyglot_2nd.ini.
Log (default: false) Whether PolyGlot should log all transactions with the interface and the engine. This should be necessary only to locate problems.
LogFile (default: polyglot.log) The name of the log file. Note that it is put where PolyGlot was launched from, not into the engine directory.

WARNING: Log files are not cleared between sessions, and can become very large. It is safe to remove them though.

Resign (default: false) Set this to true if you want PolyGlot to resign on behalf of the engine.

NOTE: Some engines display buggy scores from time to time although the best move is correct. Use this option only if you know what you are doing (e.g. you always check the final position of games).

ResignMoves (default: 3) Number of consecutive moves with resign score (see below) before PolyGlot resigns for the engine. Positions with only one legal move are ignored.
ResignScore (default: 600) This is the score in centipawns that will trigger resign counting.
ShowPonder (default: true) Show search information during engine pondering. Turning this off might be better for interactive use in some interfaces.
ScoreWhite (default: true) Report score from white’s point of view in xboard mode.
KibitzMove (default: false) Whether to kibitz when playing a move.
KibitzPV (default: false) Whether to kibitz when the PV is changed (new iteration or new best move).
KibitzCommand (default: ‘‘tellall’’) xboard command to use for kibitzing, normally tellall for kibitzing or tellothers for whispering.
KibitzDelay (default: 5) How many seconds to wait before starting kibitzing. This has an effect only if KibitzPV is selected, move kibitzes are always sent regardless of the delay.
KibitzInterval (default: 0) This is another form of throttling. PolyGlot will usually wait this many seconds before doing the next kibitz.
UCI (default: false) If true PolyGlot will not understand xboard commands.
MateScore (default: 10000) Mate score reported to GUI when in xboard mode.
Book (default: false) Indicates whether a PolyGlot book should be used. This has no effect on the engine own book (which can be controlled with the UCI option OwnBook in the [Engine] section). In particular, it is possible to use both a PolyGlot book and an engine book. In that case, the engine book will be used whenever PolyGlot is out of book. Remember that PolyGlot is unaware of whether the engine is itself using a book or not.
BookFile (default: book.bin) The name of the (binary) book file. Note that PolyGlot will look for it in the directory it was launched from, not in the engine directory. Of course, full path can be used in which case the current directory does not matter.
BookRandom (default: true) Select moves according to their weights in the book. If false the move with the highest weight is selected.
BookLearn (default: false) This is a noop.
BookDepth (default: 256) Stop using the book after this number of moves.
BookTreshold (default: 5) Do not play moves with a weight (probability) lower than this (in per mil).
UseNice (default: false) Run the engine at nice level 5, or NiceValue if it set. On some operating systems it may be necessary to run the engine at lower priority for it to be responsive to commands from PolyGlot while searching.
NiceValue (default: 5) Nice levels go from -20 to 20 with 20 being the lowest priority. On Unix only root can set negative nice levels. On Windows the standard Win32 priority levels are mapped in a sensible way to Unix nice levels.
Affinity (default: -1) This a bit vector in which each bit represents the processors that a process is allowed to run on. This option works only on Windows.
STFudge (default: 20) PolyGlot will translate st x as go movetime 1000*x-STFudge. The rationale is that in the UCI specification the argument of movetime is defined as the exact search time whereas the argument of the st command is only an upperbound.
OnlyWbOptions (default: true) If true then PolyGlot restricts the options it sends to those that are potentially useful for WinBoard.

Work arounds

Work arounds are identical to options except that they should be used only when necessary. Their purpose is to try to hide problems with various software (not just engines).

IMPORTANT: Any of these work arounds might be removed in future versions of PolyGlot. You are strongly recommended to contact the author of faulty software and truly fix the problem.

PolyGlot supports the following work arounds:
UCIVersion (default: 2) The default value of 2 corresponds to UCI+. Use 1 to select plain UCI for engines that have problems with UCI+.
CanPonder (default: false) PolyGlot now conforms to the documented UCI behaviour: the engine will be allowed to ponder only if it (the engine) declares the Ponder UCI option. However some engines which can actually ponder do not declare the option. This work around lets PolyGlot know that they can ponder.
SyncStop (default: false) When a ponder miss occurs, Polyglot interrupts the engine and IMMEDIATELY launches a new search. While there should be no problem with this, some engines seem confused and corrupt their search board. SyncStop forces PolyGlot to wait for the (now useless) ponder search to finish before launching the new search.
PromoteWorkAround (default: false) Some engines do not specify a promotion piece, e.g. they send e7e8 instead of the correct e7e8q. This work around enables the incorrect form (and of course promotes into a queen).
RepeatPV (default: true) When true, PolyGlot repeats the last pv string (which also contains score,depth and time usage) it got from the engine. Some engines however do not send a new pv string just before sending the move. In that case the output of PolyGlot would be inconsistent. When RepeatPV is false PolyGlot does not repeat the last pv string. Due to the way kibitzing is implemented, KibitzMove is disabled in that case.

[Engine] section

This section contains engine UCI options. PolyGlot does not understand them, but sends the information to the engine at startup (converted to UCI form). You can add any UCI option that makes sense to the engine (not just the common options about hash-table size and tablebases).

NOTE: use INI syntax, not UCI. For example OwnBook = true is correct. It will be replaced by PolyGlot with setoption name OwnBook value true at engine startup.

Standard UCI options are


Hidden options like Ponder or UCI_xxx are automatic and should not be put in an INI file.

The other options are engine-specific. Check their name using a UCI GUI or launch the engine in a console and type uci.


Running the UCI engine fruit under xboard 4.3.15 and later (this invokes PolyGlot internally).

    xboard -fcp fruit -fUCI

An explicit command line for using the UCI engine fruit with logging enabled (this works also with older versions of xboard).

    xboard -fcp "polyglot -noini -log true -ec fruit"

The equivalent config file would be:

    EngineCommand = fruit
    Log = true

Compile games.pgn into a book book.bin retaining all lines of at most 30 plies.

    polyglot make-book -pgn games.pgn -bin book.bin -max-ply 30

Merge books w1.bin and w2.bin into a book w.bin.

    polyglot merge-book -in1 w1.bin -in2 w2.bin -out w.bin

Inspect lines for white in w.bin

    polyglot dump-book -bin w.bin -color white -out w_white.txt

Test epd file test.epd with a (maximum) search time of 7 minutes per position

    polyglot epd-test -epd test.epd -max-time 420


PolyGlot always returns 0 on exit.


Main author: Fabien Letouzey<fabien_letouzey(at)>

Native Windows port: Huang Chen<> (Morning Yellow)

Various enhancements: Fonzy Bleumers<match(at)>

UCI port and implementation of new WB protocol: Michel Van den Bergh <michel.vandenbergh(at)>


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POLYGLOT (6) 2011-06-01

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