1 /* With friendly permission, to public this document,
2 * of Stefan-Mayer Kahlen
3 * For more information or newer versions of the
4 * UCI protcol please visit
5 * http://www.shredderchess.de/download.html
8 Description of the universal chess interface (UCI) April 2004
9 ================================================================
11 * The specification is independent of the operating system. For Windows,
12 the engine is a normal exe file, either a console or "real" windows application.
14 * all communication is done via standard input and output with text commands,
16 * The engine should boot and wait for input from the GUI,
17 the engine should wait for the "isready" or "setoption" command to set up its internal parameters
18 as the boot process should be as quick as possible.
20 * the engine must always be able to process input from stdin, even while thinking.
22 * all command strings the engine receives will end with '\n',
23 also all commands the GUI receives should end with '\n',
24 Note: '\n' can be 0x0c or 0x0a0c or any combination depending on your OS.
25 If you use Engine und GUI in the same OS this should be no problem if you cummunicate in text mode,
26 but be aware of this when for example running a Linux engine in a Windows GUI.
28 * The engine will always be in forced mode which means it should never start calculating
29 or pondering without receiving a "go" command first.
31 * Before the engine is asked to search on a position, there will always be a position command
32 to tell the engine about the current position.
34 * by default all the opening book handling is done by the GUI,
35 but there is an option for the engine to use its own book ("OwnBook" option, see below)
37 * if the engine or the GUI receives an unknown command or token it should just ignore it and try to
38 parse the rest of the string.
40 * if the engine receives a command which is not supposed to come, for example "stop" when the engine is
41 not calculating, it should also just ignore it.
47 The move format is in long algebraic notation.
48 A nullmove from the Engine to the GUI should be send as 0000.
49 Examples: e2e4, e7e5, e1g1 (white short castling), e7e8q (for promotion)
56 These are all the command the engine gets from the interface.
59 tell engine to use the uci (universal chess interface),
60 this will be send once as a first command after program boot
61 to tell the engine to switch to uci mode.
62 After receiving the uci command the engine must identify itself with the "id" command
63 and sent the "option" commands to tell the GUI which engine settings the engine supports if any.
64 After that the engine should sent "uciok" to acknowledge the uci mode.
65 If no uciok is sent within a certain time period, the engine task will be killed by the GUI.
68 switch the debug mode of the engine on and off.
69 In debug mode the engine should sent additional infos to the GUI, e.g. with the "info string" command,
70 to help debugging, e.g. the commands that the engine has received etc.
71 This mode should be switched off by default and this command can be sent
72 any time, also when the engine is thinking.
75 this is used to synchronize the engine with the GUI. When the GUI has sent a command or
76 multiple commands that can take some time to complete,
77 this command can be used to wait for the engine to be ready again or
78 to ping the engine to find out if it is still alive.
79 E.g. this should be sent after setting the path to the tablebases as this can take some time.
80 This command is also required once before the engine is asked to do any search
81 to wait for the engine to finish initializing.
82 This command must always be answered with "readyok" and can be sent also when the engine is calculating
83 in which case the engine should also immediately answer with "readyok" without stopping the search.
85 * setoption name <id> [value <x>]
86 this is sent to the engine when the user wants to change the internal parameters
87 of the engine. For the "button" type no value is needed.
88 One string will be sent for each parameter and this will only be sent when the engine is waiting.
89 The name of the option in <id> should not be case sensitive and can inludes spaces like also the value.
90 The substrings "value" and "name" should be avoided in <id> and <x> to allow unambiguous parsing,
91 for example do not use <name> = "draw value".
92 Here are some strings for the example below:
93 "setoption name Nullmove value true\n"
94 "setoption name Selectivity value 3\n"
95 "setoption name Style value Risky\n"
96 "setoption name Clear Hash\n"
97 "setoption name NalimovPath value c:\chess\tb\4;c:\chess\tb\5\n"
100 this is the command to try to register an engine or to tell the engine that registration
101 will be done later. This command should always be sent if the engine has send "registration error"
103 The following tokens are allowed:
105 the user doesn't want to register the engine now.
107 the engine should be registered with the name <x>
109 the engine should be registered with the code <y>
112 "register name Stefan MK code 4359874324"
115 this is sent to the engine when the next search (started with "position" and "go") will be from
116 a different game. This can be a new game the engine should play or a new game it should analyse but
117 also the next position from a testsuite with positions only.
118 If the GUI hasn't sent a "ucinewgame" before the first "position" command, the engine shouldn't
119 expect any further ucinewgame commands as the GUI is probably not supporting the ucinewgame command.
120 So the engine should not rely on this command even though all new GUIs should support it.
121 As the engine's reaction to "ucinewgame" can take some time the GUI should always send "isready"
122 after "ucinewgame" to wait for the engine to finish its operation.
124 * position [fen <fenstring> | startpos ] moves <move1> .... <movei>
125 set up the position described in fenstring on the internal board and
126 play the moves on the internal chess board.
127 if the game was played from the start position the string "startpos" will be sent
128 Note: no "new" command is needed. However, if this position is from a different game than
129 the last position sent to the engine, the GUI should have sent a "ucinewgame" inbetween.
132 start calculating on the current position set up with the "position" command.
133 There are a number of commands that can follow this command, all will be sent in the same string.
134 If one command is not send its value should be interpreted as it would not influence the search.
135 * searchmoves <move1> .... <movei>
136 restrict search to this moves only
137 Example: After "position startpos" and "go infinite searchmoves e2e4 d2d4"
138 the engine should only search the two moves e2e4 and d2d4 in the initial position.
140 start searching in pondering mode.
141 Do not exit the search in ponder mode, even if it's mate!
142 This means that the last move sent in in the position string is the ponder move.
143 The engine can do what it wants to do, but after a "ponderhit" command
144 it should execute the suggested move to ponder on. This means that the ponder move sent by
145 the GUI can be interpreted as a recommendation about which move to ponder. However, if the
146 engine decides to ponder on a different move, it should not display any mainlines as they are
147 likely to be misinterpreted by the GUI because the GUI expects the engine to ponder
148 on the suggested move.
150 white has x msec left on the clock
152 black has x msec left on the clock
154 white increment per move in mseconds if x > 0
156 black increment per move in mseconds if x > 0
158 there are x moves to the next time control,
159 this will only be sent if x > 0,
160 if you don't get this and get the wtime and btime it's sudden death
166 search for a mate in x moves
168 search exactly x mseconds
170 search until the "stop" command. Do not exit the search without being told so in this mode!
173 stop calculating as soon as possible,
174 don't forget the "bestmove" and possibly the "ponder" token when finishing the search
177 the user has played the expected move. This will be sent if the engine was told to ponder on the same move
178 the user has played. The engine should continue searching but switch from pondering to normal search.
181 quit the program as soon as possible
189 this must be sent after receiving the "uci" command to identify the engine,
190 e.g. "id name Shredder X.Y\n"
192 this must be sent after receiving the "uci" command to identify the engine,
193 e.g. "id author Stefan MK\n"
196 Must be sent after the id and optional options to tell the GUI that the engine
197 has sent all infos and is ready in uci mode.
200 This must be sent when the engine has received an "isready" command and has
201 processed all input and is ready to accept new commands now.
202 It is usually sent after a command that can take some time to be able to wait for the engine,
203 but it can be used anytime, even when the engine is searching,
204 and must always be answered with "isready".
206 * bestmove <move1> [ ponder <move2> ]
207 the engine has stopped searching and found the move <move> best in this position.
208 the engine can send the move it likes to ponder on. The engine must not start pondering automatically.
209 this command must always be sent if the engine stops searching, also in pondering mode if there is a
210 "stop" command, so for every "go" command a "bestmove" command is needed!
211 Directly before that the engine should send a final "info" command with the final search information,
212 the the GUI has the complete statistics about the last search.
215 this is needed for copyprotected engines. After the uciok command the engine can tell the GUI,
216 that it will check the copy protection now. This is done by "copyprotection checking".
217 If the check is ok the engine should sent "copyprotection ok", otherwise "copyprotection error".
218 If there is an error the engine should not function properly but should not quit alone.
219 If the engine reports "copyprotection error" the GUI should not use this engine
220 and display an error message instead!
221 The code in the engine can look like this
222 TellGUI("copyprotection checking\n");
223 // ... check the copy protection here ...
225 TellGUI("copyprotection ok\n");
227 TellGUI("copyprotection error\n");
230 this is needed for engines that need a username and/or a code to function with all features.
231 Analog to the "copyprotection" command the engine can send "registration checking"
232 after the uciok command followed by either "registration ok" or "registration error".
233 Also after every attempt to register the engine it should answer with "registration checking"
234 and then either "registration ok" or "registration error".
235 In contrast to the "copyprotection" command, the GUI can use the engine after the engine has
236 reported an error, but should inform the user that the engine is not properly registered
237 and might not use all its features.
238 In addition the GUI should offer to open a dialog to
239 enable registration of the engine. To try to register an engine the GUI can send
240 the "register" command.
241 The GUI has to always answer with the "register" command if the engine sends "registration error"
242 at engine startup (this can also be done with "register later")
243 and tell the user somehow that the engine is not registered.
244 This way the engine knows that the GUI can deal with the registration procedure and the user
245 will be informed that the engine is not properly registered.
248 the engine wants to send infos to the GUI. This should be done whenever one of the info has changed.
249 The engine can send only selected infos and multiple infos can be send with one info command,
250 e.g. "info currmove e2e4 currmovenumber 1" or
251 "info depth 12 nodes 123456 nps 100000".
252 Also all infos belonging to the pv should be sent together
253 e.g. "info depth 2 score cp 214 time 1242 nodes 2124 nps 34928 pv e2e4 e7e5 g1f3"
254 I suggest to start sending "currmove", "currmovenumber", "currline" and "refutation" only after one second
255 to avoid too much traffic.
258 search depth in plies
260 selective search depth in plies,
261 if the engine sends seldepth there must also a "depth" be present in the same string.
263 the time searched in ms, this should be sent together with the pv.
265 x nodes searched, the engine should send this info regularly
266 * pv <move1> ... <movei>
269 this for the multi pv mode.
270 for the best move/pv add "multipv 1" in the string when you send the pv.
271 in k-best mode always send all k variants in k strings together.
274 the score from the engine's point of view in centipawns.
276 mate in y moves, not plies.
277 If the engine is getting mated use negativ values for y.
279 the score is just a lower bound.
281 the score is just an upper bound.
283 currently searching this move
285 currently searching move number x, for the first move x should be 1 not 0.
287 the hash is x permill full, the engine should send this info regularly
289 x nodes per second searched, the engine should send this info regularly
291 x positions where found in the endgame table bases
293 the cpu usage of the engine is x permill.
295 any string str which will be displayed be the engine,
296 if there is a string command the rest of the line will be interpreted as <str>.
297 * refutation <move1> <move2> ... <movei>
298 move <move1> is refuted by the line <move2> ... <movei>, i can be any number >= 1.
299 Example: after move d1h5 is searched, the engine can send
300 "info refutation d1h5 g6h5"
301 if g6h5 is the best answer after d1h5 or if g6h5 refutes the move d1h5.
302 if there is norefutation for d1h5 found, the engine should just send
303 "info refutation d1h5"
304 The engine should only send this if the option "UCI_ShowRefutations" is set to true.
305 * currline <cpunr> <move1> ... <movei>
306 this is the current line the engine is calculating. <cpunr> is the number of the cpu if
307 the engine is running on more than one cpu. <cpunr> = 1,2,3....
308 if the engine is just using one cpu, <cpunr> can be omitted.
309 If <cpunr> is greater than 1, always send all k lines in k strings together.
310 The engine should only send this if the option "UCI_ShowCurrLine" is set to true.
314 This command tells the GUI which parameters can be changed in the engine.
315 This should be sent once at engine startup after the "uci" and the "id" commands
316 if any parameter can be changed in the engine.
317 The GUI should parse this and build a dialog for the user to change the settings.
318 Note that not every option needs to appear in this dialog as some options like
319 "Ponder", "UCI_AnalyseMode", etc. are better handled elsewhere or are set automatically.
320 If the user wants to change some settings, the GUI will send a "setoption" command to the engine.
321 Note that the GUI need not send the setoption command when starting the engine for every option if
322 it doesn't want to change the default value.
323 For all allowed combinations see the example below,
324 as some combinations of this tokens don't make sense.
325 One string will be sent for each parameter.
327 The option has the name id.
328 Certain options have a fixed value for <id>, which means that the semantics of this option is fixed.
329 Usually those options should not be displayed in the normal engine options window of the GUI but
330 get a special treatment. "Pondering" for example should be set automatically when pondering is
331 enabled or disabled in the GUI options. The same for "UCI_AnalyseMode" which should also be set
332 automatically by the GUI. All those certain options have the prefix "UCI_" except for the
333 first 6 options below. If the GUI get an unknown Option with the prefix "UCI_", it should just
334 ignore it and not display it in the engine's options dialog.
335 * <id> = Hash, type is spin
336 the value in MB for memory for hash tables can be changed,
337 this should be answered with the first "setoptions" command at program boot
338 if the engine has sent the appropriate "option name Hash" command,
339 which should be supported by all engines!
340 So the engine should use a very small hash first as default.
341 * <id> = NalimovPath, type string
342 this is the path on the hard disk to the Nalimov compressed format.
343 Multiple directories can be concatenated with ";"
344 * <id> = NalimovCache, type spin
345 this is the size in MB for the cache for the nalimov table bases
346 These last two options should also be present in the initial options exchange dialog
347 when the engine is booted if the engine supports it
348 * <id> = Ponder, type check
349 this means that the engine is able to ponder.
350 The GUI will send this whenever pondering is possible or not.
351 Note: The engine should not start pondering on its own if this is enabled, this option is only
352 needed because the engine might change its time management algorithm when pondering is allowed.
353 * <id> = OwnBook, type check
354 this means that the engine has its own book which is accessed by the engine itself.
355 if this is set, the engine takes care of the opening book and the GUI will never
356 execute a move out of its book for the engine. If this is set to false by the GUI,
357 the engine should not access its own book.
358 * <id> = MultiPV, type spin
359 the engine supports multi best line or k-best mode. the default value is 1
360 * <id> = UCI_ShowCurrLine, type check, should be false by default,
361 the engine can show the current line it is calculating. see "info currline" above.
362 * <id> = UCI_ShowRefutations, type check, should be false by default,
363 the engine can show a move and its refutation in a line. see "info refutations" above.
364 * <id> = UCI_LimitStrength, type check, should be false by default,
365 The engine is able to limit its strength to a specific Elo number,
366 This should always be implemented together with "UCI_Elo".
367 * <id> = UCI_Elo, type spin
368 The engine can limit its strength in Elo within this interval.
369 If UCI_LimitStrength is set to false, this value should be ignored.
370 If UCI_LimitStrength is set to true, the engine should play with this specific strength.
371 This should always be implemented together with "UCI_LimitStrength".
372 * <id> = UCI_AnalyseMode, type check
373 The engine wants to behave differently when analysing or playing a game.
374 For example when playing it can use some kind of learning.
375 This is set to false if the engine is playing a game, otherwise it is true.
376 * <id> = UCI_Opponent, type string
377 With this command the GUI can send the name, title, elo and if the engine is playing a human
378 or computer to the engine.
379 The format of the string has to be [GM|IM|FM|WGM|WIM|none] [<elo>|none] [computer|human] <name>
381 "setoption name UCI_Opponent value GM 2800 human Gary Kasparow"
382 "setoption name UCI_Opponent value none none computer Shredder"
386 The option has type t.
387 There are 5 different types of options the engine can send
389 a checkbox that can either be true or false
391 a spin wheel that can be an integer in a certain range
393 a combo box that can have different predefined strings as a value
395 a button that can be pressed to send a command to the engine
397 a text field that has a string as a value,
398 an empty string has the value "<empty>"
400 the default value of this parameter is x
402 the minimum value of this parameter is x
404 the maximum value of this parameter is x
406 a predefined value of this parameter is x
408 Here are 5 strings for each of the 5 possible types of options
409 "option name Nullmove type check default true\n"
410 "option name Selectivity type spin default 2 min 0 max 4\n"
411 "option name Style type combo default Normal var Solid var Normal var Risky\n"
412 "option name NalimovPath type string default c:\\n"
413 "option name Clear Hash type button\n"
420 This is how the communication when the engine boots can look like:
424 // tell the engine to switch to UCI mode
431 // engine sends the options it can change
432 // the engine can change the hash size from 1 to 128 MB
433 option name Hash type spin default 1 min 1 max 128
435 // the engine supports Nalimov endgame tablebases
436 option name NalimovPath type string default <empty>
437 option name NalimovCache type spin default 1 min 1 max 32
439 // the engine can switch off Nullmove and set the playing style
440 option name Nullmove type check default true
441 option name Style type combo default Normal var Solid var Normal var Risky
443 // the engine has sent all parameters and is ready
446 // Note: here the GUI can already send a "quit" command if it just wants to find out
447 // details about the engine, so the engine should not initialize its internal
448 // parameters before here.
449 // now the GUI sets some values in the engine
451 setoption name Hash value 32
454 setoption name NalimovCache value 1
455 setoption name NalimovPath value d:\tb;c\tb
457 // waiting for the engine to finish initializing
458 // this command and the answer is required here!
461 // engine has finished setting up the internal values
464 // now we are ready to go
466 // if the GUI is supporting it, tell the engine that is is
467 // searching on a game that is hasn't searched on before
470 // if the engine supports the "UCI_AnalyseMode" option and the next search is supposted to
471 // be an analysis, the GUI should set "UCI_AnalyseMode" to true if it is currently
472 // set to false with this engine
473 setoption name UCI_AnalyseMode value true
475 // tell the engine to search infinite from the start position after 1.e4 e5
476 position startpos moves e2e4 e7e5
479 // the engine starts sending infos about the search to the GUI
480 // (only some examples are given)
483 info depth 1 seldepth 0
484 info score cp 13 depth 1 nodes 13 time 15 pv f1b5
485 info depth 2 seldepth 2
487 info score cp 14 depth 2 nodes 255 time 15 pv f1c4 f8c5
488 info depth 2 seldepth 7 nodes 255
489 info depth 3 seldepth 7
491 info score cp 20 depth 3 nodes 423 time 15 pv f1c4 g8f6 b1c3
496 // here the user has seen enough and asks to stop the searching
499 // the engine has finished searching and is sending the bestmove command
500 // which is needed for every "go" command sent to tell the GUI
501 // that the engine is ready again
502 bestmove g1f3 ponder d8f6