UCI protocol: giving up!

[flok]

Hi,

While implementing UCI I noticed it is not specified what the engine should report when it cannot do a move.
I do not mean in a checkmate situation but for example when it would encounter a 3-repeats move.
http://www.shredderchess.com/chess-info ... rface.html doesn't specify it, it seems

[ZirconiumX]

The GUI should handle that - so don't worry.

If the GUI dows send a go command for a threefold rep then send bestmove 0000.

Matthew:out

[mar]

Hi,

While implementing UCI I noticed it is not specified what the engine should report when it cannot do a move.
I do not mean in a checkmate situation but for example when it would encounter a 3-repeats move.
http://www.shredderchess.com/chess-info ... rface.html doesn't specify it, it seems

Why? The GUI should never send an illegal move. And when you do a root search you should ignore all draws by repetition and stuff like that. The engine must output a move whenever it's asked to.
Hope that helps and don't give up!

Martin

[flok]

Ok, that's what I'll do.
I think I'll give it a penalty to the score instead.

[Sven]

Ok, that's what I'll do.
I think I'll give it a penalty to the score instead.

There is no need even for such a penalty. If the GUI sends "go" but there is no legal move in the root position (mate, stalemate) then send "bestmove 0000", as already proposed. If the GUI sends "go" in a position that could have been claimed as a draw by rule (50 moves rule, threefold repetition, insufficient material) but was actually not claimed then do a normal search and ignore the behaviour of the GUI. This does also not change anything for your normal draw detection within the search, so you might actually return a best move that enforces a draw by 50 moves rule, for instance.

Sven

[hgm]

UCI specs allow you to send a null move. The GUI would understand from this that you don't want to move (if it is any good, that is..).

In the score you could specify whether you think this makes the game end in a win, loss or draw. For instance, if you are checkmated in the current position, it would make sense to think that you will lose this game, and report -M0. If you let the engine refuse to play on after a 3-fold rep, it would make sense to report a draw score.

Of course I would not recommend anyone to use UCI at all.

[lucasart]

Hi,

While implementing UCI I noticed it is not specified what the engine should report when it cannot do a move.
I do not mean in a checkmate situation but for example when it would encounter a 3-repeats move.
http://www.shredderchess.com/chess-info ... rface.html doesn't specify it, it seems

and why would you ever end up in this situation ? If it happens it means the GUI is buggy!

[lucasart]

Of course I would not recommend anyone to use UCI at all.

Nor would I recommend to anyone using the Xboard protocol

[lucasart]

The GUI should handle that - so don't worry.

If the GUI dows send a go command for a threefold rep then send bestmove 0000.

Matthew:out

yes, i guess it's the only thing that would make sense. but we're talking about a hypothetical situation that would never happen.
alternatively you could just exit the program with an error code, and dump a message in stderr, saying the GUI is sending illegal moves...

[lucasart]

Hi,

While implementing UCI I noticed it is not specified what the engine should report when it cannot do a move.
I do not mean in a checkmate situation but for example when it would encounter a 3-repeats move.
http://www.shredderchess.com/chess-info ... rface.html doesn't specify it, it seems

The most basic implementation of UCI you should do is as follows:
* when you recieve "uci" just answer "uciok"
* be prepared to handle position commands, eg.
position startpos moves e2e4 c7c5
position fen ... moves d4e5
* be prepared to handle go commands, there are several types of parameters to limit the search (time+inc, time, depth, nodes etc.). the most simple one is a fixed time per move (in ms)
go movetime 1000
so now you do a 1sec search, and return something like
bestmove e2e4

and that's all you need to get started !

Also your program will benefit from the book of the GUI. One of the many advantages of UCI vs Xboard