Author: Stefan Meyer-Kahlen
Date: 05:21:09 04/16/04
Go up one level in this thread
On April 16, 2004 at 06:40:47, Fabien Letouzey wrote:
>On April 16, 2004 at 06:17:51, Stefan Meyer-Kahlen wrote:
>
>>Hello Fabien,
>
>>On April 16, 2004 at 05:32:17, Fabien Letouzey wrote:
>
>>>Hello Stefan,
>
>>>I thought I had understood the UCI+ specifications, but a user reported to me
>>>that a "bestmove 0000" was sent by Shredder. It is true that a 50-move draw
>>>could be claimed in that specific case, but I was not at all expecting to
>>>receive a null move as "bestmove".
>
>>Oh, did Shredder really do that? :-)
>
>>This should not happen for a "normal" position. Do you have the position handy?
>>I assume that is was a position with no legal move left.
>
>>>Could you make a clarification about that issue (e.g. the interface must never
>>>send an "already-draw" position, or 0000 is an acceptable best move???)?
>
>>The proper solution would be not to send games with no move left.
>
>>Stefan
>
>Absolutely, but there was at least one legal move in the position.
>However, as I said, at least 100 reversible plies had been played before.
>So I thought "Shredder knows a draw should have been claimed, therefore it
>refuses to search". I just did not like receiving an illegal move as "bestmove"
>:)
>
>I have only partial information, but it appears that the user started with a
>made up position (KBNK, without tablebases). So "position fen ... moves ..."
>was used, maybe the behaviour can never happen with a guenuine game
>("startpos").
>
>Here is an extract of my log file; '>' means sent to the engine and '<' received
>from it. Unfortunately the user cut the line and inserted "..." instead, but I
>know there were at least 100 plies. I have just asked him for a complete log
>file by email, but I expect him not to have it anymore.
>
>---
>
>> ENGINE position fen 8/8/8/8/8/4k3/8/B3K2N w - - 0 1 moves h1f2 e3f4 ...
>> ENGINE go wtime 24960 btime 55850
>< ENGINE bestmove 0000
>
>---
>
>Don't worry about that specific instance (sorry I did not know a made-up
>position was used, I thought it was a normal game). All I need to know is that
>"bestmove" should not be followed by "0000" in normal circonstances, right?
Right. I have checked the code in the Shredder engine and it returns 0000 in
case you call it in a position
* with no legal move, so mate or stalemate
* with insufficient material left.
* with draw after 50 moves
in all those cases the engine should not be started by the GUI as in UCI the
draw and result handling is done by the GUI.
Stefan
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