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Subject: Re: Extension of the UCI protocol

Author: Stefan Meyer-Kahlen

Date: 11:41:53 04/17/04

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On April 17, 2004 at 02:58:10, Andrey Popov wrote:

>I have two questions:
>
>>* The engine should boot and wait for input from the GUI,
>>  the engine should wait for the "isready" or "setoption" command to set up its
>>  internal parameters as the boot process should be as quick as possible.
>>
>When should an engine verify the presence of all its parts (dlls etc.)
>and tell to GUI an error message if something is absent?
>
>>* multipv <num>
>>this for the multi pv mode.
>>for the best move/pv add "multipv 1" in the string when you send the pv.
>>in k-best mode always send all k variants in k strings together.
>>
>As far as I understood, the engine must silently accumulate
>the information (pv,score etc.) about all moves.
>At the end of each ply the engine must sort all these moves by score
>and send to the GUI something like the following:
>info multipv 1 depth 2 score 25 time 100 nodes 33000 nps 33 pv e2e4 e7e5
>info multipv 2 depth 2 score 23 time 100 nodes 33000 nps 33 pv d2d4 g8f6
>info multipv 3 depth 2 score 22 time 100 nodes 33000 nps 33 pv c2c4 c7c5
>All "time","nodes" and "nps" must from the end of the ply.
>Therefore, they must be equal for all moves. Am I right?


No, they are different. If you search a move and find out, that it is one of the
k best, you just send the lines of your k best moves so far.

Example:

At depth 4 you have searched e3 and d3 and those are your two best moves, so you
send:

info multipv 1 depth 4 seldepth 7 time 29 score cp 6 nodes 1120 pv e2e3 g8f6
info multipv 2 depth 4 seldepth 7 time 31 score cp 5 nodes 773 pv d2d3 b8c6

Now you start with depth 5. After searching e3 there, you display the lines of
your two best moves so far.

info multipv 1 depth 5 seldepth 9 time 129 score cp 8 nodes 13420 pv e2e3 e7e6
info multipv 2 depth 4 seldepth 7 time 31 score cp 5 nodes 773 pv d2d3 b8c6

If e3 gets a fail low it is still your best move at this ply as you haven't
searched any other move there. So the display above changes to

info multipv 1 depth 5 seldepth 9 time 129 score cp -99 nodes 13420 pv e2e3 e7e6
info multipv 2 depth 4 seldepth 7 time 31 score cp 5 nodes 773 pv d2d3 b8c6


Stefan



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