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Subject: Re: What Does the Engine Do When User Sets Maximum Ply Depth?

Author: Bob Durrett

Date: 10:36:57 01/30/04

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On January 30, 2004 at 13:20:47, Robert Hyatt wrote:

>On January 30, 2004 at 12:05:30, Bob Durrett wrote:
>
>>
>>A friend is playing games against his chess-playing program on his PC and asked
>>this question.  I do not know the answer.
>>
>>Suppose the user sets the ply depth to 5 ply.  There are several things the
>>engine could do in that case, assuming in the middlegame.
>>
>>If sufficient time were available:
>>
>>The entire tree could be exhaustively analyzed.
>
>I am not sure what that means...

I guess I was not too clear.  Sorry about that.

I envisioned "un-pruning."  In the beginning the engine does not know how much
time the user will allow.  Perhaps the programmer can decide this, but surely
the engine must consider the possibility that the user will issue a "move now"
command.  Hence, I would expect pruning so that the engine would have a move
available almost immediately.  Then, as more time were made available, the
engine could go back and consider previously pruned portions of the tree.

>
>>
>>The position evaluation could be done more extensively/thoroughly.
>
>
>Nor that since the normal Evaluation() stuff is done at appropriate points
>inside the tree already.  There's no other places where it could be done..

Again, I did not make myself clear.  Sorry again!

My thought was that the programmer will give the position evaluation a limited
amount of time to do it's work.  This might be accomplished simply by making the
position evaluation code be "fast."

If more time became available, however, maybe the position evaluations could be
revisited and a more time-consuming [hence, presumably, better] evaluation be
done.

>
>
>>
>>Do any engines to the above?  Or, do they just stop prematurely?


>>
>>Bob D.
>
>
>If "prematurely" means "when you said to stop" then I guess the answer is they
>stop "prematurely".  If you say "5 plies" they do 5 plies and that's all...


My choice of the word "prematurely" may have been premature.  : )

The idea was that "haste makes waste" in real life as well as in software.
Software designed to reach an answer, or result, in a very short time may be
compromised in some way.  That does not mean that the number of positions
evaluated be reduced [although that could happen with a "move now" command] but
rather that position evaluations would have to be done quicker than what would
be ideal.

Bob D.



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