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Subject: Re: What to do with Horizon effect?

Author: Robert Hyatt

Date: 10:23:31 11/03/98

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On November 03, 1998 at 07:15:57, Inmann Werner wrote:

>>>*********
>>>I tried something with null move.
>>>
>>>Problem: you can make a mate with the next move, but the opponent checks you as
>>>long as it goes beyond the horizon.
>>>I now only talk about this specific problem. I think, it often occurs and know,
>>>that a "solution" for this problem does not stop horizon effect all.
>>>
>>>My thought: When the opponent is on move, I do a null move and one own move and
>>>then quiet search. If a mate occurs here, I remember it, and pass it to the next
>>>alpha_beta recursion which is my move. Only if a am checked at this time, I
>>>extend 2 moves (not only one for the check) as long as extensions are allowed.
>>>(Max Extensions...)
>>>So I only extend if I can mate in one and the opponent slides out with a check!
>>>There are also some limitations when doing the special null move, but there I am
>>>experimating.
>>>
>>>My position above then gets solved at ply 6!!!!!
>>>I tried some other positions with heavy threats and checks, where no real mate
>>>can be made (worse for my algoritm). There it slows down about 10%, because it
>>>looks deeper in maybe interesting things which in this case do not work.
>>>
>>>I must say, that I implemented above 3 hours ago, and 3 hours testing is not
>>>much, but it is worth to think about.
>>>
>>>Werner
>>
>>
>>my advice is "caution" doing this.  IE Crafty finds this at depth=10, about
>>10 seconds or so on my ALR.  It's not hard to make it find it at depth=6 or
>>7.  But would it play better in games?  No...  it is *easy* to over-extend and
>>find wonderful tactics but get killed positionally...
>
>But that would be a principle problem of extensions. If I do not extend in any
>case, I can fasten up my program extremly, getting 1 ply deeper.
>The question is, when to extend.
>Many say, at checks and beats on the same field, because here it gets
>interesting.
>I do so, and the search slows down. Gets the program then a worse play?
>Same I thought about mate threats and extensions. ArenĀ“t they worth an
>extension?
>
>Werner

Here's my "stock answer" to that question:  Doing the *right* extensions is
critical.  Doing extensions in the wrong places is futile.  You simply try to
shift the balance toward doing them in the "right places" only...  if you
do a few extra, it only costs you time.  If you miss a "right place" it can
cost you the game.  And finally, if you do too many in the wrong place, that
can *also* cost you the game...

sort of like Goldilocks and the three bears... it has to be done "just right"
to make everyone happy.. :)



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