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Subject: Re: detecting blackades and draws through not advancing

Author: scott farrell

Date: 18:51:56 01/14/03

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On January 14, 2003 at 20:38:59, Dann Corbit wrote:

>On January 14, 2003 at 19:44:44, scott farrell wrote:
>>On January 14, 2003 at 16:28:45, Dann Corbit wrote:
>>Dan,
>>Firstly thanx for your interest on this.
>>No it doesnt solve it.
>>
>>Again its time to ply is slower, it get 1 ply less with the same time approx.
>>
>>Interestingly though, with the blockade code turned on when material<Queen, ie.
>>all positions in wac230, the score starts at +5 (mainly because of the 2 linked
>>passers +1 pawn up), but the score goes does each ply, failing low on most, so
>>after a few plies the score is down to +3.
>>
>>I think this is good, it didnt give a straight out draw, which it is not, with
>>the fiddling sort of move the rook around and defend etc, the score starts to
>>tend towards a draw. Given their are possibilities of moving pawns forward for
>>both sides, I think this is as good as I can expect from my code a this point.
>>
>>My chompster will score the move c3 after the sac as about an extra +4 to the
>>score, so immediately it wont think it got return on its sac, probably if I
>>pushed the eval of a linked passers higher, it would sac more quickly.
>
>That is one way that it can easily be solved.  However, it makes the programs
>play like crap.  If you run at "good playing strength" values for passed pawns,
>it is much harder to find.  Only crafty and ruffian solve it, that I remember.
>

Oh yeh, I agree, I didnt say i was going to change it, just was one way to solve
it.

It doesnt think the whole position is blocked, it just knows not to make it more
blocked.

>You could (perhaps) add to your algorithm a heuristic like this:
>
>1.  I am ahead on material
>2.  I detect a blockade
>3.  Boost passed pawns
>4.  Set value of breaking the blockade to my material advantage less 1 pawn.
>

yeh I like the ideas above.
I will have to think some more.
Maybe if during say during search of ply8 I detect x number or x% of blockades,
for ply9 I can adjust some values for passed pawns etc. But I think I run into
trouble with the hash table having older values, I need to think on it more.

>Some programs detect the problem (e.g. Hossa) but they don't know what to do
>about it, in order to solve it.
>
>>>How does your algorithm do on WAC.230?
>>>[D]2b5/1r6/2kBp1p1/p2pP1P1/2pP4/1pP3K1/1R3P2/8 b - - bm Rb4; id "WAC.230";



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