Author: Christophe Theron
Date: 01:12:28 01/25/99
Go up one level in this thread
On January 24, 1999 at 23:11:54, Robert Hyatt wrote:
>On January 24, 1999 at 18:41:13, Amir Ban wrote:
>
>>On January 24, 1999 at 17:31:15, Melvin S. Schwartz wrote:
>>
>>>I contacted a technical advisor from Saitek in Hong Kong who assured me that
>>>Brute Force was superior to Selective Search. His reason was that Brute Force
>>>searches more extensively and therefore minimizes the risk of an occasional
>>>oversight. Apparently the Selective Search is quicker but not as thorough.
>>
>>This can't be right in this day and age. Does Brute Force even exist any more,
>>other than in the initial implementations of amateurs ?
>>
>>I estimate that by making a decision to be brute-force (no forward pruning, no
>>extensions), you lose around 300-400 rating points to start with, meaning that
>>you won't score more than 15% or so against a strong program.
>
>I don't call brute force "no extensions". IE the original chess 4.0, which
>was the first successful brute-force program, had extensions for getting out
>of check, etc... as did we all back then.
But by doing extensions, you "select" some lines... You can view this as: you
prune some moves by looking at the history of moves that lead to the position.
The lines that have no extended moves are pruned earlier.
Extensions = A kind of selection ?
>I've always considered brute force to be 'no chess-knowledge-based forward
>pruning'. IE null-move is still a brute-force idea, although it stinks of
>selectivity when you look at what it is doing. But it is ignorant about the
>game of chess, generally, and works just as well in other games that don't have
>zug problems...
Null move pruning uses chess-dependant knowledge: the fact that generally there
exists a move that is better than doing nothing. As you stated, this would not
apply to any game. For example this does not work in Othello/Reversi...
Null move also relies on the fact that to create and identify an additional
threat in chess you (generally) need at least 2 more plies (hence the popular
R=2). This fact is often overlooked.
So I would say that the null move pruning idea uses at least 2 kind of chess
related knowledge.
>from that perspective, the Saitek guy was probably 1/2 right... because I think
>the 'good commercial programs' are brute force early and selective later.
>where 'early' is close to the root, and 'later' is closer to the leaves.
>
>I call 'selective' a program like my original chess program where we did a _lot_
>of plausibility analysis and weeded the ply-1 move list from N down to 6-9 moves
>max... ditto for every ply in the tree. _that_ is selective. :) and _very_
>dangerous too... :)
After all this time I realize that we don't have a clear definition of what
"selectivity" really means!!!
Are extensions (or reductions) a kind of selectivity ?
Is null move a real selective algorithm ?
Isn't a standard quiescence search a kind of selective search ?
Christophe
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