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Subject: Re: Fine 70 same 7 engines (more)

Author: Rafael Andrist

Date: 13:08:03 09/11/01

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On September 11, 2001 at 15:02:36, Robert Hyatt wrote:

>On September 11, 2001 at 11:40:22, Rafael Andrist wrote:
>
>>On September 11, 2001 at 10:36:00, Robert Hyatt wrote:
>>
>>>On September 10, 2001 at 13:37:58, Rafael Andrist wrote:
>>>
>>>>On September 07, 2001 at 13:41:57, Robert Hyatt wrote:
>>>>
>>>>>I did this in Cray Blitz _many_ years ago (coordinated squares is the term I
>>>>>hear used most often).  And I was amazed that it took longer to find the right
>>>>>move.  After a mountain of debugging output, I discovered what I mentioned
>>>>>previously...  "hash grafting" (the art of grafting parts of the tree from
>>>>>one zone to another by using the hash table) was helping the dumber version,
>>>>>but not the smarter one.
>>>>>
>>>>
>>>>You mix some things together! Knowledge about opposition is only one of the
>>>>tools you need to to construct a system of co-ordinated squares (german:
>>>>Gegenfeldsystem). If you implement this correctly, you should find the correct
>>>>move instantly i.e at ply 1 as my chess program Wilhelm does.
>>>>
>>>>Rafael B. Andrist
>>>
>>>
>>>You find the right move instantly...  But you don't _know_ it is the right move
>>>until the score jumps.  It _could_ just be a draw.  And in the case of Cray
>>>Blitz, using coordinated squares, it took 25-26 plies to see the big score.
>>>It saw the right move normally at around ply=18 with the +2.5 score.  With
>>>the coordinated squares stuff, it got the Kb1 move instantly, but the score
>>>didn't reach +2.5 until 7-8 plies longer than the simple version.
>>>
>>>That was the point.  The better the move ordering, the less "grafting" helps
>>>a shallow search find a deep solution.
>>
>>I now by eval from ply 1 that i win a pawn. In Fine 70, White is already a pawn
>>up, so I get instantly an evaluation around 2.
>>
>>Rafael B. Andrist
>
>
>How do you get +2 at ply=1 when you don't see the pawn being won?  Is this just
>a big positional score for always staying on a "coordinated square" with the
>black king?

If the kings are on the appropriate squares the win of the additional pawn is
simply forced. The only thing you must check are tactical counter-attacks out of
the system of co-ordinated squares. My implementation is slightly different from
the human understanding of co-ordinated squares. It is detected that the win of
the additional pawn is _guaranteed_. Of course it may be possible that a created
passer can be stopped by the opponent, but i get _exact_ knowledge concerning
the win of an additional pawn.

Note that co-ordinate squares is not distant opposition. The concept of distant
opposition works only in some trivial cases and can be done by simply counting
some distances.

Rafael B. Andrist



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