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Subject: Re: Positional/Real Sacrifice

Author: Ricardo Gibert

Date: 00:42:20 12/01/99

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On November 30, 1999 at 22:19:28, Robert Hyatt wrote:

>On November 30, 1999 at 19:49:44, Alexander Kure wrote:
>
>>On November 30, 1999 at 17:45:23, Robert Hyatt wrote:
>>
>>>On November 30, 1999 at 04:40:20, Ed Schröder wrote:
>>>
>>>>On November 30, 1999 at 04:12:22, Jeremiah Penery wrote:
>>>>
>>>>>On November 30, 1999 at 03:35:54, Ed Schröder wrote:
>>>>>
>>>>>>As said we must have a different view on king safety even on the basics as
>>>>>>this case for me is so crystal clear: QRRB all pointed at a naked king, the
>>>>>>king having hardly any escapes,
>>>>>
>>>>>True, but all it takes to wreck the whole thing is ONE escape for the black
>>>>>king, as long as black doesn't lose material doing it.  In this case, I don't
>>>>>think there is an escape, but it will happen in other positions.
>>>>
>>>>And SEARCH will filter that.
>>>>
>>>>Ed
>>>
>>>not at 1-2-3 plies it won't.  If you don't see the escape, you make the
>>>sac. If I don't see the win, I don't make it. That is a subtle difference.
>>>You want the search to refute the positional sac.  I want the search to justify
>>>the sac...
>>
>>
>>You cannot justify anything with a 1-2-3 ply search. But after 5-7 plies it
>>should be clear that Bxh6 is winning, providing your king safety/attack is well
>>implemented:
>>
>>2-3 pawns + dead opponent's king > bishop, but if "dead opponent's king" -> 0 in
>>your evaluation this inequality busts.
>>
>>Nimzo 7.32 for example has a very limited concept of king safety and does not
>>find Bxh6 after 10 plies!
>>
>>Greetings
>>Alex
>
>
>You are missing the point.  Rebel liked things after Bxh6 gxh6 Qxh6.  What
>happens if it gives up a pawn at ply-1, so that it can force this position
>at ply=10?  Now it can't search beyond the above sequence, and it chooses to
>enter this based on that 1 ply search.  And by the time you discover that it
>doesn't work, you are already 'in for a pawn..."
>
>what to do then???

Yes. After 3 plies, Rebel is too optimistic, but after 5 plies crafty is too
pessimistic. Both programs need work on their evals.




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