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Subject: Re: Positional/Real Sacrifice

Author: blass uri

Date: 02:48:26 12/01/99

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On December 01, 1999 at 03:42:20, Ricardo Gibert wrote:

>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.

I do not agree that Rebel is too optimistic after 3 plies.

Uri



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