Author: Robert Hyatt
Date: 10:41:36 07/23/02
Go up one level in this thread
On July 23, 2002 at 09:41:10, Ed Schröder wrote:
>On July 22, 2002 at 14:11:23, Robert Hyatt wrote:
>
>>On July 22, 2002 at 11:52:35, Ed Schröder wrote:
>>
>>>The two you entirely miss the point of Kasparov's suspicion, sigh...
>>>
>>>Lesson 61, now pay attention my pupils :)
>>>
>>>[d]r1r1q1k1/6p1/p2b1p1p/1p1PpP2/PPp5/2P4P/R1B2QP1/R5K1 w - - id DEEP BLUE -
>>>Kasparov,G;
>>>
>>>Position before 36.axb5
>>>
>>>Here DB for a long time showed the following main-line:
>>>
>>>36.Qb6 Qe7 37.axb5 Rab8 38.Qxa6 e4 39.Bxe4 Qe5 40.Bf3 Rcd8 41.Qa7 Qc3 42.Bh5
>>>
>>>Now let's have a look at the main-line shall we?
Here is a possible line (from crafty) after Qb6:
36. Qb6 Qf8 37. axb5 axb5 38. Qxb5
Rab8 39. Qd7 Rc7 40. Qa4 Qf7 41. Be4
Qh5 42. Qc2 Qg5 43. Ra8 Rb7 44. Rxb8+
Rxb8 45. Ra7
And here is one after axb5:
36. axb5 axb5 37. Be4 Rxa2 38. Qxa2
Rb8 39. Qa6 Qd7 40. Kh2 Kf7 41. Qc6
Ke7 42. Qxd7+ Kxd7 43. Ra7+ Bc7 44.
Kg3 Rg8 45. h4 Kd6 46. h5 Re8
>>>
>>>After 39...Qe5 we get:
>>>
>>>[d]1rr3k1/6p1/Q2b1p1p/1P1PqP2/1Pp1B3/2P4P/R5P1/R5K1 w - -
>>>
>>>As you can see black has sacrificed 3 (!!) pawns for a king attack. And this my
>>>pupils is what Kasparov could not believe, a computer sacrificing 3 pawns and so
>>>he started asking questions how that could be.
As you see above, it is not necessary for anybody to sacrifice anything after
white plays either of the two moves... So I don't quite get the 3 pawn issue
since we don't really know if the DB pv means a thing. Remember that they
had 30 processors searching different parts of the tree, with no shared hash
table. How do you reconstruct a PV from hash, when you get different best
moves from different processors, when you ask them to probe their hash tables
to see what was best in a given position? DB pvs always had odd moves here
and there because of this. I tried it a _long_ while back and immediately gave
up on it because the PVs were not completely reliable. Of course, Kasparov did
not have access to DB's PV anyway so he couldn't have known what they were
"thinking". He only had _his_ analysis for the two moves to claim that Qb6
was far better...
In the position for white's move 36, material is even. Crafty sees (after a 30
minute search so far after the re-start) winning a pawn with Qb6. It doesn't
see winning anything but some positinal edges with axb5. But it hasn't gotten
deep enough to get the scores closer yet. That will take a while.
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