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Subject: Re: Test position

Author: Robert Hyatt

Date: 08:30:02 07/20/04

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On July 20, 2004 at 04:29:32, Peter Berger wrote:

>On July 19, 2004 at 23:13:39, Robert Hyatt wrote:
>
>>On July 19, 2004 at 08:57:39, Tom Brake wrote:
>>
>>>r1b2R1R/pp1k4/8/P3p3/2n5/6P1/4KP2/8 w - - 0 31
>>>
>>>31. g4 wins.
>>
>>Crafty finds the right move quickly, a winning score takes a little longer...
>>
>>               12     2.16  -1.80   1. Rf6 Kc7 2. Rh7+ Bd7 3. a6 bxa6 4.
>>                                    Rxa6 Nb6 5. Ke3 Kc6 6. Ke4 Kd6 7. f4
>>                                    Bc6+ 8. Kf5 (s=8)
>>               13->   7.64  -1.44   1. g4 Kc7 2. g5 Bg4+ 3. Kd3 Rxf8 4.
>>                                    Rxf8 Nd6 5. g6 Bf5+ 6. Rxf5 Nxf5 7.
>>                                    Ke4 Ne7 8. g7 Kd6 9. f4 (s=2)
>
>What does s=8 or s=2 mean ?


S=2 means that the first two moves at the root should be searched one at a time,
by all processors (serial search = 2 is the meaning).  This is done when it
appears that based on the nodes searched for each root move, the second root
move has a node count that is very high compared to moves 3-n, and it appears
that it might become the best move with a deeper search.

In that case I want to use all processors to search that single move and get the
score, before I split the search at the root and use one processor per move.  If
I did that, the new best move would take a long time to search using a single
processor, adding to search overhead and perhaps making it impossible to get the
fail high before running out of time.  S=8 means 8 moves are close to each other
in terms of the size of the tree they produce, and each will be searched,
serially, using all processors on each.



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