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Subject: Re: Unstable aspiration search

Author: Robert Hyatt

Date: 19:43:58 02/11/03

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On February 11, 2003 at 18:50:42, Sune Fischer wrote:

>On February 11, 2003 at 15:58:13, Robert Hyatt wrote:
>
>>I'm not sure whether you still want me to play with the aspiration window
>>and post results or not.   I ran this on my laptop and got Nb3 every time,
>>with a score of about -1.0:
>>
>>                7->   1.60  -1.03   1. Nb3 Qf6 2. Bb2 Bf3 3. Qd3 Qc6 4.
>>                                    e4
>>                8     2.42  -1.13   1. Nb3 exd4 2. Nxd4 c5 3. bxc5 Nxc5
>>                                    4. Bd2 Bc4 5. Re1 Qf6
>>                8->   3.10  -1.13   1. Nb3 exd4 2. Nxd4 c5 3. bxc5 Nxc5
>>                                    4. Bd2 Bc4 5. Re1 Qf6
>>                9     6.81  -0.96   1. Nb3 exd4 2. Nxd4 c5 3. bxc5 Nxc5
>>                                    4. Bd2 Ne6 5. Nxe6 Qxe6 6. Rc1
>>                9->   7.60  -0.96   1. Nb3 exd4 2. Nxd4 c5 3. bxc5 Nxc5
>>                                    4. Bd2 Ne6 5. Nxe6 Qxe6 6. Rc1
>>               10    18.36  -1.19   1. Nb3 Qf6 2. Bd3 Qh4 3. Bxb5 Qxh3
>>                                    4. f3 Nb8 5. dxe5 Qg3+ 6. Kh1 Bxe5
>>               10->  22.43  -1.19   1. Nb3 Qf6 2. Bd3 Qh4 3. Bxb5 Qxh3
>>                                    4. f3 Nb8 5. dxe5 Qg3+ 6. Kh1 Bxe5
>>              time=23.28  cpu=99%  mat=0  n=8188457  fh=91%  nps=351k
>>
>>
>>If you want me to run with different aspiration windows, let me know...
>
>Just a quick question. What happens if you run with material eval only?
>Does this increase instability?
>
>It does in my case.
>
>-S.


Define "instability".  Score changes?  If it does, you must have a bug.  But
it should be possible to get somewhat different PVs if your move ordering is
not deterministic...  ie dependent on alpha/beta values.  But that would be
because all moves that don't lose material get scored as zero by the search...



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