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Subject: Re: test position

Author: Ron Murawski

Date: 09:46:57 07/19/02

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On July 19, 2002 at 01:54:47, Steffen Jakob wrote:

>On July 18, 2002 at 23:52:40, Ron Murawski wrote:
>
>>On July 18, 2002 at 22:24:13, K. Burcham wrote:
>>
>>>
>>>here GM Timman 2623 FIDE played 14.Nxf6
>>>is there any program that prefers to exchange Knights at f6, instead of the pawn
>>>capture at e7?
>>>
>>>kburcham
>>>
>>>
>>>
>>> [D] rnbq1r2/4ppkp/p2p1np1/3N4/1p1N4/4Q2P/PPP2PP1/2KR1B1R w - - 0 1
>>
>>On a 1.8GHz AMD, it takes the latest Horizon beta 14.12 seconds to find Nb6.
>>Horizon agrees with Chessmaster that this is the best move.
>>
>>Depth Score   Time      Nodes   pv
>>  4     47      44      16293   Nxe7 Re8 Re1 Kh8
>>  4    115      44      16673   Nxf6 exf6 Qe4 Ra7
>>  4    128      49      17552   Nxb4 Kh8 Qh6 Ra7
>>  4    137      49      19005   Bc4 Kh8 Nxe7 Ra7
>>  5     79?     55      30021   Bc4 Bb7 Ne6+ fxe6 Bxa6
>>  5    115      60      35197   Nxb4 Kh8 Qf3 Ra7 Bc4
>>  5    142      60      41915   Nxe7 Bb7 Ndf5+ Kh8 Qh6 d5
>>  6    128      82     103073   Nxe7 Re8 Re1 Kh8 Bc4 Ra7
>>  7    111     143     279955   Nxe7 Re8 Re1 Bb7 f3 Be4 Bd3 Rxe7 fxe4
>>  8     82?    247     652614   Nxe7 Re8 Re1 Qc7 Qf3 Ra7 Kd2
>>  8     82     478    1481058   Nxe7 Kh8 Qf3 d5 Nxc8 Ng8
>>  9     61     604    1889811   Nxe7 Re8 Qf3 Rxe7 Qxa8 Bb7 Qa7 Bxg2 Qxe7 Qxe7
>>                                Bxg2
>>  9    111!   1412    4493054   Nb6 Qxb6 Nf5+ Bxf5 Qxb6 Bxh3 Rxh3
>                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>That is a weird PV!
>
>Greetings,
>Steffen.
>

Yes, it *is* a weird pv. I have noticed weird lines in Horizon's pv from time to
time, but they tend to get replaced quickly. Most of the time the first move in
the pv is correct, but every once and a while Horizon can lose a game due to
this. I suppose it is caused by search instabilities. I've been searching for
this bug for a long time. When I again try and find/fix this bug I will attempt
to choose a "better" sequence of 64-bit random numbers for my Zobrist hashing.
I'm running out of ideas as to the cause of the occasional pv weirdness.

Ron

>>  9    114    1648    5265170   Nb6 Bb7 Nxa8 Bxa8 Be2 Bxg2 Rhg1 Be4 Qg5
>> 10     89    2422    7893348   Nb6 Bb7 Nxa8 Bxa8 Kb1 e5 Nf3 Bxf3 Qxf3 d5
>> 11    117    5471   17568997   Nb6 Ra7 Nxc8 Rb7 Nxd6 exd6 Bc4 Rc7 Bb3
>>
>>Ron



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