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Subject: Re: Ruffian's blind spot

Author: Uri Blass

Date: 03:22:22 05/20/03

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On May 20, 2003 at 03:50:58, Tony Werten wrote:

>On May 20, 2003 at 02:17:14, Tim Foden wrote:
>
>>On May 19, 2003 at 23:46:58, Will Singleton wrote:
>>
>>>I was trying to figure out why my latest build doesn't do quite as well on
>>>ecm86, and I ran Ruffian on it.  To my surprise, Ruffian couldn't solve it, even
>>>given 5 minutes.  This is odd, since most other progs can do it in less than 10
>>>seconds.  (What I take away from this exercise is that my program must now be
>>>stronger.  Otherwise, I'd have to work on the problem, which is much less
>>>interesting than testing new ideas.)
>>>
>>>[D]2r3k1/1nqbrp2/p5pp/1p1Pp1N1/8/1P5P/P1B2PP1/2RQR1K1 w - -
>>
>>I would assume then (from running Green Light), that Nxf7 is the correct move
>>here?
>>
>>The PV is interesting as it contains 9 captures in a row at the start of the PV.
>> Maybe ruffian is pruning if there are more than a certain number of captures in
>>a row (as this is very unlikely to be a good thing).
>
>My guess is that Ruffian is a preprocessor, which can't handle 9 captures
>because the position is so different ( root position compared to leaf position )
>
>There is a good chance Fritz 5.32 will show the same beheavior.
>
>Tony

Your guess seems to be wrong and if I do the moves Nxf7 Rxf7 and take them back
Ruffian has no problem to find Nxf7.

Fritz5.32 also has no problem with that move.
I believe that being preprocessor is a bad idea so my default assumption(unless
other things are provedO) is that Ruffian is not a preprocessor.

I guess that some pruning that is not null move pruning prevents it to see Nxf7
in a reasonable time.

Uri



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